[Bug 964052] Re: mdadm: created as /dev/md0, becomes /dev/md127 after reboot.

[Tony Middleton]

I have seen this behaviour a number of times on Ubuntu and Debian.

After you create the array you need to update mdadm.conf.  However, this
is not enough as you also need to update the version in initrd.img.
This might happen automatically if you subsequently do some updates.  I
find the easiest way to force it is to call

dpkg-reconfigure mdadm

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Title:
  mdadm: created as /dev/md0, becomes /dev/md127 after reboot.

Status in mdadm package in Ubuntu:
  Confirmed

Bug description:
  -- lsb_release -rd
  Description:    Ubuntu precise (development branch)
  Release:        12.04
  --

  -- apt-cache policy mdadm
  mdadm:
    Installed: 3.2.3-2ubuntu1
    Candidate: 3.2.3-2ubuntu1
    Version table:
   *** 3.2.3-2ubuntu1 0
          500 http://us.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages
          100 /var/lib/dpkg/status
  --

  -- Environment
  Ubuntu 12.04 Server Edition 64bit (installed from the 20120323 daily ISO)
  Installed into a guest running on VirtualBox 4.1.10, hosted on Windows 7.
  Disk configuration: 
  1 SATA controller
  1 20GB HDD (used at / mount point)
  5x 512MB HDD (used to simulate RAID5 array)
  --

  -- What action I took
  On an untouched installation, I install mdadm, and attempt to create a RAID5 array with this command:

  sudo mdadm --create /dev/md0 --level=5 --raid-devices=5 /dev/sdb
  /dev/sdc /dev/sdd /dev/sde /dev/sdf

  After confirming that I wanted to create the array, mdadm reported success.  I initialized a file system on it, mounted it, and created a simple text file containing 'Hello World' on it.  Then, I reboot.
  --

  -- What I expected to happen
  mdadm would reassemble the array at boot time as /dev/md0.
  --

  -- What happened instead
  mdadm reassemled the array at boot time as /dev/md127.
  --

  It took a great deal if hunting around to discover that the array had
  actually been assembled.  I forget what command I issued that finally
  tipped me off to the existence of the assembled array, but running
  'sudo mdadm --detail /dev/md127' confirmed that it was the array I had
  just built.  I mounted the array and viewed the contents of the text
  file to confirm.

  This did not occur when I built my array on my test and production
  servers running Ubuntu 10.04 Server 64bit, so I am calling this new
  and unexpected behavior, and filing it as a bug.

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: mdadm 3.2.3-2ubuntu1
  ProcVersionSignature: Ubuntu 3.2.0-20.32-generic 3.2.12
  Uname: Linux 3.2.0-20-generic x86_64
  ApportVersion: 1.95-0ubuntu1
  Architecture: amd64
  CurrentDmesg:
   
  Date: Sat Mar 24 11:05:07 2012
  InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Alpha amd64 (20120323)
  MDadmExamine.dev.sda: Error: command ['/sbin/mdadm', '-E', '/dev/sda'] failed with exit code 1: mdadm: cannot open /dev/sda: Permission denied
  MDadmExamine.dev.sda1: Error: command ['/sbin/mdadm', '-E', '/dev/sda1'] failed with exit code 1: mdadm: cannot open /dev/sda1: Permission denied
  MDadmExamine.dev.sda2: Error: command ['/sbin/mdadm', '-E', '/dev/sda2'] failed with exit code 1: mdadm: cannot open /dev/sda2: Permission denied
  MDadmExamine.dev.sda5: Error: command ['/sbin/mdadm', '-E', '/dev/sda5'] failed with exit code 1: mdadm: cannot open /dev/sda5: Permission denied
  MDadmExamine.dev.sdb: Error: command ['/sbin/mdadm', '-E', '/dev/sdb'] failed with exit code 1: mdadm: cannot open /dev/sdb: Permission denied
  MDadmExamine.dev.sdc: Error: command ['/sbin/mdadm', '-E', '/dev/sdc'] failed with exit code 1: mdadm: cannot open /dev/sdc: Permission denied
  MDadmExamine.dev.sdd: Error: command ['/sbin/mdadm', '-E', '/dev/sdd'] failed with exit code 1: mdadm: cannot open /dev/sdd: Permission denied
  MDadmExamine.dev.sde: Error: command ['/sbin/mdadm', '-E', '/dev/sde'] failed with exit code 1: mdadm: cannot open /dev/sde: Permission denied
  MDadmExamine.dev.sdf: Error: command ['/sbin/mdadm', '-E', '/dev/sdf'] failed with exit code 1: mdadm: cannot open /dev/sdf: Permission denied
  MachineType: innotek GmbH VirtualBox
  ProcEnviron:
   TERM=xterm
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.2.0-20-generic root=/dev/mapper/hostname-root ro
  SourcePackage: mdadm
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 12/01/2006
  dmi.bios.vendor: innotek GmbH
  dmi.bios.version: VirtualBox
  dmi.modalias: dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:
  dmi.product.name: VirtualBox
  dmi.product.version: 1.2
  dmi.sys.vendor: innotek GmbH
  etc.blkid.tab: Error: [Errno 2] No such file or directory: '/etc/blkid.tab'

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