Cloned OS LUN Fail to Boot

This document (000019656) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15 SP1
SUSE Linux Enterprise Server 12 SP5

Situation

When trying to boot from a cloned SAN LUN, system failing to boot and enter into dracut shell. Dracut is complaining about missing disk partition e.g. /boot or /boot/efi

Resolution

To fix this issue we need to use the dracut "--persistent-policy" option or "persistent_policy=" in dracut.conf.

For example:

cat >/etc/dracut.conf.d/policy.conf <<EOF
persistent_policy="by-uuid"
EOF

Also, make sure to use by-uuid device IDs in /etc/fstab.

Cause

By default, dracut prefers device-mapper names (aka disk WWIDs) as disk identifiers. That's not desirable in this specific use case. The new cloned LUN have a new WWID which is different than the original hardcoded WWID in initramfs. In other words, the default policy causes an error because the WWID of the cloned LUN is now different than before.

Additional Information

Default initramfs file uses device-mapper:

drwxr-xr-x   2 root     root            0 Jun 19 12:58 etc/systemd/system/dev-mapper-3600a0980383056547a5d50542f583267\\x2dpart1.device.d
-rw-r--r--   1 root     root           23 Jun 19 12:58 etc/systemd/system/dev-mapper-3600a0980383056547a5d50542f583267\\x2dpart1.device.d/timeout.conf
lrwxrwxrwx   1 root     root           63 Jun 19 12:58 etc/systemd/system/initrd.target.wants/dev-mapper-3600a0980383056547a5d50542f583267\\x2dpart1.device -> ../dev-mapper-3600a0980383056547a5d50542f583267\\x2dpart1.device
-rw-r--r--   1 root     root          140 Jun 19 12:58 lib/dracut/hooks/emergency/80-\\x2fdev\\x2fmapper\\x2f3600a0980383056547a5d50542f583267-part1.sh
-rw-r--r--   1 root     root           61 Jun 19 12:58 lib/dracut/hooks/initqueue/finished/devexists-\\x2fdev\\x2fmapper\\x2f3600a0980383056547a5d50542f583267-part1.sh

Using persistent-policy=by-uuid will generate initramfs with:

drwxr-xr-x   2 root     root            0 May 18 18:58 etc/systemd/system/dev-disk-by\\x2duuid-AD6B\\x2d2B1B.device.d
-rw-r--r--   1 root     root           23 May 18 18:58 etc/systemd/system/dev-disk-by\\x2duuid-AD6B\\x2d2B1B.device.d/timeout.conf
lrwxrwxrwx   1 root     root           42 May 18 18:58 etc/systemd/system/initrd.target.wants/dev-disk-by\\x2duuid-AD6B\\x2d2B1B.device -> ../dev-disk-by\\x2duuid-AD6B\\x2d2B1B.device
-rw-r--r--   1 root     root           92 May 18 18:58 lib/dracut/hooks/emergency/80-\\x2fdev\\x2fdisk\\x2fby-uuid\\x2fAD6B-2B1B.sh
-rw-r--r--   1 root     root           37 May 18 18:58 lib/dracut/hooks/initqueue/finished/devexists-\\x2fdev\\x2fdisk\\x2fby-uuid\\x2fAD6B-2B1B.sh

For more information check the dracut(8) or dracut.conf(5) man pages.

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