[Bug 645575] Re: udev rules for mdadm cause boot hangs and md array malfunctions

[Diego Morales]

I am not sure if they should be marked as duplicates, but see also
https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/1335642 .

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https://bugs.launchpad.net/bugs/645575

Title:
  udev rules for mdadm cause boot hangs and md array malfunctions

Status in udev package in Ubuntu:
  Confirmed

Bug description:
  Binary package hint: udev

  Hi,
  las week I upgraded ubuntu 9.10 to 10.04, and then installed 2 new hard drives and built a new md0 RAID1 array by means of mdadm, defining also a new mdadm.conf with just one line for md0, and a new entry in fstab for the mount point of md0.
  Upon reboot, the boot process stopped saying it couldn't find the device for this new mount point; /proc/mdstat listed this new strange "md_d0" array, inactive, with one of the two drives which were part of my md0.
  On further reboots, I noticed the drive "captured" this way by "md_d0" was randomly picked up between the two drives of md0.
  This thread here: http://osdir.com/ml/linux-raid/2009-08/msg00219.html directed my to the solution.
  So here's the content of my 85-mdadm.rules file, edited in order not to run mdadm --incremental for each and every array member found!!

  cat /lib/udev/rules.d/85-mdadm.rules 
  # This file causes block devices with Linux RAID (mdadm) signatures to
  # automatically cause mdadm to be run.
  # See udev(8) for syntax
  SUBSYSTEM=="block", ACTION=="add|change", ENV{ID_FS_TYPE}=="linux_raid*", \
  	RUN+="/sbin/mdadm --assemble --scan"
  #RUN+="/sbin/mdadm --incremental $env{DEVNAME}"
  #AMC100922: caused malfunctions on preconfigured arrays!!

  This way it works just fine.
  Don't know if this error could be related to the upgrade from 9.10 to 10.04, as I didn't have any md array on 9.10, and only defined it after the upgrade to 10.04.

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