Mount Failing Silently – Troubleshooting Ext4 Filesystems

ext4filesystemsmount

I'm trying to mount a device but without success.
The strange thing is that the mount command succeeds and return exit code 0, but the device is not mounted.
Any idea on why this happens or how to investigate it?
Please see the example below:

[root@mymachine ~]# blkid -o list
device         fs_type  label     mount point        UUID
-----------------------------------------------------------------------------------------
/dev/xvda1     xfs                /                  29342a0b-e20f-4676-9ecf-dfdf02ef6683
/dev/xvdy      ext4               /vols/data         72c23c30-2704-42ec-9518-533c182e2b22
/dev/xvdb      swap               <swap>             990ff722-158c-4ad5-963a-0bc9e1e2b17a
/dev/xvdx      ext4               (not mounted)      956b5553-d8b4-4ffe-830c-253e1cb10a2f
[root@mymachine ~]# grep /dev/xvdx /etc/fstab
/dev/xvdx /vols/data5 ext4 defaults 0 0
[root@mymachine ~]# mount -a; echo $?
0
[root@mymachine ~]# blkid -o list
device         fs_type  label     mount point        UUID
-----------------------------------------------------------------------------------------
/dev/xvda1     xfs                /                  29342a0b-e20f-4676-9ecf-dfdf02ef6683
/dev/xvdy      ext4               /vols/data         72c23c30-2704-42ec-9518-533c182e2b22
/dev/xvdb      swap               <swap>             990ff722-158c-4ad5-963a-0bc9e1e2b17a
/dev/xvdx      ext4               (not mounted)      956b5553-d8b4-4ffe-830c-253e1cb10a2f
[root@mymachine ~]# mount /dev/xvdx /vols/data5; echo $?
0
[root@mymachine ~]# blkid -o list
device         fs_type  label     mount point        UUID
-----------------------------------------------------------------------------------------
/dev/xvda1     xfs                /                  29342a0b-e20f-4676-9ecf-dfdf02ef6683
/dev/xvdy      ext4               /vols/data         72c23c30-2704-42ec-9518-533c182e2b22
/dev/xvdb      swap               <swap>             990ff722-158c-4ad5-963a-0bc9e1e2b17a
/dev/xvdx      ext4               (not mounted)      956b5553-d8b4-4ffe-830c-253e1cb10a2f
[root@mymachine ~]#

Full fstab:

[root@mymachine ~]# cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Mon May  1 18:59:01 2017
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=29342a0b-e20f-4676-9ecf-dfdf02ef6683 /                       xfs     defaults        0 0
/dev/xvdb swap swap defaults,nofail 0 0
/dev/xvdy /vols/data ext4 defaults 0 0
/dev/xvdx /vols/data5 ext4 defaults 0 0

Best Answer

Normally mount doesn't return 0 if there have been problems. When I had a similar problem, the reason was that systemd unmounted the filesystem immediately after the mount.

You can try strace mount /dev/xvdx /vols/data5 to see the result of the syscall. You can also try mount /dev/xvdx /vols/data5; ls -li /vols/data5 to see whether something is mounted immediately after the mount command.

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