[clug] Booting CentOS 7 - no MDs?

Paul Wayper paulway at mabula.net
Sun Mar 4 10:25:27 UTC 2018

Hi all,

I have a weird problem booting my home server.  It's running CentOS 7 with a
4.13 kernel because that has the patches for compatibility with the AMD Ryzen
1500 chip.  However, each time I boot it comes up with an emergency boot
prompt; neither of the MD RAID 1 devices exist, and as a consequence the LVM
on top of them doesn't have all its devices but the root and swap LVs are
active and are therefore presenting block errors.  In order to fix this I have to:

1) `mdadm --assemble` the two devices.
2) `lvm lvchange -a n` to deactivate the root and swap LVs.
3) `lvm vgchange -a y` to enable all the LVs on the volume group.
4) Exit the emergency console.

I can't send logs, because all this happens before the pivot to root so none
of the file systems for logging are active.

After the system comes up, I can see this:

$ cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdc[0] sde[2]
      3906887488 blocks super 1.2 [2/2] [UU]
      bitmap: 3/30 pages [12KB], 65536KB chunk

md0 : active raid1 sdf1[0] sda1[2]
      2930134016 blocks super 1.2 [2/2] [UU]
      bitmap: 0/22 pages [0KB], 65536KB chunk

unused devices: <none>
$ cat /etc/mdadm/mdadm.conf
ARRAY /dev/md/0  metadata=1.2 UUID=42cc34da:1a48e6ec:f8015328:5a31ceaf
ARRAY /dev/md/1  metadata=1.2 UUID=6803957e:63a30967:4671f639:e681403b

Any ideas on what might be going wrong, and/or how to fix it?

Thanks people,


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