Bug#791794: RAID device not active during boot
The problem might be related to
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=789152.
However, in my case everything seems to be fine as long as all harddisks
(within the RAID) are working.
The Problem appears only if during boot one (or more) disk(s) out of the
RAID device have a problem.
The problem might be related to the fact that jessie comes with a new
init system which has a stricter handling of failing "auto" mounts
during boot. If it fails to mount an "auto" mount, systemd will drop to
an emergency shell rather than continuing the boot - see release-notes
(section 5.6.1):
https://www.debian.org/releases/stable/amd64/release-notes/ch-information.en.html#systemd-upgrade-default-init-system
For example:
If you have installed your system to a RAID1 device and the system is
faced with a power failure which (might at the same time) causes a
damage to one of your harddisks (out of this RAID1 device) your system
will (during boot) drop to an emergency shell rather than boot from the
remaining harddisk(s).
I found that during boot (for some reason) the RAID device is not active
anymore and therefore not available within /dev/disk/by-uuid (what
causes the drop to the emergency shell).
A quickfix (to boot the system) would be, to re-activate the RAID device
(e.g. /dev/md0) from the emergency shell ...
mdadm --stop /dev/md0
mdadm --assemble /dev/md0
... and to exit the shell.
Nevertheless, it would be nice if the system would boot automatically
(as it is known to happend under wheezy) in order to be able to use e.g.
a spare disk for data synchronization.
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