[Bug 1335642] Re: mdadm runs into infinite loop and prevents initrd/initramfs phase to finish on boot

[Harald Staub]

Without really understanding, I tried to hack something and found the
following bits, use at your own risk. This is on a degraded mdadm RAID1
with the root filesystem as a LV.

The following procedure was found to help:

  * Interrupt grub and edit the linux command line.
  * Go to the end of the line that starts with "linux".
  * Append "break" to the line.
  * Press "Ctl-X" to boot. You will get a busybox prompt.
  * udevadm trigger --action=add
    * After that, "ls /dev/mapper" shows what is needed for the root parameter: HOST--vg-root
  * exit

The following procedure was found to make the above hack persistent:

  * Add new file /usr/share/initramfs-tools/scripts/init-premount
/10hack-raid-udev

#!/bin/sh
sleep 5
udevadm trigger --action=add
exit 0

  * update-initramfs -u

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https://bugs.launchpad.net/bugs/1335642

Title:
  mdadm runs into infinite loop and prevents initrd/initramfs phase to
  finish on boot

Status in “mdadm” package in Ubuntu:
  Confirmed

Bug description:
  Hi all,

  probably the issue is caused by changing the SATA-port where RAID
  disks were originally attached -- this is the only thing that happened
  before my Ubuntu 14.04 (kernel-3.13.0-27) became unbootable.

  During the boot the OS runs into infinite loop reporting from time to
  time these:

  incrementally starting raid arrays
  mdadm: Create user root not found
  mdadm: create group disk not found
  incrementally started raid arrays

  Since mdadm is in initrd image, I don't even know how to skip mdadm --
  workarounds are very welcome, please!

  For example, renaming /etc/mdadm/mdadm.conf in initrd image didn't
  help, mdadm then just repeats infinitely without group/user-related
  errors:

  incrementally starting raid arrays
  incrementally started raid arrays
  incrementally starting raid arrays
  incrementally started raid arrays
  ...

  Disks are successfully assembled into a RAID under LiveCD Ubuntu 13
  (yes , i have only old CD here)

  Why I consider this a bug? because my RAID-array is needed at
  application level, not on OS-level (e.g. it is not mounted as / or
  /boot). So, if one can't boot into OS it is a serious bug. Last but
  not least, I was never choosing to put mdadm into initramfs, so it is
  a decision taken by default that leads to not-bootable system...

  UPDATE1:
  in scripts/mdadm-functions of initrd image i see this:

  mountroot_fail()
  {
      message "Incrementally starting RAID arrays..."
      if mdadm --incremental --run --scan; then
          message "Incrementally started RAID arrays."
          return 0
      else        
          if mdadm --assemble --scan --run; then
              message "Assembled and started RAID arrays."
              return 0
          else
              message "Could not start RAID arrays in degraded mode."
          fi
      fi
      return 1
  }

  i tried 'mdadm --incremental --run --scan -c <path to
  etc/dmadm/dmadm.conf of initrd image> -v' and it exits silently
  without creating /dev/md/127 as I have expected.

  Whereas

  sudo mdadm --assemble --run --scan -c ./etc/mdadm/mdadm.conf -v

  Does the job. Is it an issue just of incremental mode?

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