create a new array
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
or…
mdadm -C /dev/md0 -l1 -n2 /dev/sd[ab]1
add array to the configuration file:
mdadm --detail --scan >> /etc/mdadm.conf
or on debian (sigh)…
mdadm --detail --scan >> /etc/mdadm/mdadm.conf
can only remove failed disks from an array, so fail a disk:
mdadm --fail /dev/md0 /dev/sda1
remove the failed disk from the array:
mdadm --remove /dev/md0 /dev/sda1
fail and remove in a single step:
mdadm /dev/md0 --fail /dev/sda1 --remove /dev/sda1
add a new disk to an existing array (or replace a failed disk):
mdadm --add /dev/md0 /dev/sda1
verify an array
mdadm --detail /dev/md0
or, for all arrays…
cat /proc/mdstat
- output should contain
Ufor each member of the array - a failed disk status code is
F - degraded arrays will be missing disks
remove an arry (first, must be stopped)
mdadm --stop /dev/md0 ; mdadm --remove /dev/md0
better: test for successful stop
mdadm --stop /dev/md0 && mdadm --remove /dev/md0
remove the superblock from the array members’ partitions
mdadm --zero-superblock /dev/sda
copy a partition table from one disk to another
sfdisk -d /dev/sda | sfdisk /dev/sdb
this is not strictly a raid command, but often handy since raid arrays are usually composed of multiple, identical disks.
