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.\" -*- nroff -*-
.\" This file may be copied under the terms of the GNU Public License.
.\"
.TH E2MMPSTATUS 8 "February 2023" "E2fsprogs version 1.47.0"
.SH NAME
e2mmpstatus \- Check MMP status of an ext4 file system
.SH SYNOPSIS
.BR e2mmpstatus " [" \-i ]
.RI < file system >
.SH OPTIONS
.TP
.B \-i
prints out the MMP information rather than check it.
.SH DESCRIPTION
.B e2mmpstatus
is used to check Multiple-Mount Protection (MMP) status of an ext4
file system with the
.B mmp
feature enabled. The specified
.I file system
can be a device name (e.g.
.IR /dev/hdc1 ", " /dev/sdb2 ),
or an ext4 file system label or UUID, for example
.B UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd
or
.BR LABEL=root .
By default, the
.B e2mmpstatus
program checks whether it is safe to mount the file system without taking
the risk of mounting it more than once.
.PP
MMP (multiple-mount protection) is a feature that adds protection against
the file system being modified simultaneously by more than one node.
It is NOT safe to mount a file system when one of the following conditions
is true:
.br
1. e2fsck is running on the file system.
.br
2. the file system is in use by another node.
.br
3. The MMP block is corrupted or cannot be read for some reason.
.br
The
.B e2mmpstatus
program might wait for some time to see whether the MMP block is being
updated by any node during this period. The time taken depends on how
frequently the MMP block is being written by the other node.
.SH EXIT CODE
The exit code returned by
.B e2mmpstatus
is 0 when it is safe to mount the file system, 1 when the MMP block shows
the file system is in use on another node and it is NOT safe to mount
the file system, and 2 if some other failure occurred that prevents the
check from properly detecting the current MMP status.
.SH SEE ALSO
.BR dumpe2fs (8),
.BR e2fsck (8),
.BR fstab (5),
.BR fsck (8),
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