FSFREEZE(8)                  System Administration                 FSFREEZE(8)

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

       fsfreeze --freeze|--unfreeze mountpoint

       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
       devices 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

       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)).

       -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
              information  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
              unlinking.   These files will not be unlinked until the filesys-
              tem 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.

       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.

       Written by Hajime Taira.

       This man page is based on xfs_freeze(8).


       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)
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