Step through mdadm commands to inspect, assemble and mount a manual RAID recovery. 12.01.2026 | reading time: 3 min A degraded RAID appeared after a disk failure; can you bring it back online without rebuilding from scratch He will inspect device metadata, assemble the array and mount it to recover data. Hands-on recovery example Follow this real command sequence to inspect devices, assemble a degraded array and mount it for recovery ```bash # examine the member device for a valid superblock mdadm --examine /dev/sdb1 # sample output # /dev/sdb1: # Magic : a92b4efc # Version : 1.2 # UUID : 12345678:9abcdef0:11223344:55667788 # Number : 0 # Events : 42 # assemble the array explicitly mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1 # if array refuses to start use --run to force starting a degraded array mdadm --assemble --run /dev/md0 /dev/sdb1 # verify kernel view cat /proc/mdstat # sample output # Personalities : [raid1] # md0 : active raid1 sdb1[0] sdc1[1] # 104320 blocks super 1.2 [2/1] [U_] # mount the filesystem and access files mount -t ext4 /dev/md0 /mnt/raid ``` Key parameters and precautions Always inspect with `mdadm --examine` before touching devices; the metadata UUID, role and events tell the story and avoid guesswork; use `--assemble --run` to start a degraded array but avoid `--force` unless you understand the risk; if a disk is marked failed remove it with `mdadm --manage --remove` and add a replacement with `mdadm --add`; remember to update `mdadm.conf` and your initramfs if you want automatic assembly at boot. Other helpers to know Use `lsblk` and `blkid` to confirm device names and filesystems, `parted` or `fdisk` to check partition layouts, `udevadm` to debug device naming, and `smartctl` to check for impending disk failure; combine these tools to script safe recovery steps or to automate monitoring. Ready for the next challenge Manual assembly teaches the mechanics of Linux software RAID and gives immediate control in emergencies; to deepen expertise pursue formal certification like CompTIA Linux+ or LPIC-1 and consider intensive exam preparation at bitsandbytes.academy to turn hands on skill into recognized credentials. Join Bits & Bytes Academy First class LINUX exam preparation. storage filesystem troubleshooting backup utilities
