[Bug 136252] Re: [->UUIDudev] mdadm.conf w/o ARRAY lines but udev/mdadm not assembling arrays. (boot & hotplug fails)

[Steve Langasek]

Surbhi,

Sorry to be so long in reviewing this.  Some questions about the
proposed SRU diff:

  * While rebuilding the mapfile (mdadm -Ir), if appropriate name is not found
    in /dev/md, look for a name in mdadm.conf or the metadata.

There's no bug number for this change.  What issue is this fixing?  This
also doesn't appear to be in mdadm 3.1.4 - is the issue fixed
differently in later releases?

  * Allow an empty name rather than "unknown" for an array

What issue is this fixing (no bug number)?  Is there any chance of
regression from this change?

  * Identify md0 correctly - fixed typo (LP: #532960)

The SRU diff is 900 lines long... can you be more specific about which
line is the typo fix for this bug? :)

  * Resolve issues like mdadm -Ss; mdadm: unable to open /dev/md/r1: "No such
    file or directory"  
  * Report the correct superblock version.
  * Correct the logic for partitions in md devices. Use /sys/dev links to map
    major/minor to devnum in sysfs
  * Changed the open_mddev_devnum() to create_mddev_devnum() - as its really
    creating something in /dev. Also renamed for porting few changes from
    mdadm-3.4.1 to mdadm-2.6.7.x 
  * If two devices are added via -I, mdadm can get badly confused. Fixed this.

Again, not clear which changes map to which changelog entries, making it
very difficult to review this.  Maybe a bzr branch with individual
commits would make this easier to understand?

  * For autoassembly to work properly the initramfs should set the hostname.
    Copy the hostname binary and /etc/hostname in the initramfs so as to set
    the hostname at boot time. (LP: #136252)

It's surprising that initramfs-tools' init calls hostname, but doesn't
take any steps to make it available in the initramfs.  But I think this
is still the right place to do the copy since only when mdadm is used do
we need it in the initramfs.

  * At installation time hostname  will not be set before the array is
    created. Thus the uuid written on the root array created at Ubuntu
    installation time  will never correspond to that of the hostname. Due to
    this auto assembly will never work. Add support to use the machine name
    when the hostname is unspecified example at installation time.
    (LP: #136252) (LP: #532960) (LP: #330399)

None of the referenced bugs appear to discuss this happening at
installation time.  Can you explain why this would happen at install
time?  Isn't setting the host name one of the first things done in the
installer?  If that's not being done correctly, is there a bug to track
fixing this issue in the installer, too?  (Of course, we still need
mdadm to cope with any systems that were already installed this way.)

  * Fix the error " /dev/MKDEV not found"

>From what I see, this isn't an error, just a warning.  I don't think
this is appropriate to include in an SRU.

** Also affects: mdadm (Ubuntu Lucid)
   Importance: Undecided
       Status: New

** Also affects: mdadm (Ubuntu Maverick)
   Importance: Undecided
       Status: New

** Changed in: mdadm (Ubuntu Lucid)
       Status: New => In Progress

** Changed in: mdadm (Ubuntu Maverick)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/136252

Title:
  [->UUIDudev]  mdadm.conf w/o ARRAY lines but udev/mdadm not assembling
  arrays. (boot & hotplug fails)

Status in “mdadm” package in Ubuntu:
  In Progress
Status in “mdadm” source package in Lucid:
  In Progress
Status in “mdadm” source package in Maverick:
  In Progress

Bug description:
  Binary package hint: mdadm

  Hi,

  I could not boot from my /dev/md1 -> /dev/vg01/lv_root partition,
  because the initrd could not assemble the md0 and md1 devices. After
  reading mdadm.conf, I added these two lines to my config:

  # definitions of existing MD arrays
  ARRAY /dev/md0 devices=/dev/sda1,/dev/sdb1
  ARRAY /dev/md1 devices=/dev/sda5,/dev/sdb5

  and updated initramfs. After this, the system started normally. Before
  figuring out this, I used dpkg-reconfigure mdadm. So this seems to
  produce a non working config, which is copied to the initrd.

  Kind regards

  Christian

  -> However on hotplug systems mdadm.conf should not have to contain
  any references to specific DEVICEs, ARRAYs or HOMEHOST.

  -> We need to switch to a pure and secure UUID-based raid assembly.
  The boot up scripts already support and use UUIDs, but mdadm needs to
  be convinced (-> comment #42)