[Bug 1526111] [NEW] RAID1 + LVM in 14.04.3 causes intermittent boot failure

[Cal Leeming]

Public bug reported:

This problem seems to be related to a timing bug within `udev`, and has been experienced by other users as seen here;
http://serverfault.com/questions/567579/boot-failure-with-root-on-md-raid1-lvm-udev-event-timing

Changing `/dev/md/0` to `/dev/md0` inside `/etc/mdadm/mdadm.conf` seems
to resolve the problem. However unless you apply this patch, the system
will intermittently fail to boot correctly, getting stuck here;

kernel: [    3.003506] md: bind<sda1>
kernel: [    3.007705] md/raid1:md0: active with 1 out of 1 mirrors
kernel: [    3.007768] md0: detected capacity change from 0 to 499972440064
kernel: [    3.047284]  md0: unknown partition table
kernel: [    3.124709] device-mapper: table: 252:0: linear: dm-linear: Device lookup failed
kernel: [    3.124759] device-mapper: ioctl: error adding target to table
kernel: [    3.125156] device-mapper: table: 252:1: linear: dm-linear: Device lookup failed
kernel: [    3.125196] device-mapper: ioctl: error adding target to table

There is also an example `/lib/udev/rules.d/` patch inside the thread I
posted above, which proposes to add a `sleep` statement into LVM udev
rules.

** Affects: udev (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: lvm mdadm raid

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https://bugs.launchpad.net/bugs/1526111

Title:
  RAID1 + LVM in 14.04.3 causes intermittent boot failure

Status in udev package in Ubuntu:
  New

Bug description:
  This problem seems to be related to a timing bug within `udev`, and has been experienced by other users as seen here;
  http://serverfault.com/questions/567579/boot-failure-with-root-on-md-raid1-lvm-udev-event-timing

  Changing `/dev/md/0` to `/dev/md0` inside `/etc/mdadm/mdadm.conf`
  seems to resolve the problem. However unless you apply this patch, the
  system will intermittently fail to boot correctly, getting stuck here;

  kernel: [    3.003506] md: bind<sda1>
  kernel: [    3.007705] md/raid1:md0: active with 1 out of 1 mirrors
  kernel: [    3.007768] md0: detected capacity change from 0 to 499972440064
  kernel: [    3.047284]  md0: unknown partition table
  kernel: [    3.124709] device-mapper: table: 252:0: linear: dm-linear: Device lookup failed
  kernel: [    3.124759] device-mapper: ioctl: error adding target to table
  kernel: [    3.125156] device-mapper: table: 252:1: linear: dm-linear: Device lookup failed
  kernel: [    3.125196] device-mapper: ioctl: error adding target to table

  There is also an example `/lib/udev/rules.d/` patch inside the thread
  I posted above, which proposes to add a `sleep` statement into LVM
  udev rules.

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