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.TH xfs_freeze 8
.SH NAME
xfs_freeze \- suspend access to an XFS filesystem
.SH SYNOPSIS
.B xfs_freeze
[
.B \-f
|
.B \-u
]
.I mount-point
.br
.B xfs_freeze \-V
.fi
.SH DESCRIPTION
.B xfs_freeze
suspends and resumes access to an XFS filesystem (see
.BR xfs (5)).
.PP
.B xfs_freeze
halts new access to the filesystem and creates a stable image on disk.
.B xfs_freeze
is intended to be used with volume managers and hardware RAID devices
that support the creation of snapshots.
.PP
The
.I mount-point
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
.PP
The
.B \-f
flag requests the specified XFS 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.
.PP
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.
.PP
The
.B \-u
flag 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.
.PP
The
.B \-V
flag prints the version number and exits.
.PP
Unless
.B \-V
is specified, one of
.B \-f
or
.B \-u
must be supplied to
.BR xfs_freeze .
.SH NOTES
A copy of a frozen XFS filesystem will usually have the same universally
unique identifier (UUID) as the original, and thus may be prevented from
being mounted.
The XFS
.B nouuid
mount option can be used to circumvent this issue.
.PP
In Linux kernel version 2.6.29, the interface which XFS uses to freeze
and unfreeze was elevated to the VFS, so that this tool can now be
used on many other Linux filesystems.
.SH SEE ALSO
.BR xfs (5),
.BR lvm (8),
.BR mount (8).
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