sys-utils/fsfreeze.8

   1 .TH FSFREEZE 8 "July 2014" "util-linux" "System Administration"
   2 .SH NAME
   3 fsfreeze \- suspend access to a filesystem (Ext3/4, ReiserFS, JFS, XFS)
   4 .SH SYNOPSIS
   5 .B fsfreeze
   6 .BR \--freeze | \--unfreeze
   7 .I mountpoint
   8
   9 .SH DESCRIPTION
  10 .B fsfreeze
  11 suspends or resumes access to a filesystem.
  12 .PP
  13 .B fsfreeze
  14 halts any new access to the filesystem and creates a stable image on disk.
  15 .B fsfreeze
  16 is intended to be used with hardware RAID devices that support the creation
  17 of snapshots.
  18 .PP
  19 .B fsfreeze
  20 is unnecessary for
  21 .B device-mapper
  22 devices.  The device-mapper (and LVM) automatically freezes a filesystem
  23 on the device when a snapshot creation is requested.
  24 For more details see the
  25 .BR dmsetup (8)
  26 man page.
  27 .PP
  28 The
  29 .I mountpoint
  30 argument is the pathname of the directory where the filesystem
  31 is mounted.
  32 The filesystem must be mounted to be frozen (see
  33 .BR mount (8)).
  34 .PP
  35 Note that access-time updates are also suspended if the filesystem is mounted with
  36 the traditional atime behavior (mount option \fBstrictatime\fR, for more details see
  37 .BR mount (8)).
  38
  39 .SH OPTIONS
  40 .TP
  41 .BR \-f , " \-\-freeze"
  42 This option requests the specified a filesystem to be frozen from new
  43 modifications.  When this is selected, all ongoing transactions in the
  44 filesystem are allowed to complete, new write system calls are halted, other
  45 calls which modify the filesystem are halted, and all dirty data, metadata, and
  46 log information are written to disk.  Any process attempting to write to the
  47 frozen filesystem will block waiting for the filesystem to be unfrozen.
  48 .sp
  49 Note that even after freezing, the on-disk filesystem can contain
  50 information on files that are still in the process of unlinking.
  51 These files will not be unlinked until the filesystem is unfrozen
  52 or a clean mount of the snapshot is complete.
  53 .TP
  54 .BR \-u , " \-\-unfreeze"
  55 This option is used to un-freeze the filesystem and allow operations to
  56 continue.  Any filesystem modifications that were blocked by the freeze are
  57 unblocked and allowed to complete.
  58 .TP
  59 .BR \-V , " \-\-version"
  60 Display version information and exit.
  61 .TP
  62 .BR \-h , " \-\-help"
  63 Display help text and exit.
  64 .SH FILESYSTEM SUPPORT
  65 This command will work only if filesystem supports has support for freezing.
  66 List of these filesystems include (2016-12-18)
  67 .BR btrfs ,
  68 .BR ext2/3/4 ,
  69 .BR f2fs ,
  70 .BR jfs ,
  71 .BR nilfs2 ,
  72 .BR reiserfs ,
  73 and
  74 .BR xfs .
  75 Previous list may be incomplete, as more filesystems get support.  If in
  76 doubt easiest way to know if a filesystem has support is create a small
  77 loopback mount and test freezing it.
  78 .SH AUTHOR
  79 .PP
  80 Written by Hajime Taira.
  81 .SH NOTES
  82 .PP
  83 This man page is based on
  84 .BR xfs_freeze (8).
  85 .SH SEE ALSO
  86 .BR mount (8)
  87 .SH AVAILABILITY
  88 The fsfreeze command is part of the util-linux package and is available from
  89 https://www.kernel.org/pub/linux/utils/util-linux/.