Problem booting from madam RAID1 array: Device or resource busy

[bobbus2]

Hi, I'm trying to boot from an mdadm RAID1 array on 14.04.

From the Grub2 console I can see and access the files on the raid Array


ls
> (hd1) (hd1,msdos1) (hd1,msdos2) (md/0) (md/1)

set ROOT=(md/1)
ls /
>initrd.img vmlinuz bin/ boot/ dev/ .... and all the expected folders



When I continue to boot from the array ...


linux /vmlinuz root=/dev/md1 nodmraid bootdegraded=true bootdelay=2000
initrd /initrd.img
boot


... it fails to mount md1 to the system root with the message:


mounting /dev/md1 on /root failed: Device or Resource busy


Additional information:
- md0 on sdb1 is SWAP & md1 on sdb2 is the system array
- using UUID to identify md1 makes no difference
- incrementing the delay to the max 10000 makes no difference
- sda has working installation on 14.04 and can mount md1 to /mnt with no problem
- the array is degraded, having only one disk, but assembles and mounts correctly other than boot.

One thought ... I had to include mdraid1x on the grub install just to be able to see the array ...


grub-install --modules=mdraid1x /dev/sdb

... are there any other modules I need to pre-load on install?


Any help appreciated.

[bobbus2]

Update:

I can access md1 immediately I get a prompt (initramfs or busy box). When checking the delay times it looks like bootdelay / rootdelay is simply being ignored and the kernel is trying to load the roots asap.

[bobbus2]

The answer is that initramfs was trying to mount the array to / (root) before the array had assembled. The rootdelay command on loading the kernel is ignored .... seems like a bug to me.

The solution was to add a delay script into the initramfs sequence to allow time for the array to assemble.




echo “sleep 60" > /etc/initramfs-tools/scripts/init-premount/delay_for_raid_array_to_build_before_mounting

update-initramfs -u


Lots of hours wasted because the documented 'root delay' kernel command doesn't work :(

[baldrick-free]

The script needs to be executable, so:

echo “sleep 60" > /etc/initramfs-tools/scripts/init-premount/delay_for_raid_array_to_build_before_mounting
chmod a+x /etc/initramfs-tools/scripts/init-premount/delay_for_raid_array_to_build_before_mounting
update-initramfs -u

[lopaka-z]

The answer is that initramfs was trying to mount the array to / (root) before the array had assembled. The rootdelay command on loading the kernel is ignored .... seems like a bug to me.

The solution was to add a delay script into the initramfs sequence to allow time for the array to assemble.




echo “sleep 60" > /etc/initramfs-tools/scripts/init-premount/delay_for_raid_array_to_build_before_mounting

update-initramfs -u


Lots of hours wasted because the documented 'root delay' kernel command doesn't work :(


Thanks so much for sharing this! Because of this, instead of spending 20hrs working on this same problem, I only had to waste 10hrs :) Thanks again!

[pmackinney]

Thanks here also. Same problem, solution worked perfectly. A bit more detail on how to fix:

After booting from Ubuntu Live CD:

$ sudo su -
# cat /proc/mdstat
Personalities : ...
md127 : active raid1 sda[1] sdj[0]
78150656 blocks [2/2] [UU] ...
# ls -l /dev/md127*
/dev/md127 /dev/md127p1 /dev/md127p2 /dev/md127p3
# blkid /dev/md127p2
/dev/md127p2: UUID="01234567-89ab-cdef-0123-0123456789ab" TYPE="ext4"
I know that md127p2 is the right partition, and the UUID was the same as grub's "root=UUID=..." argument, so let's try the fix!

# mount /dev/md127p2 /mnt
# for D in /dev /dev/pts /proc /sys; do mount -o bind $D /mnt$D; done
# chroot /mnt
# echo ... (see bobbus2's post)
# chmod ... (see baldrick-free's follow-up)
# udate-initramfs -u
# exit
# shutdown -r now
And it boots!