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 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 snapshot  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 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  contain  information  on
              files that are still in the process of unlinking.  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 operations  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/.