proc

PROC(5)                    Linux Programmer's Manual                   PROC(5)



NAME
       proc - process information pseudo-file system

DESCRIPTION
       The proc file system is a pseudo-file system which is used as an
       interface to kernel data structures.  It is commonly mounted at /proc.
       Most of it is read-only, but some files allow kernel variables to be
       changed.

       The following outline gives a quick tour through the /proc hierarchy.

       /proc/[pid]
              There is a numerical subdirectory for each running process; the
              subdirectory is named by the process ID.  Each such subdirectory
              contains the following pseudo-files and directories.

       /proc/[pid]/auxv (since 2.6.0-test7)
              This contains the contents of the ELF interpreter information
              passed to the process at exec time.  The format is one unsigned
              long ID plus one unsigned long value for each entry.  The last
              entry contains two zeros.

       /proc/[pid]/cgroup (since Linux 2.6.24)
              This file describes control groups to which the process/task
              belongs.  For each cgroup hierarchy there is one entry
              containing colon-separated fields of the form:

                  5:cpuacct,cpu,cpuset:/daemons

              The colon-separated fields are, from left to right:

                  1. hierarchy ID number

                  2. set of subsystems bound to the hierarchy

                  3. control group in the hierarchy to which the process
                     belongs

              This file is present only if the CONFIG_CGROUPS kernel
              configuration option is enabled.

       /proc/[pid]/cmdline
              This holds the complete command line for the process, unless the
              process is a zombie.  In the latter case, there is nothing in
              this file: that is, a read on this file will return 0
              characters.  The command-line arguments appear in this file as a
              set of strings separated by null bytes ('\0'), with a further
              null byte after the last string.

       /proc/[pid]/coredump_filter (since kernel 2.6.23)
              See core(5).

       /proc/[pid]/cpuset (since kernel 2.6.12)
              See cpuset(7).

       /proc/[pid]/cwd
              This is a symbolic link to the current working directory of the
              process.  To find out the current working directory of process
              20, for instance, you can do this:

                  $ cd /proc/20/cwd; /bin/pwd

              Note that the pwd command is often a shell built-in, and might
              not work properly.  In bash(1), you may use pwd -P.

              In a multithreaded process, the contents of this symbolic link
              are not available if the main thread has already terminated
              (typically by calling pthread_exit(3)).

       /proc/[pid]/environ
              This file contains the environment for the process.  The entries
              are separated by null bytes ('\0'), and there may be a null byte
              at the end.  Thus, to print out the environment of process 1,
              you would do:

                  $ strings /proc/1/environ

       /proc/[pid]/exe
              Under Linux 2.2 and later, this file is a symbolic link
              containing the actual pathname of the executed command.  This
              symbolic link can be dereferenced normally; attempting to open
              it will open the executable.  You can even type /proc/[pid]/exe
              to run another copy of the same executable as is being run by
              process [pid].  In a multithreaded process, the contents of this
              symbolic link are not available if the main thread has already
              terminated (typically by calling pthread_exit(3)).

              Under Linux 2.0 and earlier /proc/[pid]/exe is a pointer to the
              binary which was executed, and appears as a symbolic link.  A
              readlink(2) call on this file under Linux 2.0 returns a string
              in the format:

                  [device]:inode

              For example, [0301]:1502 would be inode 1502 on device major 03
              (IDE, MFM, etc. drives) minor 01 (first partition on the first
              drive).

              find(1) with the -inum option can be used to locate the file.

       /proc/[pid]/fd/
              This is a subdirectory containing one entry for each file which
              the process has open, named by its file descriptor, and which is
              a symbolic link to the actual file.  Thus, 0 is standard input,
              1 standard output, 2 standard error, etc.

              For file descriptors for pipes and sockets, the entries will be
              symbolic links whose content is the file type with the inode.  A
              readlink(2) call on this file returns a string in the format:

                  type:[inode]

              For example, socket:[2248868] will be a socket and its inode is
              2248868.  For sockets, that inode can be used to find more
              information in one of the files under /proc/net/.

              For file descriptors that have no corresponding inode (e.g.,
              file descriptors produced by epoll_create(2), eventfd(2),
              inotify_init(2), signalfd(2), and timerfd(2)), the entry will be
              a symbolic link with contents of the form

                  anon_inode:<file-type>

              In some cases, the file-type is surrounded by square brackets.

              For example, an epoll file descriptor will have a symbolic link
              whose content is the string anon_inode:[eventpoll].

              In a multithreaded process, the contents of this directory are
              not available if the main thread has already terminated
              (typically by calling pthread_exit(3)).

              Programs that will take a filename as a command-line argument,
              but will not take input from standard input if no argument is
              supplied, or that write to a file named as a command-line
              argument, but will not send their output to standard output if
              no argument is supplied, can nevertheless be made to use
              standard input or standard out using /proc/[pid]/fd.  For
              example, assuming that -i is the flag designating an input file
              and -o is the flag designating an output file:

                  $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...

              and you have a working filter.

              /proc/self/fd/N is approximately the same as /dev/fd/N in some
              UNIX and UNIX-like systems.  Most Linux MAKEDEV scripts
              symbolically link /dev/fd to /proc/self/fd, in fact.

              Most systems provide symbolic links /dev/stdin, /dev/stdout, and
              /dev/stderr, which respectively link to the files 0, 1, and 2 in
              /proc/self/fd.  Thus the example command above could be written
              as:

                  $ foobar -i /dev/stdin -o /dev/stdout ...

       /proc/[pid]/fdinfo/ (since kernel 2.6.22)
              This is a subdirectory containing one entry for each file which
              the process has open, named by its file descriptor.  The
              contents of each file can be read to obtain information about
              the corresponding file descriptor, for example:

                  $ cat /proc/12015/fdinfo/4
                  pos:    1000
                  flags:  01002002

              The pos field is a decimal number showing the current file
              offset.  The flags field is an octal number that displays the
              file access mode and file status flags (see open(2)).

              The files in this directory are readable only by the owner of
              the process.

       /proc/[pid]/io (since kernel 2.6.20)
              This file contains I/O statistics for the process, for example:

                  # cat /proc/3828/io
                  rchar: 323934931
                  wchar: 323929600
                  syscr: 632687
                  syscw: 632675
                  read_bytes: 0
                  write_bytes: 323932160
                  cancelled_write_bytes: 0

              The fields are as follows:

              rchar: characters read
                     The number of bytes which this task has caused to be read
                     from storage.  This is simply the sum of bytes which this
                     process passed to read(2) and similar system calls.  It
                     includes things such as terminal I/O and is unaffected by
                     whether or not actual physical disk I/O was required (the
                     read might have been satisfied from pagecache).

              wchar: characters written
                     The number of bytes which this task has caused, or shall
                     cause to be written to disk.  Similar caveats apply here
                     as with rchar.

              syscr: read syscalls
                     Attempt to count the number of read I/O operations—that
                     is, system calls such as read(2) and pread(2).

              syscw: write syscalls
                     Attempt to count the number of write I/O operations—that
                     is, system calls such as write(2) and pwrite(2).

              read_bytes: bytes read
                     Attempt to count the number of bytes which this process
                     really did cause to be fetched from the storage layer.
                     This is accurate for block-backed filesystems.

              write_bytes: bytes written
                     Attempt to count the number of bytes which this process
                     caused to be sent to the storage layer.

              cancelled_write_bytes:
                     The big inaccuracy here is truncate.  If a process writes
                     1MB to a file and then deletes the file, it will in fact
                     perform no writeout.  But it will have been accounted as
                     having caused 1MB of write.  In other words: this field
                     represents the number of bytes which this process caused
                     to not happen, by truncating pagecache.  A task can cause
                     "negative" I/O too.  If this task truncates some dirty
                     pagecache, some I/O which another task has been accounted
                     for (in its write_bytes) will not be happening.

              Note: In the current implementation, things are a bit racy on
              32-bit systems: if process A reads process B's /proc/[pid]/io
              while process B is updating one of these 64-bit counters,
              process A could see an intermediate result.

       /proc/[pid]/limits (since kernel 2.6.24)
              This file displays the soft limit, hard limit, and units of
              measurement for each of the process's resource limits (see
              getrlimit(2)).  Up to and including Linux 2.6.35, this file is
              protected to allow reading only by the real UID of the process.
              Since Linux 2.6.36, this file is readable by all users on the
              system.

       /proc/[pid]/map_files/ (since kernel 3.3)
              This subdirectory contains entries corresponding to memory-
              mapped files (see mmap(2)).  Entries are named by memory region
              start and end address pair (expressed as hexadecimal numbers),
              and are symbolic links to the mapped files themselves.  Here is
              an example, with the output wrapped and reformatted to fit on an
              80-column display:

                  $ ls -l /proc/self/map_files/
                  lr--------. 1 root root 64 Apr 16 21:31
                              3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so
                  ...

              Although these entries are present for memory regions that were
              mapped with  the MAP_FILE flag, the way anonymous shared memory
              (regions created with the MAP_ANON | MAP_SHARED flags) is
              implemented in Linux means that such regions also appear on this
              directory.  Here is an example where the target file is the
              deleted /dev/zero one:


                  lrw-------. 1 root root 64 Apr 16 21:33
                              7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)

              This directory appears only if the CONFIG_CHECKPOINT_RESTORE
              kernel configuration option is enabled.

       /proc/[pid]/maps
              A file containing the currently mapped memory regions and their
              access permissions.  See mmap(2) for some further information
              about memory mappings.

              The format of the file is:

       address           perms offset  dev   inode       pathname
       00400000-00452000 r-xp 00000000 08:02 173521      /usr/bin/dbus-daemon
       00651000-00652000 r--p 00051000 08:02 173521      /usr/bin/dbus-daemon
       00652000-00655000 rw-p 00052000 08:02 173521      /usr/bin/dbus-daemon
       00e03000-00e24000 rw-p 00000000 00:00 0           [heap]
       00e24000-011f7000 rw-p 00000000 00:00 0           [heap]
       ...
       35b1800000-35b1820000 r-xp 00000000 08:02 135522  /usr/lib64/ld-2.15.so
       35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522  /usr/lib64/ld-2.15.so
       35b1a20000-35b1a21000 rw-p 00020000 08:02 135522  /usr/lib64/ld-2.15.so
       35b1a21000-35b1a22000 rw-p 00000000 00:00 0
       35b1c00000-35b1dac000 r-xp 00000000 08:02 135870  /usr/lib64/libc-2.15.so
       35b1dac000-35b1fac000 ---p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so
       35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so
       35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870  /usr/lib64/libc-2.15.so
       ...
       f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0    [stack:986]
       ...
       7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0   [stack]
       7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0   [vdso]

              The address field is the address space in the process that the
              mapping occupies.  The perms field is a set of permissions:

                   r = read
                   w = write
                   x = execute
                   s = shared
                   p = private (copy on write)

              The offset field is the offset into the file/whatever; dev is
              the device (major:minor); inode is the inode on that device.  0
              indicates that no inode is associated with the memory region, as
              would be the case with BSS (uninitialized data).

              The pathname field will usually be the file that is backing the
              mapping.  For ELF files, you can easily coordinate with the
              offset field by looking at the Offset field in the ELF program
              headers (readelf -l).

              There are additional helpful pseudo-paths:

                   [stack]
                          The initial process's (also known as the main
                          thread's) stack.

                   [stack:<tid>] (since Linux 3.4)
                          A thread's stack (where the <tid> is a thread ID).
                          It corresponds to the /proc/[pid]/task/[tid]/ path.

                   [vdso] The virtual dynamically linked shared object.

                   [heap] The process's heap.

              If the pathname field is blank, this is an anonymous mapping as
              obtained via the mmap(2) function.  There is no easy way to
              coordinate this back to a process's source, short of running it
              through gdb(1), strace(1), or similar.

              Under Linux 2.0 there is no field giving pathname.

       /proc/[pid]/mem
              This file can be used to access the pages of a process's memory
              through open(2), read(2), and lseek(2).

       /proc/[pid]/mountinfo (since Linux 2.6.26)
              This file contains information about mount points.  It contains
              lines of the form:

              36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
              (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)

              The numbers in parentheses are labels for the descriptions
              below:

              (1)  mount ID: unique identifier of the mount (may be reused
                   after umount(2)).

              (2)  parent ID: ID of parent mount (or of self for the top of
                   the mount tree).

              (3)  major:minor: value of st_dev for files on file system (see
                   stat(2)).

              (4)  root: root of the mount within the file system.

              (5)  mount point: mount point relative to the process's root.

              (6)  mount options: per-mount options.

              (7)  optional fields: zero or more fields of the form
                   "tag[:value]".

              (8)  separator: marks the end of the optional fields.

              (9)  file system type: name of file system in the form
                   "type[.subtype]".

              (10) mount source: file system-specific information or "none".

              (11) super options: per-super block options.

              Parsers should ignore all unrecognized optional fields.
              Currently the possible optional fields are:

                   shared:X          mount is shared in peer group X

                   master:X          mount is slave to peer group X

                   propagate_from:X  mount is slave and receives propagation
                                     from peer group X (*)

                   unbindable        mount is unbindable

              (*) X is the closest dominant peer group under the process's
              root.  If X is the immediate master of the mount, or if there is
              no dominant peer group under the same root, then only the
              "master:X" field is present and not the "propagate_from:X"
              field.

              For more information on mount propagation see:
              Documentation/filesystems/sharedsubtree.txt in the Linux kernel
              source tree.

       /proc/[pid]/mounts (since Linux 2.4.19)
              This is a list of all the file systems currently mounted in the
              process's mount namespace.  The format of this file is
              documented in fstab(5).  Since kernel version 2.6.15, this file
              is pollable: after opening the file for reading, a change in
              this file (i.e., a file system mount or unmount) causes
              select(2) to mark the file descriptor as readable, and poll(2)
              and epoll_wait(2) mark the file as having an error condition.

       /proc/[pid]/mountstats (since Linux 2.6.17)
              This file exports information (statistics, configuration
              information) about the mount points in the process's name space.
              Lines in this file have the form:

              device /dev/sda7 mounted on /home with fstype ext3 [statistics]
              (       1      )            ( 2 )             (3 ) (4)

              The fields in each line are:

              (1)  The name of the mounted device (or "nodevice" if there is
                   no corresponding device).

              (2)  The mount point within the file system tree.

              (3)  The file system type.

              (4)  Optional statistics and configuration information.
                   Currently (as at Linux 2.6.26), only NFS file systems
                   export information via this field.

              This file is readable only by the owner of the process.

       /proc/[pid]/ns/ (since Linux 3.0)
              This is a subdirectory containing one entry for each namespace
              that supports being manipulated by setns(2).  For information
              about namespaces, see clone(2).

       /proc/[pid]/ns/ipc (since Linux 3.0)
              Bind mounting this file (see mount(2)) to somewhere else in the
              filesystem keeps the IPC namespace of the process specified by
              pid alive even if all processes currently in the namespace
              terminate.

              Opening this file returns a file handle for the IPC namespace of
              the process specified by pid.  As long as this file descriptor
              remains open, the IPC namespace will remain alive, even if all
              processes in the namespace terminate.  The file descriptor can
              be passed to setns(2).

       /proc/[pid]/ns/net (since Linux 3.0)
              Bind mounting this file (see mount(2)) to somewhere else in the
              filesystem keeps the network namespace of the process specified
              by pid alive even if all processes in the namespace terminate.

              Opening this file returns a file handle for the network
              namespace of the process specified by pid.  As long as this file
              descriptor remains open, the network namespace will remain
              alive, even if all processes in the namespace terminate.  The
              file descriptor can be passed to setns(2).

       /proc/[pid]/ns/uts (since Linux 3.0)
              Bind mounting this file (see mount(2)) to somewhere else in the
              filesystem keeps the UTS namespace of the process specified by
              pid alive even if all processes currently in the namespace
              terminate.

              Opening this file returns a file handle for the UTS namespace of
              the process specified by pid.  As long as this file descriptor
              remains open, the UTS namespace will remain alive, even if all
              processes in the namespace terminate.  The file descriptor can
              be passed to setns(2).

       /proc/[pid]/numa_maps (since Linux 2.6.14)
              See numa(7).

       /proc/[pid]/oom_adj (since Linux 2.6.11)
              This file can be used to adjust the score used to select which
              process should be killed in an out-of-memory (OOM) situation.
              The kernel uses this value for a bit-shift operation of the
              process's oom_score value: valid values are in the range -16 to
              +15, plus the special value -17, which disables OOM-killing
              altogether for this process.  A positive score increases the
              likelihood of this process being killed by the OOM-killer; a
              negative score decreases the likelihood.

              The default value for this file is 0; a new process inherits its
              parent's oom_adj setting.  A process must be privileged
              (CAP_SYS_RESOURCE) to update this file.

              Since Linux 2.6.36, use of this file is deprecated in favor of
              /proc/[pid]/oom_score_adj.

       /proc/[pid]/oom_score (since Linux 2.6.11)
              This file displays the current score that the kernel gives to
              this process for the purpose of selecting a process for the OOM-
              killer.  A higher score means that the process is more likely to
              be selected by the OOM-killer.  The basis for this score is the
              amount of memory used by the process, with increases (+) or
              decreases (-) for factors including:

              * whether the process creates a lot of children using fork(2)
                (+);

              * whether the process has been running a long time, or has used
                a lot of CPU time (-);

              * whether the process has a low nice value (i.e., > 0) (+);

              * whether the process is privileged (-); and

              * whether the process is making direct hardware access (-).

              The oom_score also reflects the adjustment specified by the
              oom_score_adj or oom_adj setting for the process.

       /proc/[pid]/oom_score_adj (since Linux 2.6.36)
              This file can be used to adjust the badness heuristic used to
              select which process gets killed in out-of-memory conditions.

              The badness heuristic assigns a value to each candidate task
              ranging from 0 (never kill) to 1000 (always kill) to determine
              which process is targeted.  The units are roughly a proportion
              along that range of allowed memory the process may allocate
              from, based on an estimation of its current memory and swap use.
              For example, if a task is using all allowed memory, its badness
              score will be 1000.  If it is using half of its allowed memory,
              its score will be 500.

              There is an additional factor included in the badness score:
              root processes are given 3% extra memory over other tasks.

              The amount of "allowed" memory depends on the context in which
              the OOM-killer was called.  If it is due to the memory assigned
              to the allocating task's cpuset being exhausted, the allowed
              memory represents the set of mems assigned to that cpuset (see
              cpuset(7)).  If it is due to a mempolicy's node(s) being
              exhausted, the allowed memory represents the set of mempolicy
              nodes.  If it is due to a memory limit (or swap limit) being
              reached, the allowed memory is that configured limit.  Finally,
              if it is due to the entire system being out of memory, the
              allowed memory represents all allocatable resources.

              The value of oom_score_adj is added to the badness score before
              it is used to determine which task to kill.  Acceptable values
              range from -1000 (OOM_SCORE_ADJ_MIN) to +1000
              (OOM_SCORE_ADJ_MAX).  This allows user space to control the
              preference for OOM-killing, ranging from always preferring a
              certain task or completely disabling it from OOM-killing.  The
              lowest possible value, -1000, is equivalent to disabling OOM-
              killing entirely for that task, since it will always report a
              badness score of 0.

              Consequently, it is very simple for user space to define the
              amount of memory to consider for each task.  Setting a
              oom_score_adj value of +500, for example, is roughly equivalent
              to allowing the remainder of tasks sharing the same system,
              cpuset, mempolicy, or memory controller resources to use at
              least 50% more memory.  A value of -500, on the other hand,
              would be roughly equivalent to discounting 50% of the task's
              allowed memory from being considered as scoring against the
              task.

              For backward compatibility with previous kernels,
              /proc/[pid]/oom_adj can still be used to tune the badness score.
              Its value is scaled linearly with oom_score_adj.

              Writing to /proc/[pid]/oom_score_adj or /proc/[pid]/oom_adj will
              change the other with its scaled value.

       /proc/[pid]/root
              UNIX and Linux support the idea of a per-process root of the
              file system, set by the chroot(2) system call.  This file is a
              symbolic link that points to the process's root directory, and
              behaves as exe, fd/*, etc. do.

              In a multithreaded process, the contents of this symbolic link
              are not available if the main thread has already terminated
              (typically by calling pthread_exit(3)).

       /proc/[pid]/smaps (since Linux 2.6.14)
              This file shows memory consumption for each of the process's
              mappings.  For each of mappings there is a series of lines such
              as the following:

                  00400000-0048a000 r-xp 00000000 fd:03 960637       /bin/bash
                  Size:                552 kB
                  Rss:                 460 kB
                  Pss:                 100 kB
                  Shared_Clean:        452 kB
                  Shared_Dirty:          0 kB
                  Private_Clean:         8 kB
                  Private_Dirty:         0 kB
                  Referenced:          460 kB
                  Anonymous:             0 kB
                  AnonHugePages:         0 kB
                  Swap:                  0 kB
                  KernelPageSize:        4 kB
                  MMUPageSize:           4 kB
                  KernelPageSize:        4 kB
                  MMUPageSize:           4 kB
                  Locked:                0 kB
                  VmFlags: rd ex mr mw me dw

              The first of these lines shows the same information as is
              displayed for the mapping in /proc/[pid]/maps.  The following
              lines show the size of the mapping, the amount of the mapping
              that is currently resident in RAM ("Rss"), the process's
              proportional share of this mapping ("Pss"), the number of clean
              and dirty shared pages in the mapping, and the number of clean
              and dirty private pages in the mapping.  "Referenced" indicates
              the amount of memory currently marked as referenced or accessed.
              "Anonymous" shows the amount of memory that does not belong to
              any file.  "Swap" shows how much would-be-anonymous memory is
              also used, but out on swap.

              The "KernelPageSize" line (available since Linux 2.6.29) is the
              page size used by the kernel to back the virtual memory area.
              This matches the size used by the MMU in the majority of cases.
              However, one counter-example occurs on PPC64 kernels whereby a
              kernel using 64kB as a base page size may still use 4kB pages
              for the MMU on older processors.  To distinguish the two
              attributes, the "MMUPageSize" line (also available since Linux
              2.6.29) reports the page size used by the MMU.

              The "Locked" indicates whether the mapping is locked in memory
              or not.

              The "VmFlags" line (available since Linux 3.8) represents the
              kernel flags associated with the virtual memory area, encoded
              using the following two-letter codes:

                  rd  - readable
                  wr  - writable
                  ex  - executable
                  sh  - shared
                  mr  - may read
                  mw  - may write
                  me  - may execute
                  ms  - may share
                  gd  - stack segment grows down
                  pf  - pure PFN range
                  dw  - disabled write to the mapped file
                  lo  - pages are locked in memory
                  io  - memory mapped I/O area
                  sr  - sequential read advise provided
                  rr  - random read advise provided
                  dc  - do not copy area on fork
                  de  - do not expand area on remapping
                  ac  - area is accountable
                  nr  - swap space is not reserved for the area
                  ht  - area uses huge tlb pages
                  nl  - non-linear mapping
                  ar  - architecture specific flag
                  dd  - do not include area into core dump
                  sd  - soft-dirty flag
                  mm  - mixed map area
                  hg  - huge page advise flag
                  nh  - no-huge page advise flag
                  mg  - mergeable advise flag

              The /proc/[pid]/smaps file is present only if the
              CONFIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/[pid]/stat
              Status information about the process.  This is used by ps(1).
              It is defined in /usr/src/linux/fs/proc/array.c.

              The fields, in order, with their proper scanf(3) format
              specifiers, are:

              pid %d      (1) The process ID.

              comm %s     (2) The filename of the executable, in parentheses.
                          This is visible whether or not the executable is
                          swapped out.

              state %c    (3) One character from the string "RSDZTW" where R
                          is running, S is sleeping in an interruptible wait,
                          D is waiting in uninterruptible disk sleep, Z is
                          zombie, T is traced or stopped (on a signal), and W
                          is paging.

              ppid %d     (4) The PID of the parent.

              pgrp %d     (5) The process group ID of the process.

              session %d  (6) The session ID of the process.

              tty_nr %d   (7) The controlling terminal of the process.  (The
                          minor device number is contained in the combination
                          of bits 31 to 20 and 7 to 0; the major device number
                          is in bits 15 to 8.)

              tpgid %d    (8) The ID of the foreground process group of the
                          controlling terminal of the process.

              flags %u (%lu before Linux 2.6.22)
                          (9) The kernel flags word of the process.  For bit
                          meanings, see the PF_* defines in the Linux kernel
                          source file include/linux/sched.h.  Details depend
                          on the kernel version.

              minflt %lu  (10) The number of minor faults the process has made
                          which have not required loading a memory page from
                          disk.

              cminflt %lu (11) The number of minor faults that the process's
                          waited-for children have made.

              majflt %lu  (12) The number of major faults the process has made
                          which have required loading a memory page from disk.

              cmajflt %lu (13) The number of major faults that the process's
                          waited-for children have made.

              utime %lu   (14) Amount of time that this process has been
                          scheduled in user mode, measured in clock ticks
                          (divide by sysconf(_SC_CLK_TCK)).  This includes
                          guest time, guest_time (time spent running a virtual
                          CPU, see below), so that applications that are not
                          aware of the guest time field do not lose that time
                          from their calculations.

              stime %lu   (15) Amount of time that this process has been
                          scheduled in kernel mode, measured in clock ticks
                          (divide by sysconf(_SC_CLK_TCK)).

              cutime %ld  (16) Amount of time that this process's waited-for
                          children have been scheduled in user mode, measured
                          in clock ticks (divide by sysconf(_SC_CLK_TCK)).
                          (See also times(2).)  This includes guest time,
                          cguest_time (time spent running a virtual CPU, see
                          below).

              cstime %ld  (17) Amount of time that this process's waited-for
                          children have been scheduled in kernel mode,
                          measured in clock ticks (divide by
                          sysconf(_SC_CLK_TCK)).

              priority %ld
                          (18) (Explanation for Linux 2.6) For processes
                          running a real-time scheduling policy (policy below;
                          see sched_setscheduler(2)), this is the negated
                          scheduling priority, minus one; that is, a number in
                          the range -2 to -100, corresponding to real-time
                          priorities 1 to 99.  For processes running under a
                          non-real-time scheduling policy, this is the raw
                          nice value (setpriority(2)) as represented in the
                          kernel.  The kernel stores nice values as numbers in
                          the range 0 (high) to 39 (low), corresponding to the
                          user-visible nice range of -20 to 19.

                          Before Linux 2.6, this was a scaled value based on
                          the scheduler weighting given to this process.

              nice %ld    (19) The nice value (see setpriority(2)), a value in
                          the range 19 (low priority) to -20 (high priority).

              num_threads %ld
                          (20) Number of threads in this process (since Linux
                          2.6).  Before kernel 2.6, this field was hard coded
                          to 0 as a placeholder for an earlier removed field.

              itrealvalue %ld
                          (21) The time in jiffies before the next SIGALRM is
                          sent to the process due to an interval timer.  Since
                          kernel 2.6.17, this field is no longer maintained,
                          and is hard coded as 0.

              starttime %llu (was %lu before Linux 2.6)
                          (22) The time the process started after system boot.
                          In kernels before Linux 2.6, this value was
                          expressed in jiffies.  Since Linux 2.6, the value is
                          expressed in clock ticks (divide by
                          sysconf(_SC_CLK_TCK)).

              vsize %lu   (23) Virtual memory size in bytes.

              rss %ld     (24) Resident Set Size: number of pages the process
                          has in real memory.  This is just the pages which
                          count toward text, data, or stack space.  This does
                          not include pages which have not been demand-loaded
                          in, or which are swapped out.

              rsslim %lu  (25) Current soft limit in bytes on the rss of the
                          process; see the description of RLIMIT_RSS in
                          getrlimit(2).

              startcode %lu
                          (26) The address above which program text can run.

              endcode %lu (27) The address below which program text can run.

              startstack %lu
                          (28) The address of the start (i.e., bottom) of the
                          stack.

              kstkesp %lu (29) The current value of ESP (stack pointer), as
                          found in the kernel stack page for the process.

              kstkeip %lu (30) The current EIP (instruction pointer).

              signal %lu  (31) The bitmap of pending signals, displayed as a
                          decimal number.  Obsolete, because it does not
                          provide information on real-time signals; use
                          /proc/[pid]/status instead.

              blocked %lu (32) The bitmap of blocked signals, displayed as a
                          decimal number.  Obsolete, because it does not
                          provide information on real-time signals; use
                          /proc/[pid]/status instead.

              sigignore %lu
                          (33) The bitmap of ignored signals, displayed as a
                          decimal number.  Obsolete, because it does not
                          provide information on real-time signals; use
                          /proc/[pid]/status instead.

              sigcatch %lu
                          (34) The bitmap of caught signals, displayed as a
                          decimal number.  Obsolete, because it does not
                          provide information on real-time signals; use
                          /proc/[pid]/status instead.

              wchan %lu   (35) This is the "channel" in which the process is
                          waiting.  It is the address of a system call, and
                          can be looked up in a namelist if you need a textual
                          name.  (If you have an up-to-date /etc/psdatabase,
                          then try ps -l to see the WCHAN field in action.)

              nswap %lu   (36) Number of pages swapped (not maintained).

              cnswap %lu  (37) Cumulative nswap for child processes (not
                          maintained).

              exit_signal %d (since Linux 2.1.22)
                          (38) Signal to be sent to parent when we die.

              processor %d (since Linux 2.2.8)
                          (39) CPU number last executed on.

              rt_priority %u (since Linux 2.5.19; was %lu before Linux 2.6.22)
                          (40) Real-time scheduling priority, a number in the
                          range 1 to 99 for processes scheduled under a real-
                          time policy, or 0, for non-real-time processes (see
                          sched_setscheduler(2)).

              policy %u (since Linux 2.5.19; was %lu before Linux 2.6.22)
                          (41) Scheduling policy (see sched_setscheduler(2)).
                          Decode using the SCHED_* constants in linux/sched.h.

              delayacct_blkio_ticks %llu (since Linux 2.6.18)
                          (42) Aggregated block I/O delays, measured in clock
                          ticks (centiseconds).

              guest_time %lu (since Linux 2.6.24)
                          (43) Guest time of the process (time spent running a
                          virtual CPU for a guest operating system), measured
                          in clock ticks (divide by sysconf(_SC_CLK_TCK)).

              cguest_time %ld (since Linux 2.6.24)
                          (44) Guest time of the process's children, measured
                          in clock ticks (divide by sysconf(_SC_CLK_TCK)).

              start_data %lu (since Linux 3.3)
                          (45) Address above which program data+bss is placed.

              end_data %lu (since Linux 3.3)
                          (46) Address below which program data+bss is placed.

              start_brk %lu (since Linux 3.3)
                          (47) Address above which program heap can be
                          expanded with brk().

              arg_start %lu (since Linux 3.5)
                          (48) Address above which program command line is
                          placed.

              arg_end %lu (since Linux 3.5)
                          (49) Address below which program command line is
                          placed.

              env_start %lu (since Linux 3.5)
                          (50) Address above which program environment is
                          placed.

              env_end %lu (since Linux 3.5)
                          (51) Address below which program environment is
                          placed.

              exit_code %d (since Linux 3.5)
                          (52) The thread's exit_code in the form reported by
                          the waitpid system.

       /proc/[pid]/statm
              Provides information about memory usage, measured in pages.  The
              columns are:

                  size       (1) total program size
                             (same as VmSize in /proc/[pid]/status)
                  resident   (2) resident set size
                             (same as VmRSS in /proc/[pid]/status)
                  share      (3) shared pages (i.e., backed by a file)
                  text       (4) text (code)
                  lib        (5) library (unused in Linux 2.6)
                  data       (6) data + stack
                  dt         (7) dirty pages (unused in Linux 2.6)

       /proc/[pid]/status
              Provides much of the information in /proc/[pid]/stat and
              /proc/[pid]/statm in a format that's easier for humans to parse.
              Here's an example:

                  $ cat /proc/$$/status
                  Name:   bash
                  Umask:  0022
                  State:  S (sleeping)
                  Tgid:   17248
                  Ngid:   0
                  Pid:    17248
                  PPid:   17200
                  TracerPid:      0
                  Uid:    1000    1000    1000    1000
                  Gid:    100     100     100     100
                  FDSize: 256
                  Groups: 16 33 100
                  VmPeak:   131168 kB
                  VmSize:   131168 kB
                  VmLck:         0 kB
                  VmPin:         0 kB
                  VmHWM:     13484 kB
                  VmRSS:     13484 kB
                  RssAnon:       10264 kB
                  RssFile:        3220 kB
                  RssShmem:          0 kB
                  VmData:    10332 kB
                  VmStk:       136 kB
                  VmExe:       992 kB
                  VmLib:      2104 kB
                  VmPTE:        76 kB
                  Threads:        1
                  SigQ:   0/3067
                  SigPnd: 0000000000000000
                  ShdPnd: 0000000000000000
                  SigBlk: 0000000000010000
                  SigIgn: 0000000000384004
                  SigCgt: 000000004b813efb
                  CapInh: 0000000000000000
                  CapPrm: 0000000000000000
                  CapEff: 0000000000000000
                  CapBnd: ffffffffffffffff
                  CapAmb: 0000000000000000
                  Seccomp:        0
                  Speculation_Store_Bypass:       vulnerable
                  Cpus_allowed:   00000001
                  Cpus_allowed_list:      0
                  Mems_allowed:   1
                  Mems_allowed_list:      0
                  voluntary_ctxt_switches:        150
                  nonvoluntary_ctxt_switches:     545

              The fields are as follows:

              * Name: Command run by this process.

              * Umask: Process umask, expressed in octal with a leading zero;
                see umask(2).  (Since Linux 4.7.)

              * State: Current state of the process.  One of "R (running)", "S
                (sleeping)", "D (disk sleep)", "T (stopped)", "T (tracing
                stop)", "Z (zombie)", or "X (dead)".

              * Tgid: Thread group ID (i.e., Process ID).

              * Ngid: NUMA group ID (0 if none; since Linux 3.13).

              * Pid: Thread ID (see gettid(2)).

              * PPid: PID of parent process.

              * TracerPid: PID of process tracing this process (0 if not being
                traced).

              * Uid, Gid: Real, effective, saved set, and filesystem UIDs
                (GIDs).

              * FDSize: Number of file descriptor slots currently allocated.

              * Groups: Supplementary group list.

              * VmPeak: Peak virtual memory size.

              * VmSize: Virtual memory size.

              * VmLck: Locked memory size (see mlock(2)).

              * VmPin: Pinned memory size (since Linux 3.2).  These are pages
                that can't be moved because something needs to directly access
                physical memory.

              * VmHWM: Peak resident set size ("high water mark").

              * VmRSS: Resident set size.  Note that the value here is the sum
                of RssAnon, RssFile, and RssShmem.

              * RssAnon: Size of resident anonymous memory.  (since Linux
                4.5).

              * RssFile: Size of resident file mappings.  (since Linux 4.5).

              * RssShmem: Size of resident shared memory (includes System V
                shared memory, mappings from tmpfs(5), and shared anonymous
                mappings).  (since Linux 4.5).

              * VmData, VmStk, VmExe: Size of data, stack, and text segments.

              * VmLib: Shared library code size.

              * VmPTE: Page table entries size (since Linux 2.6.10).

              * Threads: Number of threads in process containing this thread.

              * SigQ: This field contains two slash-separated numbers that
                relate to queued signals for the real user ID of this process.
                The first of these is the number of currently queued signals
                for this real user ID, and the second is the resource limit on
                the number of queued signals for this process (see the
                description of RLIMIT_SIGPENDING in getrlimit(2)).

              * SigPnd, ShdPnd: Number of signals pending for thread and for
                process as a whole (see pthreads(7) and signal(7)).

              * SigBlk, SigIgn, SigCgt: Masks indicating signals being
                blocked, ignored, and caught (see signal(7)).

              * CapInh, CapPrm, CapEff: Masks of capabilities enabled in
                inheritable, permitted, and effective sets (see
                capabilities(7)).

              * CapBnd: Capability Bounding set (since Linux 2.6.26, see
                capabilities(7)).

              * CapAmb: Ambient capability set (since Linux 4.3, see
                capabilities(7)).

              * Seccomp: Seccomp mode of the process (since Linux 3.8, see
                seccomp(2)).  0 means SECCOMP_MODE_DISABLED; 1 means
                SECCOMP_MODE_STRICT; 2 means SECCOMP_MODE_FILTER.  This field
                is provided only if the kernel was built with the
                CONFIG_SECCOMP kernel configuration option enabled.

              * Speculation_Store_Bypass: Speculation flaw mitigation state
                (since Linux 4.17, see prctl(2)).

              * Cpus_allowed: Mask of CPUs on which this process may run
                (since Linux 2.6.24, see cpuset(7)).

              * Cpus_allowed_list: Same as previous, but in "list format"
                (since Linux 2.6.26, see cpuset(7)).

              * Mems_allowed: Mask of memory nodes allowed to this process
                (since Linux 2.6.24, see cpuset(7)).

              * Mems_allowed_list: Same as previous, but in "list format"
                (since Linux 2.6.26, see cpuset(7)).

              * voluntary_ctxt_switches, nonvoluntary_ctxt_switches: Number of
                voluntary and involuntary context switches (since Linux
                2.6.23).

       /proc/[pid]/task (since Linux 2.6.0-test6)
              This is a directory that contains one subdirectory for each
              thread in the process.  The name of each subdirectory is the
              numerical thread ID ([tid]) of the thread (see gettid(2)).
              Within each of these subdirectories, there is a set of files
              with the same names and contents as under the /proc/[pid]
              directories.  For attributes that are shared by all threads, the
              contents for each of the files under the task/[tid]
              subdirectories will be the same as in the corresponding file in
              the parent /proc/[pid] directory (e.g., in a multithreaded
              process, all of the task/[tid]/cwd files will have the same
              value as the /proc/[pid]/cwd file in the parent directory, since
              all of the threads in a process share a working directory).  For
              attributes that are distinct for each thread, the corresponding
              files under task/[tid] may have different values (e.g., various
              fields in each of the task/[tid]/status files may be different
              for each thread).

              In a multithreaded process, the contents of the /proc/[pid]/task
              directory are not available if the main thread has already
              terminated (typically by calling pthread_exit(3)).

       /proc/apm
              Advanced power management version and battery information when
              CONFIG_APM is defined at kernel compilation time.

       /proc/bus
              Contains subdirectories for installed busses.

       /proc/bus/pccard
              Subdirectory for PCMCIA devices when CONFIG_PCMCIA is set at
              kernel compilation time.

       /proc/bus/pccard/drivers

       /proc/bus/pci
              Contains various bus subdirectories and pseudo-files containing
              information about PCI busses, installed devices, and device
              drivers.  Some of these files are not ASCII.

       /proc/bus/pci/devices
              Information about PCI devices.  They may be accessed through
              lspci(8) and setpci(8).

       /proc/cmdline
              Arguments passed to the Linux kernel at boot time.  Often done
              via a boot manager such as lilo(8) or grub(8).

       /proc/config.gz (since Linux 2.6)
              This file exposes the configuration options that were used to
              build the currently running kernel, in the same format as they
              would be shown in the .config file that resulted when
              configuring the kernel (using make xconfig, make config, or
              similar).  The file contents are compressed; view or search them
              using zcat(1), zgrep(1), etc.  As long as no changes have been
              made to the following file, the contents of /proc/config.gz are
              the same as those provided by :

                  cat /lib/modules/$(uname -r)/build/.config

              /proc/config.gz is provided only if the kernel is configured
              with CONFIG_IKCONFIG_PROC.

       /proc/cpuinfo
              This is a collection of CPU and system architecture dependent
              items, for each supported architecture a different list.  Two
              common entries are processor which gives CPU number and
              bogomips; a system constant that is calculated during kernel
              initialization.  SMP machines have information for each CPU.
              The lscpu(1) command gathers its information from this file.

       /proc/devices
              Text listing of major numbers and device groups.  This can be
              used by MAKEDEV scripts for consistency with the kernel.

       /proc/diskstats (since Linux 2.5.69)
              This file contains disk I/O statistics for each disk device.
              See the Linux kernel source file Documentation/iostats.txt for
              further information.

       /proc/dma
              This is a list of the registered ISA DMA (direct memory access)
              channels in use.

       /proc/driver
              Empty subdirectory.

       /proc/execdomains
              List of the execution domains (ABI personalities).

       /proc/fb
              Frame buffer information when CONFIG_FB is defined during kernel
              compilation.

       /proc/filesystems
              A text listing of the file systems which are supported by the
              kernel, namely file systems which were compiled into the kernel
              or whose kernel modules are currently loaded.  (See also
              filesystems(5).)  If a file system is marked with "nodev", this
              means that it does not require a block device to be mounted
              (e.g., virtual file system, network file system).

              Incidentally, this file may be used by mount(8) when no file
              system is specified and it didn't manage to determine the file
              system type.  Then file systems contained in this file are tried
              (excepted those that are marked with "nodev").

       /proc/fs
              Contains subdirectories that in turn contain files with
              information about (certain) mounted filesystems.

       /proc/ide
              This directory exists on systems with the IDE bus.  There are
              directories for each IDE channel and attached device.  Files
              include:

                  cache              buffer size in KB
                  capacity           number of sectors
                  driver             driver version
                  geometry           physical and logical geometry
                  identify           in hexadecimal
                  media              media type
                  model              manufacturer's model number
                  settings           drive settings
                  smart_thresholds   in hexadecimal
                  smart_values       in hexadecimal

              The hdparm(8) utility provides access to this information in a
              friendly format.

       /proc/interrupts
              This is used to record the number of interrupts per CPU per IO
              device.  Since Linux 2.6.24, for the i386 and x86_64
              architectures, at least, this also includes interrupts internal
              to the system (that is, not associated with a device as such),
              such as NMI (nonmaskable interrupt), LOC (local timer
              interrupt), and for SMP systems, TLB (TLB flush interrupt), RES
              (rescheduling interrupt), CAL (remote function call interrupt),
              and possibly others.  Very easy to read formatting, done in
              ASCII.

       /proc/iomem
              I/O memory map in Linux 2.4.

       /proc/ioports
              This is a list of currently registered Input-Output port regions
              that are in use.

       /proc/kallsyms (since Linux 2.5.71)
              This holds the kernel exported symbol definitions used by the
              modules(X) tools to dynamically link and bind loadable modules.
              In Linux 2.5.47 and earlier, a similar file with slightly
              different syntax was named ksyms.

       /proc/kcore
              This file represents the physical memory of the system and is
              stored in the ELF core file format.  With this pseudo-file, and
              an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be
              used to examine the current state of any kernel data structures.

              The total length of the file is the size of physical memory
              (RAM) plus 4KB.

       /proc/kmsg
              This file can be used instead of the syslog(2) system call to
              read kernel messages.  A process must have superuser privileges
              to read this file, and only one process should read this file.
              This file should not be read if a syslog process is running
              which uses the syslog(2) system call facility to log kernel
              messages.

              Information in this file is retrieved with the dmesg(1) program.

       /proc/ksyms (Linux 1.1.23-2.5.47)
              See /proc/kallsyms.

       /proc/loadavg
              The first three fields in this file are load average figures
              giving the number of jobs in the run queue (state R) or waiting
              for disk I/O (state D) averaged over 1, 5, and 15 minutes.  They
              are the same as the load average numbers given by uptime(1) and
              other programs.  The fourth field consists of two numbers
              separated by a slash (/).  The first of these is the number of
              currently runnable kernel scheduling entities (processes,
              threads).  The value after the slash is the number of kernel
              scheduling entities that currently exist on the system.  The
              fifth field is the PID of the process that was most recently
              created on the system.

       /proc/locks
              This file shows current file locks (flock(2) and fcntl(2)) and
              leases (fcntl(2)).

       /proc/malloc (only up to and including Linux 2.2)
              This file is present only if CONFIG_DEBUG_MALLOC was defined
              during compilation.

       /proc/meminfo
              This file reports statistics about memory usage on the system.
              It is used by free(1) to report the amount of free and used
              memory (both physical and swap) on the system as well as the
              shared memory and buffers used by the kernel.  Each line of the
              file consists of a parameter name, followed by a colon, the
              value of the parameter, and an option unit of measurement (e.g.,
              "kB").  The list below describes the parameter names and the
              format specifier required to read the field value.  Except as
              noted below, all of the fields have been present since at least
              Linux 2.6.0.  Some fileds are displayed only if the kernel was
              configured with various options; those dependencies are noted in
              the list.

              MemTotal %lu
                     Total usable RAM (i.e. physical RAM minus a few reserved
                     bits and the kernel binary code).

              MemFree %lu
                     The sum of LowFree+HighFree.

              Buffers %lu
                     Relatively temporary storage for raw disk blocks that
                     shouldn't get tremendously large (20MB or so).

              Cached %lu
                     In-memory cache for files read from the disk (the page
                     cache).  Doesn't include SwapCached.

              SwapCached %lu
                     Memory that once was swapped out, is swapped back in but
                     still also is in the swap file.  (If memory pressure is
                     high, these pages don't need to be swapped out again
                     because they are already in the swap file.  This saves
                     I/O.)

              Active %lu
                     Memory that has been used more recently and usually not
                     reclaimed unless absolutely necessary.

              Inactive %lu
                     Memory which has been less recently used.  It is more
                     eligible to be reclaimed for other purposes.

              Active(anon) %lu (since Linux 2.6.28)
                     [To be documented.]

              Inactive(anon) %lu (since Linux 2.6.28)
                     [To be documented.]

              Active(file) %lu (since Linux 2.6.28)
                     [To be documented.]

              Inactive(file) %lu (since Linux 2.6.28)
                     [To be documented.]

              Unevictable %lu (since Linux 2.6.28)
                     (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was
                     required.)  [To be documented.]

              Mlocked %lu (since Linux 2.6.28)
                     (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was
                     required.)  [To be documented.]

              HighTotal %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Total amount of highmem.  Highmem is all memory above
                     ~860MB of physical memory.  Highmem areas are for use by
                     user-space programs, or for the page cache.  The kernel
                     must use tricks to access this memory, making it slower
                     to access than lowmem.

              HighFree %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Amount of free highmem.

              LowTotal %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Total amount of lowmem.  Lowmem is memory which can be
                     used for everything that highmem can be used for, but it
                     is also available for the kernel's use for its own data
                     structures.  Among many other things, it is where
                     everything from Slab is allocated.  Bad things happen
                     when you're out of lowmem.

              LowFree %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Amount of free lowmem.

              MmapCopy %lu (since Linux 2.6.29)
                     (CONFIG_MMU is required.)  [To be documented.]

              SwapTotal %lu
                     Total amount of swap space available.

              SwapFree %lu
                     Amount of swap space that is currently unused.

              Dirty %lu
                     Memory which is waiting to get written back to the disk.

              Writeback %lu
                     Memory which is actively being written back to the disk.

              AnonPages %lu (since Linux 2.6.18)
                     Non-file backed pages mapped into user-space page tables.

              Mapped %lu
                     Files which have been mmaped, such as libraries.

              Shmem %lu (since Linux 2.6.32)
                     [To be documented.]

              Slab %lu
                     In-kernel data structures cache.

              SReclaimable %lu (since Linux 2.6.19)
                     Part of Slab, that might be reclaimed, such as caches.

              SUnreclaim %lu (since Linux 2.6.19)
                     Part of Slab, that cannot be reclaimed on memory
                     pressure.

              KernelStack %lu (since Linux 2.6.32)
                     Amount of memory allocated to kernel stacks.

              PageTables %lu (since Linux 2.6.18)
                     Amount of memory dedicated to the lowest level of page
                     tables.

              Quicklists %lu (since Linux 2.6.27)
                     (CONFIG_QUICKLIST is required.)  [To be documented.]

              NFS_Unstable %lu (since Linux 2.6.18)
                     NFS pages sent to the server, but not yet committed to
                     stable storage.

              Bounce %lu (since Linux 2.6.18)
                     Memory used for block device "bounce buffers".

              WritebackTmp %lu (since Linux 2.6.26)
                     Memory used by FUSE for temporary writeback buffers.

              CommitLimit %lu (since Linux 2.6.10)
                     Based on the overcommit ratio ('vm.overcommit_ratio'),
                     this is the total amount of  memory currently available
                     to be allocated on the system.  This limit is adhered to
                     only if strict overcommit accounting is enabled (mode 2
                     in /proc/sys/vm/overcommit_ratio).  The CommitLimit is
                     calculated using the following formula:

                         CommitLimit = (overcommit_ratio * Physical RAM) +
                     Swap

                     For example, on a system with 1GB of physical RAM and 7GB
                     of swap with a overcommit_ratio of 30, this formula
                     yields a CommitLimit of 7.3GB.  For more details, see the
                     memory overcommit documentation in the kernel source file
                     Documentation/vm/overcommit-accounting.

              Committed_AS %lu
                     The amount of memory presently allocated on the system.
                     The committed memory is a sum of all of the memory which
                     has been allocated by processes, even if it has not been
                     "used" by them as of yet.  A process which allocates 1GB
                     of memory (using malloc(3) or similar), but touches only
                     300MB of that memory will show up as using only 300MB of
                     memory even if it has the address space allocated for the
                     entire 1GB.  This 1GB is memory which has been
                     "committed" to by the VM and can be used at any time by
                     the allocating application.  With strict overcommit
                     enabled on the system (mode 2
                     /proc/sys/vm/overcommit_memory), allocations which would
                     exceed the CommitLimit (detailed above) will not be
                     permitted.  This is useful if one needs to guarantee that
                     processes will not fail due to lack of memory once that
                     memory has been successfully allocated.

              VmallocTotal %lu
                     Total size of vmalloc memory area.

              VmallocUsed %lu
                     Amount of vmalloc area which is used.

              VmallocChunk %lu
                     Largest contiguous block of vmalloc area which is free.

              HardwareCorrupted %lu (since Linux 2.6.32)
                     (CONFIG_MEMORY_FAILURE is required.)  [To be documented.]

              AnonHugePages %lu (since Linux 2.6.38)
                     (CONFIG_TRANSPARENT_HUGEPAGE is required.)  Non-file
                     backed huge pages mapped into user-space page tables.

              HugePages_Total %lu
                     (CONFIG_HUGETLB_PAGE is required.)  The size of the pool
                     of huge pages.

              HugePages_Free %lu
                     (CONFIG_HUGETLB_PAGE is required.)  The number of huge
                     pages in the pool that are not yet allocated.

              HugePages_Rsvd %lu (since Linux 2.6.17)
                     (CONFIG_HUGETLB_PAGE is required.)  This is the number of
                     huge pages for which a commitment to allocate from the
                     pool has been made, but no allocation has yet been made.
                     These reserved huge pages guarantee that an application
                     will be able to allocate a huge page from the pool of
                     huge pages at fault time.

              HugePages_Surp %lu (since Linux 2.6.24)
                     (CONFIG_HUGETLB_PAGE is required.)  This is the number of
                     huge pages in the pool above the value in
                     /proc/sys/vm/nr_hugepages.  The maximum number of surplus
                     huge pages is controlled by
                     /proc/sys/vm/nr_overcommit_hugepages.

              Hugepagesize %lu
                     (CONFIG_HUGETLB_PAGE is required.)  The size of huge
                     pages.

       /proc/modules
              A text list of the modules that have been loaded by the system.
              See also lsmod(8).

       /proc/mounts
              Before kernel 2.4.19, this file was a list of all the file
              systems currently mounted on the system.  With the introduction
              of per-process mount namespaces in Linux 2.4.19, this file
              became a link to /proc/self/mounts, which lists the mount points
              of the process's own mount namespace.  The format of this file
              is documented in fstab(5).

       /proc/mtrr
              Memory Type Range Registers.  See the Linux kernel source file
              Documentation/mtrr.txt for details.

       /proc/net
              various net pseudo-files, all of which give the status of some
              part of the networking layer.  These files contain ASCII
              structures and are, therefore, readable with cat(1).  However,
              the standard netstat(8) suite provides much cleaner access to
              these files.

       /proc/net/arp
              This holds an ASCII readable dump of the kernel ARP table used
              for address resolutions.  It will show both dynamically learned
              and preprogrammed ARP entries.  The format is:

        IP address     HW type   Flags     HW address          Mask   Device
        192.168.0.50   0x1       0x2       00:50:BF:25:68:F3   *      eth0
        192.168.0.250  0x1       0xc       00:00:00:00:00:00   *      eth0

              Here "IP address" is the IPv4 address of the machine and the "HW
              type" is the hardware type of the address from RFC 826.  The
              flags are the internal flags of the ARP structure (as defined in
              /usr/include/linux/if_arp.h) and the "HW address" is the data
              link layer mapping for that IP address if it is known.

       /proc/net/dev
              The dev pseudo-file contains network device status information.
              This gives the number of received and sent packets, the number
              of errors and collisions and other basic statistics.  These are
              used by the ifconfig(8) program to report device status.  The
              format is:

 Inter-|   Receive                                                |  Transmit
  face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
     lo: 2776770   11307    0    0    0     0          0         0  2776770   11307    0    0    0     0       0          0
   eth0: 1215645    2751    0    0    0     0          0         0  1782404    4324    0    0    0   427       0          0
   ppp0: 1622270    5552    1    0    0     0          0         0   354130    5669    0    0    0     0       0          0
   tap0:    7714      81    0    0    0     0          0         0     7714      81    0    0    0     0       0          0

       /proc/net/dev_mcast
              Defined in /usr/src/linux/net/core/dev_mcast.c:
                   indx interface_name  dmi_u dmi_g dmi_address
                   2    eth0            1     0     01005e000001
                   3    eth1            1     0     01005e000001
                   4    eth2            1     0     01005e000001

       /proc/net/igmp
              Internet Group Management Protocol.  Defined in
              /usr/src/linux/net/core/igmp.c.

       /proc/net/rarp
              This file uses the same format as the arp file and contains the
              current reverse mapping database used to provide rarp(8) reverse
              address lookup services.  If RARP is not configured into the
              kernel, this file will not be present.

       /proc/net/raw
              Holds a dump of the RAW socket table.  Much of the information
              is not of use apart from debugging.  The "sl" value is the
              kernel hash slot for the socket, the "local_address" is the
              local address and protocol number pair.  "St" is the internal
              status of the socket.  The "tx_queue" and "rx_queue" are the
              outgoing and incoming data queue in terms of kernel memory
              usage.  The "tr", "tm->when", and "rexmits" fields are not used
              by RAW.  The "uid" field holds the effective UID of the creator
              of the socket.

       /proc/net/snmp
              This file holds the ASCII data needed for the IP, ICMP, TCP, and
              UDP management information bases for an SNMP agent.

       /proc/net/tcp
              Holds a dump of the TCP socket table.  Much of the information
              is not of use apart from debugging.  The "sl" value is the
              kernel hash slot for the socket, the "local_address" is the
              local address and port number pair.  The "rem_address" is the
              remote address and port number pair (if connected).  "St" is the
              internal status of the socket.  The "tx_queue" and "rx_queue"
              are the outgoing and incoming data queue in terms of kernel
              memory usage.  The "tr", "tm->when", and "rexmits" fields hold
              internal information of the kernel socket state and are only
              useful for debugging.  The "uid" field holds the effective UID
              of the creator of the socket.

       /proc/net/udp
              Holds a dump of the UDP socket table.  Much of the information
              is not of use apart from debugging.  The "sl" value is the
              kernel hash slot for the socket, the "local_address" is the
              local address and port number pair.  The "rem_address" is the
              remote address and port number pair (if connected). "St" is the
              internal status of the socket.  The "tx_queue" and "rx_queue"
              are the outgoing and incoming data queue in terms of kernel
              memory usage.  The "tr", "tm->when", and "rexmits" fields are
              not used by UDP.  The "uid" field holds the effective UID of the
              creator of the socket.  The format is:

 sl  local_address rem_address   st tx_queue rx_queue tr rexmits  tm->when uid
  1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
  1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
  1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0

       /proc/net/unix
              Lists the UNIX domain sockets present within the system and
              their status.  The format is:
              Num RefCount Protocol Flags    Type St Path
               0: 00000002 00000000 00000000 0001 03
               1: 00000001 00000000 00010000 0001 01 /dev/printer

              Here "Num" is the kernel table slot number, "RefCount" is the
              number of users of the socket, "Protocol" is currently always 0,
              "Flags" represent the internal kernel flags holding the status
              of the socket.  Currently, type is always "1" (UNIX domain
              datagram sockets are not yet supported in the kernel).  "St" is
              the internal state of the socket and Path is the bound path (if
              any) of the socket.

       /proc/partitions
              Contains major and minor numbers of each partition as well as
              number of blocks and partition name.

       /proc/pci
              This is a listing of all PCI devices found during kernel
              initialization and their configuration.

              This file has been deprecated in favor of a new /proc interface
              for PCI (/proc/bus/pci).  It became optional in Linux 2.2
              (available with CONFIG_PCI_OLD_PROC set at kernel compilation).
              It became once more nonoptionally enabled in Linux 2.4.  Next,
              it was deprecated in Linux 2.6 (still available with
              CONFIG_PCI_LEGACY_PROC set), and finally removed altogether
              since Linux 2.6.17.

       /proc/profile (since Linux 2.4)
              This file is present only if the kernel was booted with the
              profile=1 command-line option.  It exposes kernel profiling
              information in a binary format for use by readprofile(1).
              Writing (e.g., an empty string) to this file resets the
              profiling counters; on some architectures, writing a binary
              integer "profiling multiplier" of size sizeof(int) sets the
              profiling interrupt frequency.

       /proc/scsi
              A directory with the scsi mid-level pseudo-file and various SCSI
              low-level driver directories, which contain a file for each SCSI
              host in this system, all of which give the status of some part
              of the SCSI IO subsystem.  These files contain ASCII structures
              and are, therefore, readable with cat(1).

              You can also write to some of the files to reconfigure the
              subsystem or switch certain features on or off.

       /proc/scsi/scsi
              This is a listing of all SCSI devices known to the kernel.  The
              listing is similar to the one seen during bootup.  scsi
              currently supports only the add-single-device command which
              allows root to add a hotplugged device to the list of known
              devices.

              The command

                  echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi

              will cause host scsi1 to scan on SCSI channel 0 for a device on
              ID 5 LUN 0.  If there is already a device known on this address
              or the address is invalid, an error will be returned.

       /proc/scsi/[drivername]
              [drivername] can currently be NCR53c7xx, aha152x, aha1542,
              aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000,
              pas16, qlogic, scsi_debug, seagate, t128, u15-24f, ultrastore,
              or wd7000.  These directories show up for all drivers that
              registered at least one SCSI HBA.  Every directory contains one
              file per registered host.  Every host-file is named after the
              number the host was assigned during initialization.

              Reading these files will usually show driver and host
              configuration, statistics, etc.

              Writing to these files allows different things on different
              hosts.  For example, with the latency and nolatency commands,
              root can switch on and off command latency measurement code in
              the eata_dma driver.  With the lockup and unlock commands, root
              can control bus lockups simulated by the scsi_debug driver.

       /proc/self
              This directory refers to the process accessing the /proc file
              system, and is identical to the /proc directory named by the
              process ID of the same process.

       /proc/slabinfo
              Information about kernel caches.  Since Linux 2.6.16 this file
              is present only if the CONFIG_SLAB kernel configuration option
              is enabled.  The columns in /proc/slabinfo are:

                  cache-name
                  num-active-objs
                  total-objs
                  object-size
                  num-active-slabs
                  total-slabs
                  num-pages-per-slab

              See slabinfo(5) for details.

       /proc/stat
              kernel/system statistics.  Varies with architecture.  Common
              entries include:

              cpu  3357 0 4313 1362393
                     The amount of time, measured in units of USER_HZ
                     (1/100ths of a second on most architectures, use
                     sysconf(_SC_CLK_TCK) to obtain the right value), that the
                     system spent in various states:

                     user   (1) Time spent in user mode.

                     nice   (2) Time spent in user mode with low priority
                            (nice).

                     system (3) Time spent in system mode.

                     idle   (4) Time spent in the idle task.  This value
                            should be USER_HZ times the second entry in the
                            /proc/uptime pseudo-file.

                     iowait (since Linux 2.5.41)
                            (5) Time waiting for I/O to complete.

                     irq (since Linux 2.6.0-test4)
                            (6) Time servicing interrupts.

                     softirq (since Linux 2.6.0-test4)
                            (7) Time servicing softirqs.

                     steal (since Linux 2.6.11)
                            (8) Stolen time, which is the time spent in other
                            operating systems when running in a virtualized
                            environment

                     guest (since Linux 2.6.24)
                            (9) Time spent running a virtual CPU for guest
                            operating systems under the control of the Linux
                            kernel.

                     guest_nice (since Linux 2.6.33)
                            (10) Time spent running a niced guest (virtual CPU
                            for guest operating systems under the control of
                            the Linux kernel).

              page 5741 1808
                     The number of pages the system paged in and the number
                     that were paged out (from disk).

              swap 1 0
                     The number of swap pages that have been brought in and
                     out.

              intr 1462898
                     This line shows counts of interrupts serviced since boot
                     time, for each of the possible system interrupts.  The
                     first column is the total of all interrupts serviced;
                     each subsequent column is the total for a particular
                     interrupt.

              disk_io: (2,0):(31,30,5764,1,2) (3,0):...
                     (major,disk_idx):(noinfo, read_io_ops, blks_read,
                     write_io_ops, blks_written)
                     (Linux 2.4 only)

              ctxt 115315
                     The number of context switches that the system underwent.

              btime 769041601
                     boot time, in seconds since the Epoch, 1970-01-01
                     00:00:00 +0000 (UTC).

              processes 86031
                     Number of forks since boot.

              procs_running 6
                     Number of processes in runnable state.  (Linux 2.5.45
                     onward.)

              procs_blocked 2
                     Number of processes blocked waiting for I/O to complete.
                     (Linux 2.5.45 onward.)

       /proc/swaps
              Swap areas in use.  See also swapon(8).

       /proc/sys
              This directory (present since 1.3.57) contains a number of files
              and subdirectories corresponding to kernel variables.  These
              variables can be read and sometimes modified using the /proc
              file system, and the (deprecated) sysctl(2) system call.

       /proc/sys/abi (since Linux 2.4.10)
              This directory may contain files with application binary
              information.  See the Linux kernel source file
              Documentation/sysctl/abi.txt for more information.

       /proc/sys/debug
              This directory may be empty.

       /proc/sys/dev
              This directory contains device-specific information (e.g.,
              dev/cdrom/info).  On some systems, it may be empty.

       /proc/sys/fs
              This directory contains the files and subdirectories for kernel
              variables related to file systems.

       /proc/sys/fs/binfmt_misc
              Documentation for files in this directory can be found in the
              Linux kernel sources in Documentation/binfmt_misc.txt.

       /proc/sys/fs/dentry-state (since Linux 2.2)
              This file contains information about the status of the directory
              cache (dcache).  The file contains six numbers, nr_dentry,
              nr_unused, age_limit (age in seconds), want_pages (pages
              requested by system) and two dummy values.

              * nr_dentry is the number of allocated dentries (dcache
                entries).  This field is unused in Linux 2.2.

              * nr_unused is the number of unused dentries.

              * age_limit is the age in seconds after which dcache entries can
                be reclaimed when memory is short.

              * want_pages is nonzero when the kernel has called
                shrink_dcache_pages() and the dcache isn't pruned yet.

       /proc/sys/fs/dir-notify-enable
              This file can be used to disable or enable the dnotify interface
              described in fcntl(2) on a system-wide basis.  A value of 0 in
              this file disables the interface, and a value of 1 enables it.

       /proc/sys/fs/dquot-max
              This file shows the maximum number of cached disk quota entries.
              On some (2.4) systems, it is not present.  If the number of free
              cached disk quota entries is very low and you have some awesome
              number of simultaneous system users, you might want to raise the
              limit.

       /proc/sys/fs/dquot-nr
              This file shows the number of allocated disk quota entries and
              the number of free disk quota entries.

       /proc/sys/fs/epoll (since Linux 2.6.28)
              This directory contains the file max_user_watches, which can be
              used to limit the amount of kernel memory consumed by the epoll
              interface.  For further details, see epoll(7).

       /proc/sys/fs/file-max
              This file defines a system-wide limit on the number of open
              files for all processes.  (See also setrlimit(2), which can be
              used by a process to set the per-process limit, RLIMIT_NOFILE,
              on the number of files it may open.)  If you get lots of error
              messages in the kernel log about running out of file handles
              (look for "VFS: file-max limit <number> reached"), try
              increasing this value:

                  echo 100000 > /proc/sys/fs/file-max

              The kernel constant NR_OPEN imposes an upper limit on the value
              that may be placed in file-max.

              If you increase /proc/sys/fs/file-max, be sure to increase
              /proc/sys/fs/inode-max to 3-4 times the new value of
              /proc/sys/fs/file-max, or you will run out of inodes.

              Privileged processes (CAP_SYS_ADMIN) can override the file-max
              limit.

       /proc/sys/fs/file-nr
              This (read-only) file contains three numbers: the number of
              allocated file handles (i.e., the number of files presently
              opened); the number of free file handles; and the maximum number
              of file handles (i.e., the same value as /proc/sys/fs/file-max).
              If the number of allocated file handles is close to the maximum,
              you should consider increasing the maximum.  Before Linux 2.6,
              the kernel allocated file handles dynamically, but it didn't
              free them again.  Instead the free file handles were kept in a
              list for reallocation; the "free file handles" value indicates
              the size of that list.  A large number of free file handles
              indicates that there was a past peak in the usage of open file
              handles.  Since Linux 2.6, the kernel does deallocate freed file
              handles, and the "free file handles" value is always zero.

       /proc/sys/fs/inode-max
              This file contains the maximum number of in-memory inodes.  On
              some (2.4) systems, it may not be present.  This value should be
              3-4 times larger than the value in file-max, since stdin, stdout
              and network sockets also need an inode to handle them.  When you
              regularly run out of inodes, you need to increase this value.

       /proc/sys/fs/inode-nr
              This file contains the first two values from inode-state.

       /proc/sys/fs/inode-state
              This file contains seven numbers: nr_inodes, nr_free_inodes,
              preshrink, and four dummy values.  nr_inodes is the number of
              inodes the system has allocated.  This can be slightly more than
              inode-max because Linux allocates them one page full at a time.
              nr_free_inodes represents the number of free inodes.  preshrink
              is nonzero when the nr_inodes > inode-max and the system needs
              to prune the inode list instead of allocating more.

       /proc/sys/fs/inotify (since Linux 2.6.13)
              This directory contains files max_queued_events,
              max_user_instances, and max_user_watches, that can be used to
              limit the amount of kernel memory consumed by the inotify
              interface.  For further details, see inotify(7).

       /proc/sys/fs/lease-break-time
              This file specifies the grace period that the kernel grants to a
              process holding a file lease (fcntl(2)) after it has sent a
              signal to that process notifying it that another process is
              waiting to open the file.  If the lease holder does not remove
              or downgrade the lease within this grace period, the kernel
              forcibly breaks the lease.

       /proc/sys/fs/leases-enable
              This file can be used to enable or disable file leases
              (fcntl(2)) on a system-wide basis.  If this file contains the
              value 0, leases are disabled.  A nonzero value enables leases.

       /proc/sys/fs/mqueue (since Linux 2.6.6)
              This directory contains files msg_max, msgsize_max, and
              queues_max, controlling the resources used by POSIX message
              queues.  See mq_overview(7) for details.

       /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
              These files allow you to change the value of the fixed UID and
              GID.  The default is 65534.  Some file systems support only
              16-bit UIDs and GIDs, although in Linux UIDs and GIDs are 32
              bits.  When one of these file systems is mounted with writes
              enabled, any UID or GID that would exceed 65535 is translated to
              the overflow value before being written to disk.

       /proc/sys/fs/pipe-max-size (since Linux 2.6.35)
              The value in this file defines an upper limit for raising the
              capacity of a pipe using the fcntl(2) F_SETPIPE_SZ operation.
              This limit applies only to unprivileged processes.  The default
              value for this file is 1,048,576.  The value assigned to this
              file may be rounded upward, to reflect the value actually
              employed for a convenient implementation.  To determine the
              rounded-up value, display the contents of this file after
              assigning a value to it.  The minimum value that can be assigned
              to this file is the system page size.

       /proc/sys/fs/protected_hardlinks (since Linux 3.6)
              When the value in this file is 0, no restrictions are placed on
              the creation of hard links (i.e., this is the historical
              behaviour before Linux 3.6).  When the value in this file is 1,
              a hard link can be created to a target file only if one of the
              following conditions is true:

              *  The caller has the CAP_FOWNER capability.

              *  The file system UID of the process creating the link matches
                 the owner (UID) of the target file (as described in
                 credentials(7), a process's file system UID is normally the
                 same as its effective UID).

              *  All of the following conditions are true:

                  ·  the target is a regular file;

                  ·  the target file does not have its set-user-ID permission
                     bit enabled;

                  ·  the target file does not have both its set-group-ID and
                     group-executable permission bits enabled; and

                  ·  the caller has permission to read and write the target
                     file (either via the file's permissions mask or because
                     it has suitable capabilities).

              The default value in this file is 0.  Setting the value to 1
              prevents a longstanding class of security issues caused by hard-
              link-based time-of-check, time-of-use races, most commonly seen
              in world-writable directories such as /tmp.  The common method
              of exploiting this flaw is to cross privilege boundaries when
              following a given hard link (i.e., a root process follows a hard
              link created by another user).  Additionally, on systems without
              separated partitions, this stops unauthorized users from
              "pinning" vulnerable set-user-ID and set-group-ID files against
              being upgraded by the administrator, or linking to special
              files.

       /proc/sys/fs/protected_symlinks (since Linux 3.6)
              When the value in this file is 0, no restrictions are placed on
              following symbolic links (i.e., this is the historical behaviour
              before Linux 3.6).  When the value in this file is 1, symbolic
              links are followed only in the following circumstances:

              *  the file system UID of the process following the link matches
                 the owner (UID) of the symbolic link (as described in
                 credentials(7), a process's file system UID is normally the
                 same as its effective UID);

              *  the link is not in a sticky world-writable directory; or

              *  the symbolic link and and its parent directory have the same
                 owner (UID)

              A system call that fails to follow a symbolic link because of
              the above restrictions returns the error EACCES in errno.

              The default value in this file is 0.  Setting the value to 1
              avoids a longstanding class of security issues based on time-of-
              check, time-of-use races when accessing symbolic links.

       /proc/sys/fs/suid_dumpable (since Linux 2.6.13)
              The value in this file determines whether core dump files are
              produced for set-user-ID or otherwise protected/tainted
              binaries.  Three different integer values can be specified:

              0 (default)
                     This provides the traditional (pre-Linux 2.6.13)
                     behavior.  A core dump will not be produced for a process
                     which has changed credentials (by calling seteuid(2),
                     setgid(2), or similar, or by executing a set-user-ID or
                     set-group-ID program) or whose binary does not have read
                     permission enabled.

              1 ("debug")
                     All processes dump core when possible.  The core dump is
                     owned by the file system user ID of the dumping process
                     and no security is applied.  This is intended for system
                     debugging situations only.  Ptrace is unchecked.

              2 ("suidsafe")
                     Any binary which normally would not be dumped (see "0"
                     above) is dumped readable by root only.  This allows the
                     user to remove the core dump file but not to read it.
                     For security reasons core dumps in this mode will not
                     overwrite one another or other files.  This mode is
                     appropriate when administrators are attempting to debug
                     problems in a normal environment.

                     Additionally, since Linux 3.6,
                     /proc/sys/kernel/core_pattern must either be an absolute
                     pathname or a pipe command, as detailed in core(5).
                     Warnings will be written to the kernel log if
                     core_pattern does not follow these rules, and no core
                     dump will be produced.

       /proc/sys/fs/super-max
              This file controls the maximum number of superblocks, and thus
              the maximum number of mounted file systems the kernel can have.
              You need increase only super-max if you need to mount more file
              systems than the current value in super-max allows you to.

       /proc/sys/fs/super-nr
              This file contains the number of file systems currently mounted.

       /proc/sys/kernel
              This directory contains files controlling a range of kernel
              parameters, as described below.

       /proc/sys/kernel/acct
              This file contains three numbers: highwater, lowwater, and
              frequency.  If BSD-style process accounting is enabled these
              values control its behavior.  If free space on file system where
              the log lives goes below lowwater percent accounting suspends.
              If free space gets above highwater percent accounting resumes.
              frequency determines how often the kernel checks the amount of
              free space (value is in seconds).  Default values are 4, 2 and
              30.  That is, suspend accounting if 2% or less space is free;
              resume it if 4% or more space is free; consider information
              about amount of free space valid for 30 seconds.

       /proc/sys/kernel/cap_last_cap (since Linux 3.2)
              See capabilities(7).

       /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
              This file holds the value of the kernel capability bounding set
              (expressed as a signed decimal number).  This set is ANDed
              against the capabilities permitted to a process during
              execve(2).  Starting with Linux 2.6.25, the system-wide
              capability bounding set disappeared, and was replaced by a per-
              thread bounding set; see capabilities(7).

       /proc/sys/kernel/core_pattern
              See core(5).

       /proc/sys/kernel/core_uses_pid
              See core(5).

       /proc/sys/kernel/ctrl-alt-del
              This file controls the handling of Ctrl-Alt-Del from the
              keyboard.  When the value in this file is 0, Ctrl-Alt-Del is
              trapped and sent to the init(8) program to handle a graceful
              restart.  When the value is greater than zero, Linux's reaction
              to a Vulcan Nerve Pinch (tm) will be an immediate reboot,
              without even syncing its dirty buffers.  Note: when a program
              (like dosemu) has the keyboard in "raw" mode, the ctrl-alt-del
              is intercepted by the program before it ever reaches the kernel
              tty layer, and it's up to the program to decide what to do with
              it.

       /proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)
              The value in this file determines who can see kernel syslog
              contents.  A value of 0 in this file imposes no restrictions.
              If the value is 1, only privileged users can read the kernel
              syslog.  (See syslog(2) for more details.)  Since Linux 3.4,
              only users with the CAP_SYS_ADMIN capability may change the
              value in this file.

       /proc/sys/kernel/domainname and /proc/sys/kernel/hostname
              can be used to set the NIS/YP domainname and the hostname of
              your box in exactly the same way as the commands domainname(1)
              and hostname(1), that is:

                  # echo 'darkstar' > /proc/sys/kernel/hostname
                  # echo 'mydomain' > /proc/sys/kernel/domainname

              has the same effect as

                  # hostname 'darkstar'
                  # domainname 'mydomain'

              Note, however, that the classic darkstar.frop.org has the
              hostname "darkstar" and DNS (Internet Domain Name Server)
              domainname "frop.org", not to be confused with the NIS (Network
              Information Service) or YP (Yellow Pages) domainname.  These two
              domain names are in general different.  For a detailed
              discussion see the hostname(1) man page.

       /proc/sys/kernel/hotplug
              This file contains the path for the hotplug policy agent.  The
              default value in this file is /sbin/hotplug.

       /proc/sys/kernel/htab-reclaim
              (PowerPC only) If this file is set to a nonzero value, the
              PowerPC htab (see kernel file
              Documentation/powerpc/ppc_htab.txt) is pruned each time the
              system hits the idle loop.

       /proc/sys/kernel/kptr_restrict (since Linux 2.6.38)
              The value in this file determines whether kernel addresses are
              exposed via /proc files and other interfaces.  A value of 0 in
              this file imposes no restrictions.  If the value is 1, kernel
              pointers printed using the %pK format specifier will be replaced
              with zeros unless the user has the CAP_SYSLOG capability.  If
              the value is 2, kernel pointers printed using the %pK format
              specifier will be replaced with zeros regardless of the user's
              capabilities.  The initial default value for this file was 1,
              but the default was changed to 0 in Linux 2.6.39.  Since Linux
              3.4, only users with the CAP_SYS_ADMIN capability can change the
              value in this file.

       /proc/sys/kernel/l2cr
              (PowerPC only) This file contains a flag that controls the L2
              cache of G3 processor boards.  If 0, the cache is disabled.
              Enabled if nonzero.

       /proc/sys/kernel/modprobe
              This file contains the path for the kernel module loader.  The
              default value is /sbin/modprobe.  The file is present only if
              the kernel is built with the CONFIG_MODULES (CONFIG_KMOD in
              Linux 2.6.26 and earlier) option enabled.  It is described by
              the Linux kernel source file Documentation/kmod.txt (present
              only in kernel 2.4 and earlier).

       /proc/sys/kernel/modules_disabled (since Linux 2.6.31)
              A toggle value indicating if modules are allowed to be loaded in
              an otherwise modular kernel.  This toggle defaults to off (0),
              but can be set true (1).  Once true, modules can be neither
              loaded nor unloaded, and the toggle cannot be set back to false.
              The file is present only if the kernel is built with the
              CONFIG_MODULES option enabled.

       /proc/sys/kernel/msgmax
              This file defines a system-wide limit specifying the maximum
              number of bytes in a single message written on a System V
              message queue.

       /proc/sys/kernel/msgmni (since Linux 2.4)
              This file defines the system-wide limit on the number of message
              queue identifiers.

       /proc/sys/kernel/msgmnb
              This file defines a system-wide parameter used to initialize the
              msg_qbytes setting for subsequently created message queues.  The
              msg_qbytes setting specifies the maximum number of bytes that
              may be written to the message queue.

       /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
              These files give substrings of /proc/version.

       /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
              These files duplicate the files /proc/sys/fs/overflowgid and
              /proc/sys/fs/overflowuid.

       /proc/sys/kernel/panic
              This file gives read/write access to the kernel variable
              panic_timeout.  If this is zero, the kernel will loop on a
              panic; if nonzero it indicates that the kernel should autoreboot
              after this number of seconds.  When you use the software
              watchdog device driver, the recommended setting is 60.

       /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
              This file controls the kernel's behavior when an oops or BUG is
              encountered.  If this file contains 0, then the system tries to
              continue operation.  If it contains 1, then the system delays a
              few seconds (to give klogd time to record the oops output) and
              then panics.  If the /proc/sys/kernel/panic file is also nonzero
              then the machine will be rebooted.

       /proc/sys/kernel/pid_max (since Linux 2.5.34)
              This file specifies the value at which PIDs wrap around (i.e.,
              the value in this file is one greater than the maximum PID).
              The default value for this file, 32768, results in the same
              range of PIDs as on earlier kernels.  On 32-bit platforms, 32768
              is the maximum value for pid_max.  On 64-bit systems, pid_max
              can be set to any value up to 2^22 (PID_MAX_LIMIT, approximately
              4 million).

       /proc/sys/kernel/powersave-nap (PowerPC only)
              This file contains a flag.  If set, Linux-PPC will use the "nap"
              mode of powersaving, otherwise the "doze" mode will be used.

       /proc/sys/kernel/printk
              The four values in this file are console_loglevel,
              default_message_loglevel, minimum_console_level, and
              default_console_loglevel.  These values influence printk()
              behavior when printing or logging error messages.  See syslog(2)
              for more info on the different loglevels.  Messages with a
              higher priority than console_loglevel will be printed to the
              console.  Messages without an explicit priority will be printed
              with priority default_message_level.  minimum_console_loglevel
              is the minimum (highest) value to which console_loglevel can be
              set.  default_console_loglevel is the default value for
              console_loglevel.

       /proc/sys/kernel/pty (since Linux 2.6.4)
              This directory contains two files relating to the number of UNIX
              98 pseudoterminals (see pts(4)) on the system.

       /proc/sys/kernel/pty/max
              This file defines the maximum number of pseudoterminals.

       /proc/sys/kernel/pty/nr
              This read-only file indicates how many pseudoterminals are
              currently in use.

       /proc/sys/kernel/random
              This directory contains various parameters controlling the
              operation of the file /dev/random.  See random(4) for further
              information.

       /proc/sys/kernel/real-root-dev
              This file is documented in the Linux kernel source file
              Documentation/initrd.txt.

       /proc/sys/kernel/reboot-cmd (Sparc only)
              This file seems to be a way to give an argument to the SPARC
              ROM/Flash boot loader.  Maybe to tell it what to do after
              rebooting?

       /proc/sys/kernel/rtsig-max
              (Only in kernels up to and including 2.6.7; see setrlimit(2))
              This file can be used to tune the maximum number of POSIX real-
              time (queued) signals that can be outstanding in the system.

       /proc/sys/kernel/rtsig-nr
              (Only in kernels up to and including 2.6.7.)  This file shows
              the number POSIX real-time signals currently queued.

       /proc/sys/kernel/sched_rr_timeslice_ms (since Linux 3.9)
              See sched_rr_get_interval(2).

       /proc/sys/kernel/sem (since Linux 2.4)
              This file contains 4 numbers defining limits for System V IPC
              semaphores.  These fields are, in order:

              SEMMSL  The maximum semaphores per semaphore set.

              SEMMNS  A system-wide limit on the number of semaphores in all
                      semaphore sets.

              SEMOPM  The maximum number of operations that may be specified
                      in a semop(2) call.

              SEMMNI  A system-wide limit on the maximum number of semaphore
                      identifiers.

       /proc/sys/kernel/sg-big-buff
              This file shows the size of the generic SCSI device (sg) buffer.
              You can't tune it just yet, but you could change it at compile
              time by editing include/scsi/sg.h and changing the value of
              SG_BIG_BUFF.  However, there shouldn't be any reason to change
              this value.

       /proc/sys/kernel/shm_rmid_forced (since Linux 3.1)
              If this file is set to 1, all System V shared memory segments
              will be marked for destruction as soon as the number of attached
              processes falls to zero; in other words, it is no longer
              possible to create shared memory segments that exist
              independently of any attached process.

              The effect is as though a shmctl(2) IPC_RMID is performed on all
              existing  segments as well as all segments created in the future
              (until this file is reset to 0).  Note that existing segments
              that are attached to no process will be immediately destroyed
              when this file is set to 1.  Setting this option will also
              destroy segments that were created, but never attached, upon
              termination of the process that created the segment with
              shmget(2).

              Setting this file to 1 provides a way of ensuring that all
              System V shared memory segments are counted against the resource
              usage and resource limits (see the description of RLIMIT_AS in
              getrlimit(2)) of at least one process.

              Because setting this file to 1 produces behavior that is
              nonstandard and could also break existing applications, the
              default value in this file is 0.  Only set this file to 1 if you
              have a good understanding of the semantics of the applications
              using System V shared memory on your system.

       /proc/sys/kernel/shmall
              This file contains the system-wide limit on the total number of
              pages of System V shared memory.

       /proc/sys/kernel/shmmax
              This file can be used to query and set the run-time limit on the
              maximum (System V IPC) shared memory segment size that can be
              created.  Shared memory segments up to 1GB are now supported in
              the kernel.  This value defaults to SHMMAX.

       /proc/sys/kernel/shmmni (since Linux 2.4)
              This file specifies the system-wide maximum number of System V
              shared memory segments that can be created.

       /proc/sys/kernel/sysrq
              This file controls the functions allowed to be invoked by the
              SysRq key.  By default, the file contains 1 meaning that every
              possible SysRq request is allowed (in older kernel versions,
              SysRq was disabled by default, and you were required to
              specifically enable it at run-time, but this is not the case any
              more).  Possible values in this file are:

                 0 - disable sysrq completely
                 1 - enable all functions of sysrq
                >1 - bit mask of allowed sysrq functions, as follows:
                        2 - enable control of console logging level
                        4 - enable control of keyboard (SAK, unraw)
                        8 - enable debugging dumps of processes etc.
                       16 - enable sync command
                       32 - enable remount read-only
                       64 - enable signalling of processes (term, kill, oom-
              kill)
                      128 - allow reboot/poweroff
                      256 - allow nicing of all real-time tasks

              This file is present only if the CONFIG_MAGIC_SYSRQ kernel
              configuration option is enabled.  For further details see the
              Linux kernel source file Documentation/sysrq.txt.

       /proc/sys/kernel/version
              This file contains a string like:

                  #5 Wed Feb 25 21:49:24 MET 1998

              The "#5" means that this is the fifth kernel built from this
              source base and the date behind it indicates the time the kernel
              was built.

       /proc/sys/kernel/threads-max (since Linux 2.3.11)
              This file specifies the system-wide limit on the number of
              threads (tasks) that can be created on the system.

       /proc/sys/kernel/zero-paged (PowerPC only)
              This file contains a flag.  When enabled (nonzero), Linux-PPC
              will pre-zero pages in the idle loop, possibly speeding up
              get_free_pages.

       /proc/sys/net
              This directory contains networking stuff.  Explanations for some
              of the files under this directory can be found in tcp(7) and
              ip(7).

       /proc/sys/net/core/somaxconn
              This file defines a ceiling value for the backlog argument of
              listen(2); see the listen(2) manual page for details.

       /proc/sys/proc
              This directory may be empty.

       /proc/sys/sunrpc
              This directory supports Sun remote procedure call for network
              file system (NFS).  On some systems, it is not present.

       /proc/sys/vm
              This directory contains files for memory management tuning,
              buffer and cache management.

       /proc/sys/vm/drop_caches (since Linux 2.6.16)
              Writing to this file causes the kernel to drop clean caches,
              dentries and inodes from memory, causing that memory to become
              free.

              To free pagecache, use echo 1 > /proc/sys/vm/drop_caches; to
              free dentries and inodes, use echo 2 > /proc/sys/vm/drop_caches;
              to free pagecache, dentries and inodes, use echo 3 >
              /proc/sys/vm/drop_caches.

              Because this is a nondestructive operation and dirty objects are
              not freeable, the user should run sync(8) first.

       /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
              If nonzero, this disables the new 32-bit memory-mapping layout;
              the kernel will use the legacy (2.4) layout for all processes.

       /proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)
              Control how to kill processes when an uncorrected memory error
              (typically a 2-bit error in a memory module) that cannot be
              handled by the kernel is detected in the background by hardware.
              In some cases (like the page still having a valid copy on disk),
              the kernel will handle the failure transparently without
              affecting any applications.  But if there is no other up-to-date
              copy of the data, it will kill processes to prevent any data
              corruptions from propagating.

              The file has one of the following values:

              1:  Kill all processes that have the corrupted-and-not-
                  reloadable page mapped as soon as the corruption is
                  detected.  Note this is not supported for a few types of
                  pages, like kernel internally allocated data or the swap
                  cache, but works for the majority of user pages.

              0:  Only unmap the corrupted page from all processes and kill
                  only a process that tries to access it.

              The kill is performed using a SIGBUS signal with si_code set to
              BUS_MCEERR_AO.  Processes can handle this if they want to; see
              sigaction(2) for more details.

              This feature is active only on architectures/platforms with
              advanced machine check handling and depends on the hardware
              capabilities.

              Applications can override the memory_failure_early_kill setting
              individually with the prctl(2) PR_MCE_KILL operation.

              Only present if the kernel was configured with
              CONFIG_MEMORY_FAILURE.

       /proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)
              Enable memory failure recovery (when supported by the platform)

              1:  Attempt recovery.

              0:  Always panic on a memory failure.

              Only present if the kernel was configured with
              CONFIG_MEMORY_FAILURE.

       /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
              Enables a system-wide task dump (excluding kernel threads) to be
              produced when the kernel performs an OOM-killing.  The dump
              includes the following information for each task (thread,
              process): thread ID, real user ID, thread group ID (process ID),
              virtual memory size, resident set size, the CPU that the task is
              scheduled on, oom_adj score (see the description of
              /proc/[pid]/oom_adj), and command name.  This is helpful to
              determine why the OOM-killer was invoked and to identify the
              rogue task that caused it.

              If this contains the value zero, this information is suppressed.
              On very large systems with thousands of tasks, it may not be
              feasible to dump the memory state information for each one.
              Such systems should not be forced to incur a performance penalty
              in OOM situations when the information may not be desired.

              If this is set to nonzero, this information is shown whenever
              the OOM-killer actually kills a memory-hogging task.

              The default value is 0.

       /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
              This enables or disables killing the OOM-triggering task in out-
              of-memory situations.

              If this is set to zero, the OOM-killer will scan through the
              entire tasklist and select a task based on heuristics to kill.
              This normally selects a rogue memory-hogging task that frees up
              a large amount of memory when killed.

              If this is set to nonzero, the OOM-killer simply kills the task
              that triggered the out-of-memory condition.  This avoids a
              possibly expensive tasklist scan.

              If /proc/sys/vm/panic_on_oom is nonzero, it takes precedence
              over whatever value is used in
              /proc/sys/vm/oom_kill_allocating_task.

              The default value is 0.

       /proc/sys/vm/overcommit_memory
              This file contains the kernel virtual memory accounting mode.
              Values are:

                     0: heuristic overcommit (this is the default)
                     1: always overcommit, never check
                     2: always check, never overcommit

              In mode 0, calls of mmap(2) with MAP_NORESERVE are not checked,
              and the default check is very weak, leading to the risk of
              getting a process "OOM-killed".  Under Linux 2.4 any nonzero
              value implies mode 1.  In mode 2 (available since Linux 2.6),
              the total virtual address space on the system is limited to (SS
              + RAM*(r/100)), where SS is the size of the swap space, and RAM
              is the size of the physical memory, and r is the contents of the
              file /proc/sys/vm/overcommit_ratio.

       /proc/sys/vm/overcommit_ratio
              See the description of /proc/sys/vm/overcommit_memory.

       /proc/sys/vm/panic_on_oom (since Linux 2.6.18)
              This enables or disables a kernel panic in an out-of-memory
              situation.

              If this file is set to the value 0, the kernel's OOM-killer will
              kill some rogue process.  Usually, the OOM-killer is able to
              kill a rogue process and the system will survive.

              If this file is set to the value 1, then the kernel normally
              panics when out-of-memory happens.  However, if a process limits
              allocations to certain nodes using memory policies (mbind(2)
              MPOL_BIND) or cpusets (cpuset(7)) and those nodes reach memory
              exhaustion status, one process may be killed by the OOM-killer.
              No panic occurs in this case: because other nodes' memory may be
              free, this means the system as a whole may not have reached an
              out-of-memory situation yet.

              If this file is set to the value 2, the kernel always panics
              when an out-of-memory condition occurs.

              The default value is 0.  1 and 2 are for failover of clustering.
              Select either according to your policy of failover.

       /proc/sys/vm/swappiness
              The value in this file controls how aggressively the kernel will
              swap memory pages.  Higher values increase aggressiveness, lower
              values decrease aggressiveness.  The default value is 60.

       /proc/sysrq-trigger (since Linux 2.4.21)
              Writing a character to this file triggers the same SysRq
              function as typing ALT-SysRq-<character> (see the description of
              /proc/sys/kernel/sysrq).  This file is normally writable only by
              root.  For further details see the Linux kernel source file
              Documentation/sysrq.txt.

       /proc/sysvipc
              Subdirectory containing the pseudo-files msg, sem and shm.
              These files list the System V Interprocess Communication (IPC)
              objects (respectively: message queues, semaphores, and shared
              memory) that currently exist on the system, providing similar
              information to that available via ipcs(1).  These files have
              headers and are formatted (one IPC object per line) for easy
              understanding.  svipc(7) provides further background on the
              information shown by these files.

       /proc/tty
              Subdirectory containing the pseudo-files and subdirectories for
              tty drivers and line disciplines.

       /proc/uptime
              This file contains two numbers: the uptime of the system
              (seconds), and the amount of time spent in idle process
              (seconds).

       /proc/version
              This string identifies the kernel version that is currently
              running.  It includes the contents of /proc/sys/kernel/ostype,
              /proc/sys/kernel/osrelease and /proc/sys/kernel/version.  For
              example:
            Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994

       /proc/vmstat (since Linux 2.6)
              This file displays various virtual memory statistics.

       /proc/zoneinfo (since Linux 2.6.13)
              This file display information about memory zones.  This is
              useful for analyzing virtual memory behavior.

NOTES
       Many strings (i.e., the environment and command line) are in the
       internal format, with subfields terminated by null bytes ('\0'), so you
       may find that things are more readable if you use od -c or tr "\000"
       "\n" to read them.  Alternatively, echo `cat <file>` works well.

       This manual page is incomplete, possibly inaccurate, and is the kind of
       thing that needs to be updated very often.

SEE ALSO
       cat(1), dmesg(1), find(1), free(1), ps(1), tr(1), uptime(1), chroot(2),
       mmap(2), readlink(2), syslog(2), slabinfo(5), hier(7), time(7), arp(8),
       hdparm(8), ifconfig(8), init(8), lsmod(8), lspci(8), mount(8),
       netstat(8), procinfo(8), route(8), sysctl(8)

       The Linux kernel source files: Documentation/filesystems/proc.txt and
       Documentation/sysctl/vm.txt.

COLOPHON
       This page is part of release 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



Linux                             2013-08-01                           PROC(5)