nilfs

NILFS(8)                    System Manager's Manual                   NILFS(8)



NAME
       NILFS - the new implementation of a log-structured file system

SYNOPSIS
       Overview of the NILFS file system and the related tools.

DESCRIPTION
       NILFS is a log-structured file system developed for Linux.  NILFS
       provides versioning capability of an entire file system and continuous
       snapshotting that allows users to restore files mistakenly overwritten
       or destroyed a while ago.

       The current major version of NILFS is version 2, which is referred to
       as NILFS2.  NILFS2 is equipped with an online garbage collector (also
       called cleaner) that reclaims disk space in the background with keeping
       multiple snapshots.

       When data is written or any change is made to a NILFS2 file system, it
       automatically creates a checkpoint.  A checkpoint represents a
       consistent state of the NILFS2 file system of a certain instant.  It
       becomes mountable after being changed into a snapshot.  A snapshot is
       the checkpoint marked not to be deleted by the cleaner.  NILFS2 creates
       a number of checkpoints at regular intervals (unless there is no
       change) or with synchronous writings.  There is no practical limit on
       the number of checkpoints and snapshots.

       The following tools are available to manage the checkpoint and the
       snapshot:

       lscp        lists checkpoints or snapshots

       mkcp        makes a checkpoint or a snapshot

       chcp        changes an existing checkpoint to a snapshot or vice versa

       rmcp        invalidates specified checkpoint(s)

       These tools give the versioning capability to NILFS2; a user can select
       significant versions among continuously created checkpoints and can
       change them to snapshots to be preserved for long periods.

       Every checkpoint except for the snapshot will become unprotected from
       the cleaner after a given period of time.  This period is controlled by
       the protection_period parameter defined in the
       /etc/nilfs_cleanerd.conf(5) file.

MOUNT OPTIONS
       Refer to the mount.nilfs2(8).

EXAMPLES
       mkfs -t nilfs2 /dev/sdb1
              creates a NILFS2 file system on a block device `/dev/sdb1'.

       mount -t nilfs2 /dev/sdb1 /nilfs
              mounts the NILFS2 file system on a mount point `/nilfs' like an
              ordinary POSIX file system.  This will invoke a cleaner process
              nilfs_cleanerd(8) through an external mount program (i.e.
              mount.nilfs2(8)).

       lscp   lists checkpoints created in the file system as follows:

               CNO        DATE     TIME  MODE  FLG      BLKCNT       ICNT
                 1  2014-01-18 20:49:54   cp    -            4          2
                 2  2014-01-18 20:51:45   cp    -         3990         11
                 3  2014-01-18 20:51:45   cp    -         6058          3
                 4  2014-01-18 20:51:49   cp    -         4807          6
                 5  2014-01-18 20:51:49   cp    -          262          3
               ...

       chcp ss 2
              changes the checkpoint whose checkpoint-number is two to a
              snapshot.  Then the checkpoint list will become as follows:

               CNO        DATE     TIME  MODE  FLG      BLKCNT       ICNT
                 1  2014-01-18 20:49:54   cp    -            4          2
                 2  2014-01-18 20:51:45   ss    -         3990         11
                 3  2014-01-18 20:51:45   cp    -         6058          3
                 4  2014-01-18 20:51:49   cp    -         4807          6
                 5  2014-01-18 20:51:49   cp    -          262          3
               ...

       mount -t nilfs2 -r -o cp=2 /dev/sdb1 /snapshot
              mounts the snapshot on another directory `/snapshot' as a read-
              only file system.  Here the snapshot mount requires at least two
              options, a read-only option (-r or -o ro) and the cp option (-o
              cp=checkpoint-number).  Note that a read/write mount and one or
              more snapshots are mountable independently, so the online backup
              is possible through the snapshot mounts.

               # mount -t nilfs2
               /dev/sdb1 on /nilfs type nilfs2 (rw,gcpid=13296)
               /dev/sdb1 on /snapshot type nilfs2 (ro,cp=2)

       umount /nilfs
              unmounts the NILFS2 file system mounted on `/nilfs' and will
              shutdown the nilfs_cleanerd(8) through an external umount
              program (umount.nilfs2(8)) for the read/write mount.

AUTHORS
       NILFS2 was developed by NILFS development team.

SEE ALSO
       mkfs.nilfs2(8), mount.nilfs2(8), umount.nilfs2(8), nilfs_cleanerd(8),
       nilfs_cleanerd.conf(5), nilfs-tune(8), nilfs-clean(8), nilfs-resize(8),
       lscp(1), mkcp(8), chcp(8), rmcp(8), lssu(1), dumpseg(8)

       http://nilfs.sourceforge.net/



nilfs-utils version 2.2            Apr 2014                           NILFS(8)