Here are some multipath command examples, before we get started, let's see how many options does multipath command has. We'll be just focusing on most useful options.

 

Useful multipath Command Options

Table Useful multipath Command Options describes some options of the multipath command that you might find useful.

Option Description
-l Display the current multipath configuration gathered from sysfs and the device mapper.
-ll Display the current multipath configuration gathered from sysfs, the device mapper, and all other available components on the system.
-f
Remove the named multipath device.
-F Remove all unused multipath devices.
-v lvl  Verbosity level
          . 0 no output
          . 1 print created devmap names only
          . 2 default verbosity
          . 3 print debug information
-d  Dry run, do not create or update devmaps
-r  Force devmap reload

Multipath Command Output

When you create, modify, or list a multipath device, you get a printout of the current device setup. The format is as follows. For each multipath device:

   action_if_any: alias (wwid_if_different_from_alias) dm_device_name_if_known vendor,product
   size=size features='features' hwhandler='hardware_handler' wp=write_permission_if_known

For each path group:

  -+- policy='scheduling_policy' prio=prio_if_known
  status=path_group_status_if_known

For each path:

   `- host:channel:id:lun devnode major:minor dm_status_if_known path_status
  online_status

For example, the output of a multipath command might appear as follows:

  3600d0230000000000e13955cc3757800 dm-1 WINSYS,SF2372
  size=269G features='0' hwhandler='0' wp=rw
  |-+- policy='round-robin 0' prio=1 status=active
  | `- 6:0:0:0 sdb 8:16  active ready  running
  `-+- policy='round-robin 0' prio=1 status=enabled
    `- 7:0:0:0 sdf 8:80  active ready  running

If the path is up and ready for I/O, the status of the path is ready or active. If the path is down, the status is faulty or failed. The path status is updated periodically by the multipathd daemon based on the polling interval defined in the /etc/multipath.conf file.

The dm status is similar to the path status, but from the kernel's point of view. The dm status has two states: failed, which is analogous to faulty, and active which covers all other path states. Occasionally, the path state and the dm state of a device will temporarily not agree.

The possible values for online_status are running and offline. A status of offline means that the SCSI device has been disabled.

When a multipath device is being created or modified , the path group status, the dm device name, the write permissions, and the dm status are not known. Also, the features are not always correct

 

Multipath Queries with multipath Command

You can use the -l and -ll options of the multipath command to display the current multipath configuration. The -l option displays multipath topology gathered from information in sysfs and the device mapper. The -ll option displays the information the -l displays in addition to all other available components of the system.

When displaying the multipath configuration, there are three verbosity levels you can specify with the -v option of the multipath command. Specifying -v0 yields no output. Specifying -v1 outputs the created or updated multipath names only, which you can then feed to other tools such as kpartx. Specifying -v2 prints all detected paths, multipaths, and device maps.

The default verbosity level of multipath is 2 and can be globally modified by defining the verbosity attribute in the defaults section of multipath.conf.

The following example shows the output of a multipath -l command.

# multipath -l
  3600d0230000000000e13955cc3757800 dm-1 WINSYS,SF2372
  size=269G features='0' hwhandler='0' wp=rw
  |-+- policy='round-robin 0' prio=1 status=active
  | `- 6:0:0:0 sdb 8:16  active ready  running
  `-+- policy='round-robin 0' prio=1 status=enabled
    `- 7:0:0:0 sdf 8:80  active ready  running

The following example shows the output of a multipath -ll command.

# multipath -ll
  3600d0230000000000e13955cc3757801 dm-10 WINSYS,SF2372
  size=269G features='0' hwhandler='0' wp=rw
  |-+- policy='round-robin 0' prio=1 status=enabled
  | `- 19:0:0:1 sdc 8:32  active ready  running
  `-+- policy='round-robin 0' prio=1 status=enabled
    `- 18:0:0:1 sdh 8:112 active ready  running
    3600d0230000000000e13955cc3757803 dm-2 WINSYS,SF2372
    size=125G features='0' hwhandler='0' wp=rw
    `-+- policy='round-robin 0' prio=1 status=active
      |- 19:0:0:3 sde 8:64  active ready  running
        `- 18:0:0:3 sdj 8:144 active ready  running

Remove multipath devices with multipath Command

 You can use the -f and -F options of the multipath command to remove multipath paths.

-f option is to remove one named multipath device

# multipath -f dm-10

-F option is to remove all unused devices

# multipath -F

Verbose output with multipath command

#multipath -v 2

Verbosity level
          . 0 no output
          . 1 print created devmap names only
          . 2 default verbosity
          . 3 print debug information

Force reload device map with multipath Command

#multipath -r

multipath Command dry run

# multipath -d -F