E2MMPSTATUS(8) System Manager's Manual E2MMPSTATUS(8)
NAME
e2mmpstatus - Check MMP status of an ext4 file system
SYNOPSIS
e2mmpstatus [-i] <filesystem>
OPTIONS
-i prints out the MMP information rather than check it.
DESCRIPTION
e2mmpstatus is used to check Multiple-Mount Protection (MMP) status of
an ext4 file system with the mmp feature enabled. The specified file
system can be a device name (e.g. /dev/hdc1, /dev/sdb2), or an ext4
file system label or UUID, for example
UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root. By default,
the e2mmpstatus program checks whether it is safe to mount the file
system without taking the risk of mounting it more than once.
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:
1. e2fsck is running on the file system.
2. the file system is in use by another node.
3. The MMP block is corrupted or cannot be read for some reason.
The 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.
EXIT CODE
The exit code returned by 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.
SEE ALSO
dumpe2fs(8), e2fsck(8), fstab(5), fsck(8),
E2fsprogs version 1.47.0 February 2023 E2MMPSTATUS(8)
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