5.3. Moving root File Systems from a Single Path Device to a Multipath Device
If you have installed your system on a single-path device and later add another path to the root file system, you will need to move your root file system to a multipathed device. This section documents the procedure for moving from a single-path to a multipathed device.
After ensuring that you have installed the
device-mapper-multipathpackage, perform the following procedure:
- Execute the following command to create the
/etc/multipath.confconfiguration file, load the multipath module, and set
mpathconf --enableFor further information on using the
mpathconfcommand to set up multipathing, see Section 3.1, “Setting Up DM Multipath”.
- If the
find_multipathsconfiguration parameter is not set to
yes, edit the
blacklist_exceptionssections of the
/etc/multipath.conffile, as described in Section 4.2, “Configuration File Blacklist”.
- In order for multipath to build a multipath device on top of the root device as soon as it is discovered, enter the following command. This command also ensures that
find_multipathswill allow the device, even if it only has one path.
multipath -a root_devnameFor example, if the root device is
/dev/sdb, enter the following command.
multipath -a /dev/sdbwwid '3600d02300069c9ce09d41c4ac9c53200' added
- To confirm that your configuration file is set up correctly, you can enter the
multipathcommand and search the output for a line of the following format. This indicates that the command failed to create the multipath device.
date wwid: ignoring mapFor example, if the WWID if the device is 3600d02300069c9ce09d41c4ac9c53200, you would see a line in the output such as the following:
multipathOct 21 09:37:19 | 3600d02300069c9ce09d41c4ac9c53200: ignoring map
- To rebuild the
initramfsfile system with
multipath, execute the
dracutcommand with the following options:
dracut --force -H --add multipath
- Shut the machine down.
- Configure the FC switch so that other paths are visible to the machine.
- Boot the machine.
- Check whether the root file system ('/') is on the multipathed device.