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)