Where Does mdadm Store RAID Config?
mdadm assembles arrays from superblocks with persistent details in /etc/mdadm/mdadm.conf.
Last updated
mdadm finds arrays through metadata on the disks themselves. Superblocks on each member name the array and its members, so assembly works even without config. The mdadm.conf file in /etc/mdadm records those details for reliable boot assembly.
Generate the file by scanning existing arrays rather than hand writing UUIDs. Initramfs must include the file to assemble root arrays early. Monitor health through mdstat and smart data together.
Where mdadm stores this, by platform
/etc/mdadm/mdadm.conf
Array definitions by UUID for boot assembly live here. Disk superblocks hold the same truth. Update initramfs after edits.
Frequently asked questions
How do I generate mdadm.conf?
Scan with mdadm detail scan and append the output to the file. Verify UUIDs match mdstat before rebooting. Update initramfs so early boot sees it.
Why did my array not assemble on boot?
The config or initramfs predates the array change. Regenerate both after adding members. Check dmesg for superblock mismatches.
Notice an outdated path? Let us know.