In linux operating system device mapping through multipath is widely used. Here, we can give you some example how we will use the multipath commands in Linux server
➤ Normally multipath device has a Word Wide Identifier (WWID), which is globally unique and unchanging.
➤ When new devices are brought under the control of DM-Multipath, the new devices may be seen in three different places under the /dev directory: /dev/mapper/mpathn, /dev/mpath/mpathn, and /dev/dm-n
➤ The devices in /dev/mapper are created early in the boot process. Use these devices to access the multipathed devices, for example when creating logical volumes.
The devices in /dev/mpath are provided as a convenience so that all multipathed devices can be seen in one directory. These devices are created by the udev device manager and may not be available on startup when the system needs to access them.
➤ Normally multipath device has a Word Wide Identifier (WWID), which is globally unique and unchanging.
➤ When new devices are brought under the control of DM-Multipath, the new devices may be seen in three different places under the /dev directory: /dev/mapper/mpathn, /dev/mpath/mpathn, and /dev/dm-n
➤ The devices in /dev/mapper are created early in the boot process. Use these devices to access the multipathed devices, for example when creating logical volumes.
The devices in /dev/mpath are provided as a convenience so that all multipathed devices can be seen in one directory. These devices are created by the udev device manager and may not be available on startup when the system needs to access them.
Note: Do not use these devices for creating logical volumes or filesystems
➤ Any devices of the form /dev/dm-n are for internal use only and should never be used.
Please find the multipath syntax which we used in the Linux operating system.
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 -> Verbosity level
. 0 no output
. 1 print created devmap names only
. 2 default verbosity
. 3 print debug information
. 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
⧪ How to display the current multipath configuration with all information.
[root@localhost~]# multipath -ll
Dec 21 11:27:17 | multipath.conf line 35, invalid keyword: selector
mpathf (3600c0ff00019e9e9dc94c25801000000) dm-6 HP,MSA 2040 SAN
size=466G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=70 status=active
|- 1:0:0:4 sdg 8:96 active ready running
|- 2:0:0:4 sdj 8:144 active ready running
|- 1:0:1:4 sdq 65:0 active ready running
`- 2:0:1:4 sdt 65:48 active ready running
⧪ How to remove multipath devices with multipath Command
[root@localhost~]# multipath -f mpathf
Note: if we use -F option then it is remove all unused devices.
⧪ How to Force reload device map with multipath Command
[root@localhost~]# multipath -r
⧪ How to display the current multipath configuration with all information.
[root@localhost~]# multipath -ll
Dec 21 11:27:17 | multipath.conf line 35, invalid keyword: selector
mpathf (3600c0ff00019e9e9dc94c25801000000) dm-6 HP,MSA 2040 SAN
size=466G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=70 status=active
|- 1:0:0:4 sdg 8:96 active ready running
|- 2:0:0:4 sdj 8:144 active ready running
|- 1:0:1:4 sdq 65:0 active ready running
`- 2:0:1:4 sdt 65:48 active ready running
⧪ How to remove multipath devices with multipath Command
[root@localhost~]# multipath -f mpathf
Note: if we use -F option then it is remove all unused devices.
⧪ How to Force reload device map with multipath Command
[root@localhost~]# multipath -r
