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I am using Arch Linux. I have three functioning RAID arrays via MDADM:

~ cat /etc/mdadm.conf ARRAY /dev/md0 metadata=1.2 name=beast:0 UUID=564fbbac:07f9bbeb:07ef9229:1d8fd77e ARRAY /dev/md1 metadata=1.2 name=beast:1 UUID=7559b085:3b4715cc:59205fdd:12c0db08 ARRAY /dev/md2 metadata=1.2 name=beast:2 UUID=2dddbf33:26249617:ef8f8b65:c9670bdb

I have three directories in /run/media that I try to automount these mdadm arrays via fstab:

#THE FOLLOWING SHOULD WORK BUT AUTOMOUNT FAILS!!!!! #UUID=564fbbac:07f9bbeb:07ef9229:1d8fd77e /run/media/tcarpent/MDADM_SYSRAID ntfs-3g auto,user,rw,exec,nofail 0 0 /dev/md0 /run/media/tcarpent/MDADM_SYSRAID ntfs-3g auto,user,rw,exec,nofail 0 0 #THE FOLLOWING SHOULD WORK BUT AUTOMOUNT FAILS!!!!! #UUID=7559b085:3b4715cc:59205fdd:12c0db08 /run/media/tcarpent/MDADM_MISCRAID ext4 auto,user,rw,exec,nofail 0 0 /dev/md1 /run/media/tcarpent/MDADM_MISCRAID ext4 auto,user,rw,exec,nofail 0 0 #THE FOLLOWING SHOULD WORK BUT AUTOMOUNT FAILS!!!!! #UUID=2dddbf33:26249617:ef8f8b65:c9670bdb /run/media/tcarpent/MDADM_MEDIARAID ext4 auto,user,rw,exec,nofail 0 0 /dev/md2 /run/media/tcarpent/MDADM_MEDIARAID ext4 auto,user,rw,exec,nofail 0 0

Using the commented out UUID lines, automount does not work. I see the drive as 'active but not mounted' in webmin, but am required to mount it, and enter my password, then the drive mounts. However, with the /dev/,,, lines, automount works, no password required.

What gives? I've been told to ALWAYS fstab with UUIDs and never device names so I want to fix this.

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The UUID seen in mdadm.conf are related to the MD drivers.

The UUID used in fstab are related to filesytems.

What you need are the filesystem UUID numbers. You can get them with a command line

sudo dumpe2fs /dev/md0 | grep UUID

So in my case:

$ grep md/0 /etc/mdadm/mdadm.conf ARRAY /dev/md/0 metadata=1.2 UUID=d634adc8:69deedd8:d491a79e:69aeff78 $ sudo dumpe2fs /dev/md0 | grep UUID dumpe2fs 1.42.12 (29-Aug-2014) Filesystem UUID: 195237da-8825-45fb-abf7-a62895bd0967 $ grep boot /etc/fstab UUID=195237da-8825-45fb-abf7-a62895bd0967 /boot ext4 defaults 0 2

So we can see the UUID used is the filesystem UUID and not the MD UUID.

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  • So this command works for md1 and md2, but gives tjhe followinfg for md0: 'sudo dumpe2fs /dev/md0 | grep UUID 28.6s  Sun 14 Aug 2016 08:10:57 AM EDT dumpe2fs 1.43.1 (08-Jun-2016) dumpe2fs: Bad magic number in super-block while trying to open /dev/md0' Commented Aug 14, 2016 at 12:19
  • /dev/md0 is an ntfs-3g partition, whereas md1 and md2 are not, does that have to do with it? Commented Aug 14, 2016 at 12:22
  • Yes, I don't know if ntfs-3g had a UUID you can use this way. If there is a UUID then you'll need to find another way of finding it; dumpe2fs only works with ext2/3/4 filesystems. Commented Aug 14, 2016 at 12:40
  • 2
    The blkid command will also give you all UUIDs regardless of filesystem, and faster than waiting for dump to finish Commented Sep 28, 2019 at 0:10

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