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The multiple devices are variously called "underlying devices" and "RAID devices" in the documentation. On this WIKI page they are always "underlying devices".
md device file names: /dev/md<n> and /dev/md/<n>)
Originally md device files were /dev/md[[:digit:]]+. Now /dev/md/[[:digit:]]+ is preferred.
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If the md device provides the file system including /boot or is an LVM PV (physical volume) then /etc/mdadm/mdadm.conf must be re-populated as shown below and the initramfs re-generated by:
update-initramfs -u
Removal
For example:
mdadm --manage /dev/md2 --fail /dev/sd[ab]1 mdadm --manage /dev/md2 --remove /dev/sd[ab]1 mdadm --manage /dev/md2 --stop mdadm --zero-superblock /dev/sd[ab]1
Replacing an underlying device
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Mode | device before options | Options | Notes |
|---|---|---|---|
| --assemble | Y | bitmap, uuid, super-minor, name, config, scan, run, force, update, no-degraded | |
| --build | Y | ||
| --create | Y | ||
| --grow | N | ||
| --incremental | No options | ||
| --misc | N | ||
| --manage | Y | add, remove, fail, set-faulty, run, stop, readonly, readwrite | --manage may be omitted |
| --monitor | No device |
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Troubleshooting
initrd fails to assemble md devices
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