| .TH FSFREEZE 8 "July 2014" "util-linux" "System Administration" |
| .SH NAME |
| fsfreeze \- suspend access to a filesystem (Ext3/4, ReiserFS, JFS, XFS) |
| .SH SYNOPSIS |
| .B fsfreeze |
| .BR \--freeze | \--unfreeze |
| .I mountpoint |
| |
| .SH DESCRIPTION |
| .B fsfreeze |
| suspends or resumes access to a filesystem. |
| .PP |
| .B fsfreeze |
| halts any new access to the filesystem and creates a stable image on disk. |
| .B fsfreeze |
| is intended to be used with hardware RAID devices that support the creation |
| of snapshots. |
| .PP |
| .B fsfreeze |
| is unnecessary for |
| .B 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 |
| .BR dmsetup (8) |
| man page. |
| .PP |
| The |
| .I mountpoint |
| argument is the pathname of the directory where the filesystem |
| is mounted. |
| The filesystem must be mounted to be frozen (see |
| .BR mount (8)). |
| .PP |
| Note that access-time updates are also suspended if the filesystem is mounted with |
| the traditional atime behavior (mount option \fBstrictatime\fR, for more details see |
| .BR mount (8)). |
| |
| .SH OPTIONS |
| .TP |
| .BR \-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. |
| .sp |
| 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. |
| .TP |
| .BR \-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. |
| .TP |
| .BR \-V , " \-\-version" |
| Display version information and exit. |
| .TP |
| .BR \-h , " \-\-help" |
| Display help text and exit. |
| .SH FILESYSTEM SUPPORT |
| This command will work only if filesystem supports has support for freezing. |
| List of these filesystems include (2016-12-18) |
| .BR btrfs , |
| .BR ext2/3/4 , |
| .BR f2fs , |
| .BR jfs , |
| .BR nilfs2 , |
| .BR reiserfs , |
| and |
| .BR 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. |
| .SH AUTHOR |
| .PP |
| Written by Hajime Taira. |
| .SH NOTES |
| .PP |
| This man page is based on |
| .BR xfs_freeze (8). |
| .SH SEE ALSO |
| .BR mount (8) |
| .SH AVAILABILITY |
| The fsfreeze command is part of the util-linux package and is available from |
| https://www.kernel.org/pub/linux/utils/util-linux/. |