2 .\" This file may be copied under the terms of the GNU Public License.
4 .TH E2MMPSTATUS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
6 e2mmpstatus \- Check MMP status of an ext4 file system
8 .BR e2mmpstatus " [" \-i ]
13 prints out the MMP information rather than check it.
16 is used to check Multiple-Mount Protection (MMP) status of an ext4
19 feature enabled. The specified
21 can be a device name (e.g.
22 .IR /dev/hdc1 ", " /dev/sdb2 ),
23 or an ext4 file system label or UUID, for example
24 .B UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd
29 program checks whether it is safe to mount the file system without taking
30 the risk of mounting it more than once.
32 MMP (multiple-mount protection) is a feature that adds protection against
33 the file system being modified simultaneously by more than one node.
34 It is NOT safe to mount a file system when one of the following conditions
37 1. e2fsck is running on the file system.
39 2. the file system is in use by another node.
41 3. The MMP block is corrupted or cannot be read for some reason.
45 program might wait for some time to see whether the MMP block is being
46 updated by any node during this period. The time taken depends on how
47 frequently the MMP block is being written by the other node.
49 The exit code returned by
51 is 0 when it is safe to mount the file system, 1 when the MMP block shows
52 the file system is in use on another node and it is NOT safe to mount
53 the file system, and 2 if some other failure occurred that prevents the
54 check from properly detecting the current MMP status.