[Bug 1171945] Re: Nested RAID levels aren't started after reboot

[tarantoga]

I am also affected by this regression. 
It looks like Wheezy disables udev for md and  uses an rc-script for assembling at boot; therefore it will not automatically assemble arrays after boot.
Trusty assembles real devices during and after boot, but seems to ignore virtual devices like /dev/md0.

So I added a new rule for virtual devices to the existing udev rules in
Trusty. I created /etc/udev/rules.d/85-mdadm.rules with this single line
rule:

SUBSYSTEM=="block", ACTION=="add|change",
ENV{ID_FS_TYPE}=="linux_raid_member", DEVPATH=="*/virtual/*",
RUN+="/sbin/mdadm --incremental $tempnode"

This rule (plus the existing ones) assemble my nested raid during boot
or any time later, but might not work for the root filesystem unless a
initramfs-tools/hooks script is created (not tested).

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https://bugs.launchpad.net/bugs/1171945

Title:
  Nested RAID levels aren't started after reboot

Status in “mdadm” package in Ubuntu:
  Confirmed

Bug description:
  If creating a RAID5+0 or similar, the lower RAID-5s are started, but
  not the RAID-0 on top of them. I've tested this with Lucid (works),
  Precise (does not work) and Raring (does not work). A successive mdadm
  --assemble --scan finds the new RAID-0 and allows it to be mounted. On
  Lucid, however, this is found automatically. Something funky with
  udev?

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: mdadm 3.2.5-1ubuntu0.2
  ProcVersionSignature: Ubuntu 3.2.0-40.64-generic-pae 3.2.40
  Uname: Linux 3.2.0-40-generic-pae i686
  ApportVersion: 2.0.1-0ubuntu17.2
  Architecture: i386
  CurrentDmesg: [   17.144075] eth0: no IPv6 routers present
  Date: Tue Apr 23 19:28:48 2013
  InstallationMedia: Ubuntu-Server 12.04.1 LTS "Precise Pangolin" - Release i386 (20120817.3)
  Lsusb: Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
  MachineType: Bochs Bochs
  MarkForUpload: True
  ProcEnviron:
   LANGUAGE=en_US:en
   TERM=xterm-color
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.2.0-40-generic-pae root=/dev/mapper/hostname-root ro
  SourcePackage: mdadm
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 01/01/2007
  dmi.bios.vendor: Bochs
  dmi.bios.version: Bochs
  dmi.chassis.type: 1
  dmi.chassis.vendor: Bochs
  dmi.modalias: dmi:bvnBochs:bvrBochs:bd01/01/2007:svnBochs:pnBochs:pvr:cvnBochs:ct1:cvr:
  dmi.product.name: Bochs
  dmi.sys.vendor: Bochs
  etc.blkid.tab: Error: [Errno 2] No such file or directory: '/etc/blkid.tab'

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