What happens if two NFS shares are exported with the fsid=0 option?

Solution Unverified - Updated

Environment

  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux (RHEL) Server 7, 8 or 9 (with the High Availability and/or Resilient Storage Add Ons)
  • Pacemaker
  • NFS
  • Multiple entries in /etc/exports with fsid=0

Issue

  • Two shares are exported with fsid=0 option through NFS.
  • Which share will be considered as root share and will be mounted with the command:
mount nfsserver.example.com:/ /mount/point

Resolution

When the two shares are exported through NFS in RHEL cluster with the fsid=0 option, then the share that will appear first in the /etc/exports file will be mounted as root share.

Root Cause

fsid=0 - Export a directory over NFS v4. For example /sales. NFSv4 has a concept of a "root" of the overall exported filesystem.

The export point exported with fsid=0 will be used as this root. The /sales directory will be root for clients. For example, if the NFS server has /sales/data1 and /sales/data2 subdirectories, then clients would see them as /data1 and /data2 directory.

An NFS server may only export one directory with the fsid=0 option.

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