[Bug 120375] Re: cannot boot raid1 with only one disk

[Guilherme G. Piccoli]

This is a very old LP bug, but for completeness it worth mentioning here
that recently some patches were merged on initramfs-tools and
cryptsetup, that allow a good experience booting with LUKS-encrypted
rootfs on top of a degraded RAID1 array; for details, please check:
https://bugs.launchpad.net/ubuntu/+source/cryptsetup/+bug/1879980

Cheers,


Guilherme

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https://bugs.launchpad.net/bugs/120375

Title:
  cannot boot raid1 with only one disk

Status in initramfs-tools:
  Fix Released
Status in grub package in Ubuntu:
  Fix Released
Status in initramfs-tools package in Ubuntu:
  Fix Released
Status in mdadm package in Ubuntu:
  Fix Released
Status in grub source package in Hardy:
  Fix Released
Status in initramfs-tools source package in Hardy:
  Fix Released
Status in mdadm source package in Hardy:
  Fix Released

Bug description:
  The impact of the bug on users: Systems with root on a RAID array will
  not be able to boot if the array is degraded. Usrs affected by this
  will encounter an unusable system after a reboot (say, a kernel
  upgrade).

  Justification for backporting the fix to the stable release: Hardy is
  a LTS edition. It is expected that people will continue to use this
  version and not upgrade to Intrepid. People who have upgrade from
  Dapper LTS to Hardy LTS are affected too.

  TEST CASE
  Build a clean system with root on RAID, with Ubuntu 8.04 LTS. Degrade the root array. Reboot and shiver.

  A discussion of the regression potential of the patch and how users could get inadvertently effected. 
  - the only users that could be affected, as fas as  know, are the ones that already made a workaround and altered their system files accordingly.

  
  Binary package hint: mdadm

  if i unplug one hd from raid1 i cannot successfully boot because raid
  starts only if all disks are available through

  : "${MD_DEGRADED_ARGS:= --no-degraded}" in /usr/share/initramfs-
  tools/scripts/local-top/mdadm

  my workaround is:

  /etc/initramfs-tools/hooks/startdegradedraid

  #!/bin/sh
  #
  # Copyright <C2><A9> 2006 Martin F. Krafft <madduck at debian.org>
  # based on the scripts in the initramfs-tools package.
  # released under the terms of the Artistic Licence.
  #
  # $Id: hook 281 2006-12-08 08:14:44Z madduck $
  #

  set -eu

  PREREQ="udev"

  prereqs()
  {
          echo "$PREREQ"
  }

  case ${1:-} in
    prereqs)
      prereqs
      exit 0
      ;;
  esac

  MDADM=$(command -v mdadm 2>/dev/null) || :
  [ -x $MDADM ] || exit 0

  DESTCONFIG=$DESTDIR/conf/md.conf

  echo "MD_DEGRADED_ARGS=' '" >> $DESTCONFIG

  exit 0

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