E2MMPSTATUS(8) System Manager's Manual E2MMPSTATUS(8)
NAME
e2mmpstatus - Check MMP status of an ext4 filesystem
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 filesystem with the mmp feature enabled. The specified
filesystem can be a device name (e.g. /dev/hdc1, /dev/sdb2), or an
ext4 filesystem 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 filesys-
tem without taking the risk of mounting it more than once.
MMP (multiple-mount protection) is a feature that adds protection
against the filesystem being modified simultaneously by more than one
node. It is NOT safe to mount a filesystem when one of the following
conditions is true:
1. e2fsck is running on the filesystem.
2. the filesystem 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
filesystem, 1 when the MMP block shows the filesystem is in use on an-
other node and it is NOT safe to mount the filesystem, 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 1.45.6 March 2020 E2MMPSTATUS(8)