Neil Brown wrote:
Two strategies for this situation are to stop mdmon after mounting the
rootfs, or just let it be terminated as a result of starting a new
instance from the final rootfs. The latter approach brings up the
question of how to communicate with the initramfs-mdmon-instance to make
sure we do not end up with two mdmon instances servicing the same
container. The proposed solution here is to switch to
abstract-namespace-sockets removing the need to drop a socket file.
What exactly do you mean by "abstract-namespace-sockets"??
Harald pointed me to this. It's the hack that udev uses for its control
socket [1]. You create a unix domain socket as usual but make the first
character of the file name a NULL byte.
I would much rather just down mdmon before pivot_root while everything
is read-only, and start it up again afterwards.
Problem 2: Discovery / Assembly
Several issues have forced dracut to punt on using mdadm -I. Instead
dracut copies mdadm.conf to the initramfs and uses mdadm -As after a
udevadm --settle. One low hanging issue is the fact that non-rootfs
arrays may only be partially assembled when dracut discovers and
switches to the final rootfs. Upon switching the in-progress map file
is lost. Moving /var/run/mdadm/map to /dev/.mdadm/map would appear to
solve this issue.
mdadm already uses /dev/.mdadm.map if /var/run is not writable. So is
this a solved problem, or do we need some other way to force mdadm not
to use /var/run too early.
So you are talking about commit cf3a3d78 [2]. I think the problem is
that /var/run/mdadm/map is writable in dracut so we never fall back to
/dev/.mdadm.map. Any reason to not make /dev/.mdadm.map the first
location to try?
Thanks,
Dan
[1]:
http://git.kernel.org/?p=linux/hotplug/udev.git;a=blob;f=libudev/libudev-ctrl.c;h=e47b2b66#l65
[2]: http://neil.brown.name/git?p=mdadm;a=commitdiff;h=cf3a3d78
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