1NILFS(8)                    System Manager's Manual                   NILFS(8)
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NAME

6       NILFS - the new implementation of a log-structured file system
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SYNOPSIS

9       Overview of the NILFS file system and the related tools.
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DESCRIPTION

12       NILFS  is a log-structured file system developed for Linux.  NILFS pro‐
13       vides versioning capability of an entire  file  system  and  continuous
14       snapshotting  that allows users to restore files mistakenly overwritten
15       or destroyed a while ago.
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17       The current major version of NILFS is version 2, which is  referred  to
18       as  NILFS2.   NILFS2 is equipped with an online garbage collector (also
19       called cleaner) that reclaims disk space in the background with keeping
20       multiple snapshots.
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22       When  data is written or any change is made to a NILFS2 file system, it
23       automatically creates a checkpoint.  A checkpoint represents a  consis‐
24       tent  state of the NILFS2 file system of a certain instant.  It becomes
25       mountable after being changed into  a  snapshot.   A  snapshot  is  the
26       checkpoint  marked  not to be deleted by the cleaner.  NILFS2 creates a
27       number of checkpoints at regular intervals (unless there is no  change)
28       or  with synchronous writings.  There is no practical limit on the num‐
29       ber of checkpoints and snapshots.
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31       The following tools are available to  manage  the  checkpoint  and  the
32       snapshot:
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34       lscp        lists checkpoints or snapshots
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36       mkcp        makes a checkpoint or a snapshot
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38       chcp        changes an existing checkpoint to a snapshot or vice versa
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40       rmcp        invalidates specified checkpoint(s)
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42       These tools give the versioning capability to NILFS2; a user can select
43       significant versions among continuously  created  checkpoints  and  can
44       change them to snapshots to be preserved for long periods.
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46       Every  checkpoint  except for the snapshot will become unprotected from
47       the cleaner after a given period of time.  This period is controlled by
48       the   protection_period  parameter  defined  in  the  /etc/nilfs_clean‐
49       erd.conf(5) file.
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MOUNT OPTIONS

52       Refer to the mount.nilfs2(8).
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EXAMPLES

55       mkfs -t nilfs2 /dev/sdb1
56              creates a NILFS2 file system on a block device `/dev/sdb1'.
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58       mount -t nilfs2 /dev/sdb1 /nilfs
59              mounts the NILFS2 file system on a mount point `/nilfs' like  an
60              ordinary  POSIX file system.  This will invoke a cleaner process
61              nilfs_cleanerd(8)  through  an  external  mount  program   (i.e.
62              mount.nilfs2(8)).
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64       lscp   lists checkpoints created in the file system as follows:
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66               CNO        DATE     TIME  MODE  FLG      BLKCNT       ICNT
67                 1  2014-01-18 20:49:54   cp    -            4          2
68                 2  2014-01-18 20:51:45   cp    -         3990         11
69                 3  2014-01-18 20:51:45   cp    -         6058          3
70                 4  2014-01-18 20:51:49   cp    -         4807          6
71                 5  2014-01-18 20:51:49   cp    -          262          3
72               ...
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74       chcp ss 2
75              changes the checkpoint whose checkpoint-number is two to a snap‐
76              shot.  Then the checkpoint list will become as follows:
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78               CNO        DATE     TIME  MODE  FLG      BLKCNT       ICNT
79                 1  2014-01-18 20:49:54   cp    -            4          2
80                 2  2014-01-18 20:51:45   ss    -         3990         11
81                 3  2014-01-18 20:51:45   cp    -         6058          3
82                 4  2014-01-18 20:51:49   cp    -         4807          6
83                 5  2014-01-18 20:51:49   cp    -          262          3
84               ...
85
86       mount -t nilfs2 -r -o cp=2 /dev/sdb1 /snapshot
87              mounts the snapshot on another directory `/snapshot' as a  read-
88              only file system.  Here the snapshot mount requires at least two
89              options, a read-only option (-r or -o ro) and the cp option  (-o
90              cp=checkpoint-number).   Note that a read/write mount and one or
91              more snapshots are mountable independently, so the online backup
92              is possible through the snapshot mounts.
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94               # mount -t nilfs2
95               /dev/sdb1 on /nilfs type nilfs2 (rw,gcpid=13296)
96               /dev/sdb1 on /snapshot type nilfs2 (ro,cp=2)
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98       umount /nilfs
99              unmounts  the  NILFS2  file  system mounted on `/nilfs' and will
100              shutdown the nilfs_cleanerd(8) through an external  umount  pro‐
101              gram (umount.nilfs2(8)) for the read/write mount.
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AUTHORS

104       NILFS2 was developed by NILFS development team.
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SEE ALSO

107       mkfs.nilfs2(8),  mount.nilfs2(8),  umount.nilfs2(8), nilfs_cleanerd(8),
108       nilfs_cleanerd.conf(5), nilfs-tune(8), nilfs-clean(8), nilfs-resize(8),
109       lscp(1), mkcp(8), chcp(8), rmcp(8), lssu(1), dumpseg(8)
110
111       https://nilfs.sourceforge.io/
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115nilfs-utils version 2.2            Apr 2014                           NILFS(8)
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