After issuing `umount -a` the GFS2 fs hangs when mounting it

Solution Verified - Updated

Environment

  • Red Hat Enterprise Linux Server 5 (with the High Availability and Resilient Storage Add Ons)
  • Red Hat Enterprise Linux Server 6 (with the High Availability and Resilient Storage Add Ons)

Issue

  • After issuing umount -a the GFS2 fs hangs when mounting it

Resolution

Do not use the command umount -a on a Red Hat Enterprise Linux Server 5/6 (with the High Availability and Resilient Storage Add Ons) cluster.

Root Cause

The GFS and GFS2 filesystems require that the /sys/kernel/config of type configfs be mounted. That mount point is where the DLM information is located and DLM is used by GFS and GFS2. Unmounting the /sys/kernel/config mount point will cause your cluster to become unstable, because DLM is used for more than just GFS and GFS2.

The filesystem /sys/kernel/config of type configfs is mounted when cman is started and is unmounted when cman is stopped.

Diagnostic Steps

  • Is the service cman started?
  • Is the configfs filesystem mounted to the directory /sys/kernel/config? If the filesystem is mounted correctly, then it should look something like this below:
$ mount | grep "/sys/kernel/config" 
none on /sys/kernel/config type configfs (rw)

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