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MeSo2
Asked: 2020-03-23 10:40:36 +0800 CST

mdadm: error opening /dev/md0: No such file or directory

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in the title is what I get when running: sudo mdadm --run /dev/md0

I build and configured a RAID 1 on Ubuntu 19.10 using mdadm not too long ago. Now it stop working. What do I need to do to get it back?

sudo fdisk -l

...

Disk /dev/sda: 7.28 TiB, 8001563222016 bytes, 15628053168 sectors
Disk model: ST8000DM004-2CX1
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/sdc: 223.58 GiB, 240057409536 bytes, 468862128 sectors
Disk model: KINGSTON SH103S3
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 1E539CE0-BE56-4F34-B3D3-7BF02003458F

Device         Start       End   Sectors   Size Type
/dev/sdc1       2048    264191    262144   128M BIOS boot
/dev/sdc2     264192 452069375 451805184 215.4G EFI System
/dev/sdc3  452069376 468860927  16791552     8G Linux swap

Disk /dev/sdb: 7.28 TiB, 8001563222016 bytes, 15628053168 sectors
Disk model: ST8000DM004-2CX1
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

...

sudo mdadm --detail --scan

(returned nothing)

sudo cat /proc/mdstat

Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
unused devices: <none>

sudo update-initramfs -u

update-initramfs: Generating /boot/initrd.img-5.3.0-42-generic
W: initramfs-tools configuration sets RESUME=UUID=cfd81e4d-9eb5-443a-b27a-ff669b8185dc
W: but no matching swap device is available.
I: The initramfs will attempt to resume from /dev/sdc3
I: (UUID=30bf601b-9470-4a3a-af7c-2aedce2cb0ca)
I: Set the RESUME variable to override this.
raid mdadm 19.10

1 Answers

  1. after doing some more digging I found this error (a triple-entry for md0) in mdadm.conf.

    # This configuration was auto-generated on Fri, 06 Mar 2020 22:24:51 -0800 by mkconf
ARRAY /dev/md0 metadata=1.2 name=nas:0 UUID=6e49ac17:91ff6793:a755436d:56c8a49c

ARRAY /dev/md0 level=raid1 num-devices=2 metadata=1.2 name=nas:0 UUID=6e49ac17:91ff6793:a755436d:56c8a49c
   devices=/dev/sda,/dev/sdb

ARRAY /dev/md0 level=raid1 num-devices=2 metadata=1.2 name=nas:0 UUID=6e49ac17:91ff6793:a755436d:56c8a49c
   devices=/dev/sda,/dev/sdb

    so I modified it to 

    # This configuration was auto-generated on Fri, 06 Mar 2020 22:24:51 -0800 by mkconf
ARRAY /dev/md0 level=raid1 num-devices=2 metadata=1.2 name=nas:0 UUID=6e49ac17:91ff6793:a755436d:56c8a49c
   devices=/dev/sda,/dev/sdb

    and ran sudo update-initramfs -u and sudo mdadm --assemble --scan which resulted in:

    mdadm: /dev/md0 has been started with 2 drives.

    and now I go my drive back

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