[Bug 1825075] Re: (bionic) boot with degraded RAID array for non-root device enters emergency mode

[Trent Lloyd]

A degraded array used for the root filesystem DOES boot as expected on
Bionic. My guess is that during boot the "poor-mans mdadm-last-
resort at .timer" code from debian/initramfs/script.local-block is executed
where as with non-root devices that is not the case and it potentially
should use the actual mdadm-last-resort@ timer service?

Any filesystem in /etc/fstab not appearing results in an emergency mode
boot (I'm not sure that is always sensible, but never the less, you can
apparently specify 'nofail'). That leaves me guessing that the main
issue I imagine is that the device doesn't appear - the question is why
the timers/etc don't promote the degraded array to running after the
timeout and allow the system to boot. Does the emergency mode timeout
happen before it can do so?

** Changed in: mdadm (Ubuntu)
       Status: New => Confirmed

** Changed in: mdadm (Ubuntu)
   Importance: Undecided => High

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https://bugs.launchpad.net/bugs/1825075

Title:
  (bionic) boot with degraded RAID array for non-root device enters
  emergency mode

Status in mdadm package in Ubuntu:
  Confirmed

Bug description:
  When booting a Bionic system where an MDADM RAID device is degraded
  (e.g. 1 of 2 disks appear) and that device is for a non-root
  filesystem (e.g. /home) the boot enters emergency mode and the MD
  device stays inactive.

  This can be reproduced using the live server installation CD, 3 disks
  - 1 for /, and 2 for a software RAID which is then mounted to /home as
  ext4.

  After first boot, shutdown the system, remove one of the two RAID
  disks, and boot the system.

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