3.5.1 Matrix Server Command Reference

Chapter 1: Matrix Server Commands 29

Description

This command is provided with MxFS-Linux. NLM is the locking protocol

used by NFS. By default, it is disabled in MxFS-Linux. If necessary, NLM can

be enabled; however, you should be aware of the following caveat:

• File locks granted by the NFS server are cluster-coherent. When a failover

occurs, the locks are released by the original server and the client

automatically reclaims them on the new server (the backup node).

However, during the period after the lock is released, another client or

application may compete for and win the lock. Some NFS clients will

return an error to the client applications if the lock cannot be reclaimed.

Other clients (for example, the Linux 2.6 NFS client) will not return any

error. If no error is returned by the client, the application may proceed

under the false assumption that the lock has been granted. Data

corruption may be the result.

To prevent this situation, locking should be enabled only if your clients are

partitioned so that all clients needing a particular lock are using the same

Virtual NFS Service IP address. If a failover occurs, all of the clients will

lose their locks. They can then reclaim those same locks on the new node

without conflicts from outside clients.

The options are as follows:

-q

Show the current status of NLM locking in the cluster (either enabled or

disabled).

-e

Enable NLM locking in the cluster. No reboot is necessary; the change is

effective almost immediately and may affect clients.

-d

Disable NLM locking in the cluster. No reboot is necessary; the change is

effective almost immediately and may affect clients.

mxpasswd – add users or change passwords

Synopsis

/opt/polyserve/bin/mxpasswd