Starting with the 0.7.7 release of the multipath tools, the multipath
udev rules always set a value in ENV{DM_MULTIPATH_DEVICE_PATH} for any
device that multipath scans. A value of 0 means that the device is not
claimed by multipath, and a value of 1 means that it is. Because of
this, udev rules that check ENV{DM_MULTIPATH_DEVICE_PATH}=="?*" will
always return True, and act as if every scanned device is claimed by
multipath. Checking ENV{DM_MULTIPATH_DEVICE_PATH}=="1" will work
correctly for both the old and new versions of the multipath tools.
The 69-dm-lvm-metad.rules set some udev env. variables that makes it
possible to detect the right time to activate LVM on MD. The MD is very
similar to DM during activation - it's usable only after proper device
activation - the CHANGE event. We need to make a difference between a
CHANGE event that comes from this activation and CHANGE event that is
the outcome of the WATCH udev rule (otherwise we'd end up with LVM
activation done on each CHANGE event - which is wrong).
So we need the udev databse to be persistent during pivot to root fs
even for MD devices.
Starting with commit 24a38bc1cb dracut
uses udev builtins but still depends on >=udev-166 in dracut.spec. This
patch makes dracut work with older udev again.
All credits go to Alexander Tsoy <alexander@tsoy.me>; see
https://bugs.gentoo.org/show_bug.cgi?id=437700
Benjamin Marzinski