I am running Ubuntu Server 12.04. I did apt-get upgrade and received a warning from mdadm.

update-initramfs: Generating /boot/initrd.img-3.11.0-24-generic
W: mdadm: the array /dev/md3 with UUID e3d153f0:6edf1702:1f51fb89:78ee93fe
W: mdadm: is currently active, but it is not listed in mdadm.conf. if
W: mdadm: it is needed for boot, then YOUR SYSTEM IS NOW UNBOOTABLE!
W: mdadm: please inspect the output of /usr/share/mdadm/mkconf, compare
W: mdadm: it to /etc/mdadm/mdadm.conf, and make the necessary changes.
W: mdadm: the array /dev/md1 with UUID 76492e25:648c4dcd:1f51fb89:78ee93fe
W: mdadm: is currently active, but it is not listed in mdadm.conf. if
W: mdadm: it is needed for boot, then YOUR SYSTEM IS NOW UNBOOTABLE!
W: mdadm: please inspect the output of /usr/share/mdadm/mkconf, compare
W: mdadm: it to /etc/mdadm/mdadm.conf, and make the necessary changes.

My current mdadm.conf is:

# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default, scan all partitions (/proc/partitions) for MD superblocks.
# alternatively, specify devices to scan, using wildcards if desired.
DEVICE partitions

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# instruct the monitoring daemon where to send mail alerts
MAILADDR root

# definitions of existing MD arrays

# This file was auto-generated on Tue, 11 May 2010 20:53:30 +0200
# by mkconf $Id$

ARRAY /dev/md1 level=raid1 num-devices=2 devices=/dev/sda1,/dev/sdb1
ARRAY /dev/md3 level=raid1 num-devices=2 devices=/dev/sda3,/dev/sdb3

The config generated by /usr/share/mdadm/mkconf is:

# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default (built-in), scan all partitions (/proc/partitions) and all
# containers for MD superblocks. alternatively, specify devices to scan, using
# wildcards if desired.
#DEVICE partitions

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# instruct the monitoring daemon where to send mail alerts
MAILADDR root

# definitions of existing MD arrays
ARRAY /dev/md1 UUID=76492e25:648c4dcd:1f51fb89:78ee93fe
ARRAY /dev/md3 UUID=e3d153f0:6edf1702:1f51fb89:78ee93fe

The warning says that /dev/md1 and /dev/md3 are not listed even though they are in the config. Is it okay change the config to the second one or will this cause problems?

up vote 1 down vote accepted

The only difference I see is this line:

#DEVICE partitions

This is commented out in the generated config file but not yours. I'd just uncomment that and commit the changes. Warnings like that tend to be a "head's up" thing rather than an actual problem if the configurations line up.

  • Is there no difference between ARRAY /dev/md1 level=raid1 num-devices=2 devices=/dev/sda1,/dev/sdb1 and ARRAY /dev/md1 UUID=76492e25:648c4dcd:1f51fb89:78ee93fe ? – Ripster Jul 7 '14 at 14:56
  • Well okay, they're different, but mdadm can identify the arrays in more than one way. As long as the UUID is right, the array will work since it matches. That's why your line works (since /dev/md1 is indeed made from your listed devices). – Nathan C Jul 7 '14 at 14:59

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