Here is a quick recipe for how to troubleshooting with the multipathd

multipathd -k command is an interactive interface to the multipathd daemon. Entering this command brings up an interactive multipath console. After entering this command, you can enter help to get a list of available commands, you can enter a interactive command, or you can enter >CTRL-D to quit.

The multipathd interactive console can be used to troubleshoot problems you may be having with your system. For example, the following command sequence displays the multipath configuration, including the defaults, before exiting the console. See the IBM article "Tricks with Multipathd" for more examples.

 

Displya multipath configuration

# multipathd -k
  > > show config
  > > CTRL-D

Reload multipath.conf

The following command sequence ensures that multipath has picked up any changes to the multipath.conf,

# multipathd -k
> > reconfigure
> > CTRL-D

Check path

Use the following command sequence to ensure that the path checker is working properly.

# multipathd -k
> > show paths
> > CTRL-D

Display path status

# multipathd -k
> > show multipaths status
> > CTRL-D

Display topology

# multipathd -k
> > show topology
> > CTRL-D

Fail a path

# multipathd -k
> > fail path sdc
> > CTRL-D

Delete a path

# multipathd -k
> > del path sdc
> > CTRL-D

Suspend a path

# multipathd -k
> > suspend map mpath0
> > CTRL-D

Resume a path

# multipathd -k
> > resume map mpath0
> > CTRL-D

Show blacklist

# multipathd -k
> > show blacklist
> > CTRL-D

Error message

THE /var/log/messages FILE
Events creates using these methods will be logged into the messages file just as a failing event, however the will be tagged as "operator".

Dec 11 10:19:49 k2 multipathd: mpath0: fail path 8:32 (operator)
Dec 11 10:24:18 k2 multipathd: mpath0: suspend (operator)
Dec 11 10:30:26 k2 multipathd: mpath0: resume (operator)  

Note:

Commands can also be streamed into multipathd using stdin like so:

# echo 'show config' | multipathd -k