[Bug 1635049] Re: Boot fails with degraded mdadm raid

[Rüdiger Schernthaner]

It seems that this is still somehow broken with Xubuntu 17.04

I just tried mdadm within Xubuntu 17.04 in Virtualbox using the following setup:
1 virtual disk containing the OS.
2 virtual disks running as a RAID 1.
Whenever I disconnect one of the RAID disks, Xubuntu cannot boot.

I wrote the script shown here:
https://askubuntu.com/questions/789953/how-to-enable-degraded-raid1-boot-in-16-04lts
to the file /usr/share/initramfs-tools/scripts/local-top/mdadm
After that, Xubuntu can boot properly with the degraded RAID.

Is this the intended behaviour?
Thanks

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https://bugs.launchpad.net/bugs/1635049

Title:
  Boot fails with degraded mdadm raid

Status in mdadm package in Ubuntu:
  Fix Released
Status in mdadm source package in Xenial:
  Fix Released
Status in mdadm package in Debian:
  Fix Released

Bug description:
  [Impact]

   * Systems fail to boot in certain status of mdadm arrays, requiring
  manual recovery / array assembly

   * Backport of boot logic from yakkety

  [Test Case]

   * Install a system with RAID1 and two hard-drives and boot the system with array in-sync
   * Shutdown
   * Disconnect one of the drives and thus boot, unexpectedly, degraded
   * The boot should complete.
   * Shutdown, and boot again, expecting degraded state.
   * The boot should complete.
   * Shutdown, reconnect disconnected drive, and boot again.
   * The boot should complete, add the device to the array, the array should be resyncing, and results with system with array in-sync, just like at the beginning of the testcase.

  [Regression Potential]

   * Systems may continue to fail to boot degraded.

  [Other Info]

   * Original report

  mdadm does not attempt to start partial md devices (incremental
  assembly) during initramfs and can cause system to fail to initramfs
  prompt if rootfs on md.

  http://askubuntu.com/questions/789953/how-to-enable-degraded-raid1
  -boot-in-16-04lts

  Fixed in debian mdadm 3.4-2: https://bugs.debian.org/cgi-
  bin/bugreport.cgi?bug=784070

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