mount.nilfs2

MOUNT.NILFS2(8)             System Manager's Manual            MOUNT.NILFS2(8)



NAME
       mount.nilfs2 - mount a NILFS2 file system

SYNOPSIS
       mount -t nilfs2 [-finrvw] [-o options [,...]] device dir
       mount -t nilfs2 [-finrvw] [-o options [,...]] device | dir

       mount.nilfs2 [-fnrvw] [-o options [,...]] device dir

       mount.nilfs2 [-V]

DESCRIPTION
       mount.nilfs2 serves to attach a NILFS2 file system on the specified
       directory dir. It is intended to be executed from mount(8), and will
       invoke the garbage collector nilfs_cleanerd(8) after an actual mount
       system call has succeeded.  Conversely, umount.nilfs2(8) will shutdown
       the garbage collector before detaching the file system.

       The standard command line interface is the first form:
              mount -t nilfs2 [options] device dir
       This tells the kernel to attach the NILFS2 file system on device at the
       directory dir.  With the second form, the mount program tries to find
       out a missing device or dir argument from the /etc/fstab table.

       The third form, which directly invokes mount.nilfs2, is also usable
       since mount.nilfs2 maintains by itself the system mount state such as
       the list of mounted file systems described in /etc/mtab. However, the
       first or the second form is usually recommended because some expansive
       options are not supported by the third form.

OPTIONS
       The full set of options used by an invocation of mount(8) is determined
       by extracting the options from the fstab table, then applying any
       options specified by the -o argument, and finally applying a -r or -w
       option, when present.

       See mount(8) for the full set of options.  Commonly used options are as
       follows:

       -V     Output version.

       -f     Fakes mounting the file system, meaning that the actual system
              call will be skipped.  This option is used to add entries for
              devices that were mounted earlier with the -n option. It can
              also be used for invoking nilfs_cleanerd(8) skipped previously.

       -i     Don't call mount.nilfs2.  This disables garbage collection and
              handling of pseudo mount options.

       -n     Mount without writing in /etc/mtab.  This is necessary for
              example when /etc is on a read-only file system.

       -r     Mount the file system read-only.  A synonym is "-o ro".

       -v     Verbose mode.

       -w     Mount the file system read/write. This is the default. A synonym
              is "-o rw".

       -o     Options are specified with a -o flag followed by a comma
              separated string of options.  Some of these options are only
              useful when they appear in the /etc/fstab file.  For standard
              filesystem options, see mount(8).

NILFS2 SPECIFIC MOUNT OPTIONS
       The following options apply only to the NILFS2 filesystem.  They all
       follow the -o flag.

       barrier / nobarrier
              These options enable/disable (default is enabled) barrier writes
              for the block I/O to a lower device.  The barrier write serves
              an important role to ensure consistency of filesystems after a
              system crash or power failure.  NILFS2 uses this feature by
              default to assure the reliability.  For devices not supporting
              the barrier write, it will be disabled automatically and a
              warning will be logged.

       cp=checkpoint-number
              Specify the checkpoint-number of the snapshot to be mounted.
              Checkpoints and snapshots are listed by lscp(1).  Only the
              checkpoints marked as snapshot are mountable with this option.
              Note that the read-only mount option must be specified together.

       errors=continue / errors=remount-ro / errors=panic
              Define the behaviour when an error is encountered.  (Either
              ignore errors and just mark the file system erroneous and
              continue, or remount the file system read-only, or panic and
              halt the system.)  The default is remount-ro.  In earlier
              kernels than Linux 2.6.35, continue was the default.

       pp=protection-period
              Specify the protection-period for the cleaner daemon (in
              seconds). nilfs_cleanerd never deletes recent checkpoints whose
              elapsed time from its creation is smaller than protection-
              period.

       nogc   Disable garbage collection. The cleaner daemon will not be
              started.  It can be be started manually, but in that case it
              must also be stopped manually before unmounting.

       order=relaxed / order=strict
              Specify order semantics for file data.  Metadata is always
              written to follow the POSIX semantics about the order of
              filesystem operations.

              relaxed
                     Apply relaxed order semantics that allows modified data
                     blocks to be written to disk without making a checkpoint
                     if no metadata update is going.  This mode is equivalent
                     to the ordered data mode of the ext3 filesystem except
                     for the updates on data blocks still conserve atomicity.
                     This will improve synchronous write performance for
                     overwriting.  This is the default mode.

              strict Apply strict in-order semantics that preserves sequence
                     of all file operations including overwriting of data
                     blocks.  That means, it is guaranteed that no overtaking
                     of events occurs in the recovered file system after a
                     crash.  Unlike journaling filesystems, NILFS2 does not
                     write a same block twice to disk.  So there is no
                     significant performance degradation in comparison with
                     the relaxed mode except for file overwriting.

       norecovery
              Disable recovery of the filesystem on mount.  This disables
              every write access on the device for read-only mounts or
              snapshots.  This option will fail for r/w mounts on an unclean
              volume.

       discard / nodiscard
              These options enable/disable (default is disabled) the use of
              discard/TRIM commands.  The discard/TRIM commands are sent to
              the underlying block device when blocks are freed.  This is
              useful for SSD devices and sparse/thinly-provisioned LUNs.
              (since 2.6.34).

RETURN CODES
       The return codes of mount.nilfs2 conform to those of mount(8); the
       following codes could be returned (the bits can be ORed):

       0      success

       1      incorrect invocation or permissions

       2      system error (out of memory, cannot fork, no more loop devices)

       4      internal bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

AUTHOR
       mount.nilfs2 is written by Ryusuke Konishi
       <konishi.ryusuke@lab.ntt.co.jp> for NILFS2, based on the mount program
       included in the util-linux package.

AVAILABILITY
       mount.nilfs2 is part of the nilfs-utils package and is available from
       http://nilfs.sourceforge.net.

SEE ALSO
       nilfs(8), mount(8), umount.nilfs2(8), nilfs_cleanerd(8), lscp(1).



nilfs-utils version 2.2            Apr 2014                    MOUNT.NILFS2(8)