fsfreeze

FSFREEZE(8)                  System Administration                 FSFREEZE(8)

NAME
       fsfreeze - suspend access to a filesystem (Ext3/4, ReiserFS, JFS, XFS)

SYNOPSIS
       fsfreeze --freeze|--unfreeze mountpoint

DESCRIPTION
       fsfreeze suspends or resumes access to a filesystem.

       fsfreeze  halts  any  new access to the filesystem and creates a stable
       image on disk.  fsfreeze is intended to be used with hardware RAID  de-
       vices that support the creation of snapshots.

       fsfreeze  is  unnecessary for device-mapper devices.  The device-mapper
       (and LVM) automatically freezes a filesystem on the device when a snap-
       shot  creation  is  requested.  For more details see the dmsetup(8) man
       page.

       The mountpoint argument is the pathname  of  the  directory  where  the
       filesystem  is  mounted.   The  filesystem must be mounted to be frozen
       (see mount(8)).

       Note that access-time updates are also suspended if the  filesystem  is
       mounted  with the traditional atime behavior (mount option strictatime,
       for more details see mount(8)).

OPTIONS
       -f, --freeze
              This option requests the specified a  filesystem  to  be  frozen
              from  new  modifications.   When  this  is selected, all ongoing
              transactions in the filesystem  are  allowed  to  complete,  new
              write  system  calls  are  halted,  other calls which modify the
              filesystem are halted, and all dirty data, metadata, and log in-
              formation  are written to disk.  Any process attempting to write
              to the frozen filesystem will block waiting for  the  filesystem
              to be unfrozen.

              Note  that  even after freezing, the on-disk filesystem can con-
              tain information on files that are still in the process  of  un-
              linking.   These files will not be unlinked until the filesystem
              is unfrozen or a clean mount of the snapshot is complete.

       -u, --unfreeze
              This option is used to un-freeze the filesystem and allow opera-
              tions  to  continue.   Any  filesystem  modifications  that were
              blocked by the freeze are unblocked and allowed to complete.

       -V, --version
              Display version information and exit.

       -h, --help
              Display help text and exit.

FILESYSTEM SUPPORT
       This command will work only if  filesystem  supports  has  support  for
       freezing.   List  of  these  filesystems  include  (2016-12-18)  btrfs,
       ext2/3/4, f2fs, jfs, nilfs2, reiserfs, and xfs.  Previous list  may  be
       incomplete,  as  more filesystems get support.  If in doubt easiest way
       to know if a filesystem has support is create a  small  loopback  mount
       and test freezing it.

AUTHOR
       Written by Hajime Taira.

NOTES
       This man page is based on xfs_freeze(8).

SEE ALSO
       mount(8)

AVAILABILITY
       The fsfreeze command is part of the util-linux package and is available
       from https://www.kernel.org/pub/linux/utils/util-linux/.

util-linux                         July 2014                       FSFREEZE(8)