NFS resource fault monitoring is specific to each NFS resource. The fault monitor of each resource checks the status of each shared path to monitor the file systems that the resource exports.
Before starting the NFS resource fault monitor probes, all the shared paths are read from the dfstab file and stored in memory. In each probe cycle, the probe performs the following steps.
If dfstab has been changed since the last read, the probe refreshes the memory.
If an error occurs while reading the dfstab file, the resource status is set to FAULTED, and the monitor skips the remainder of the checks in the current probe cycle.
The fault monitor probes all the shared paths in each iteration by performing stat() on the path.
If any path is not functional, the resource status is set to FAULTED.
The probe checks for the presence of NFS daemons (nfsd, mountd, lockd, statd) and rpcbind.
If any of these daemons are down, the resource status is set to FAULTED.
If all shared paths are valid and NFS daemons are present, the resource status is reset to ONLINE.