[Bug 1320402] Re: mdadm resyncs imsm raid in "Normal" state

[Martin Stjernholm]

Roger, many thanks for finding that. At first it looked like it wouldn't
work for me, but it turns out that both kernel >= 4.4.2 AND the script
fixes in comment #13 are necessary.

I have also tested and found that both fixes in #13 are still required:

-  /etc/init.d/mdadm: The mdmon pid is put into sendsigs.d at stop, but that's not enough -
   it has to happen already at start. MatthewHawn commented on that already in #13.

-  /etc/init.d/umountroot: The "mdadm --wait-clean --scan" kludge there is also still
   required. I note there's a script /etc/init.d/mdadm-waitidle that looks like it's
   supposed to do this, but it doesn't actually work. Probably some kind of sequencing
   problem, but I haven't dug into that.

So, the recipe to work around this bug in wily and xenial ought to be:

1.  Download and apply MatthewHawns patch in #13
    (https://launchpadlibrarian.net/191488884/mdadm.patch).

2.  Go to e.g. http://kernel.ubuntu.com/~kernel-ppa/mainline/ and pick a kernel >= 4.4.2
    (I've tested with 4.4.2 and the latest 4.4 atm, 4.4.17). Download the .debs for the
    architecture you need and install them using dpkg -i. See
    https://wiki.ubuntu.com/Kernel/MainlineBuilds for more detailed instructions.

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https://bugs.launchpad.net/bugs/1320402

Title:
   mdadm resyncs imsm raid in "Normal" state

Status in mdadm package in Ubuntu:
  Confirmed

Bug description:
  Got an imsm raid1 which I don't boot from. Whenever bios reports the
  raid as being in "Normal" state, mdadm starts a resync of it after
  boot. If a resync already is underway (bios reports it as being in
  "Verify" state), it continues where it left off.

  This appears to be very similar to a problem in Fedora:
  https://bugzilla.redhat.com/show_bug.cgi?id=753335 It's apparently
  fixed there for some time now. (The workaround mentioned in comment 41
  in that ticket doesn't work in Ubuntu, but I guess that's due to
  distro differences in initramfs and systemd.)

  Using mdadm 3.2.5-5ubuntu4 in a fresh Trusty install.

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