| .\" -*- nroff -*- |
| .\" This file may be copied under the terms of the GNU Public License. |
| .\" |
| .TH E2MMPSTATUS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@" |
| .SH NAME |
| e2mmpstatus \- Check MMP status of an ext4 filesystem |
| .SH SYNOPSIS |
| .BR e2mmpstatus " [" \-i ] |
| .RI < filesystem > |
| .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 |
| filesystem with the |
| .B mmp |
| feature enabled. The specified |
| .I filesystem |
| can be a device name (e.g. |
| .IR /dev/hdc1 ", " /dev/sdb2 ), |
| or an ext4 filesystem 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 filesystem without taking |
| the risk of mounting it more than once. |
| .PP |
| 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: |
| .br |
| \ 1. e2fsck is running on the filesystem. |
| .br |
| \ 2. the filesystem 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 filesystem, 1 when the MMP block shows |
| the filesystem is in use on another 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. |
| .SH SEE ALSO |
| .BR dumpe2fs (8), |
| .BR e2fsck (8), |
| .BR fstab (5), |
| .BR fsck (8), |
