[PATCH v2] dracut-module-setup: Skip initrd-cleanup and initrd-parse-etc in kdump

[Lichen Liu]

When using multipath devices as the target for kdump, if user_friendly_name
is also specified, devices default to names like "mpath*", e.g., mpatha.
In dracut, we obtain a persistent device name via get_persistent_dev. However,
dracut currently believes using /dev/mapper/mpath* could cause issues, thus
alternatively names are used, here it's /dev/disk/by-uuid/<FS_UUID>.

During the kdump boot progress, the /dev/disk/by-uuid/<FS_UUID> will exist as
soon as one of the path devices exists, but it won't be usable by systemd,
since multipathd will claim that device as a path device. Then multipathd will
get stopped before it can create the multipath device.

Without user_friendly_name, /dev/mapper/<WWID> is considered a persistent
device name, avoiding the issue.

The exit of multipathd is due to two dependencies in the current dracut module
90multipath/multipathd.service, "Before=initrd-cleanup.service" and
"Conflicts=initrd-cleanup.service".

As per man 5 systemd.unit, if A.service has "Conflicts=B.service", starting
B.service will stop A.service.

This is useful during normal boot. However, we will never switch-root after
capturing vmcore in kdump.

We need to ensure that multipathd is not killed due to such dependency issue.
Without modifying multipathd.service, we add ConditionPathExists=!/proc/vmcore
to skip initrd-cleanup.service in kdump. This approach is beneficial as
it avoid the potential termination of other services that conflict with
initrd-cleanup.service. Also skip initrd-parse-etc.service as it will try to
start initrd-cleanup.service. Both of these services are used for switch root,
so they can be safely skipped in kdump.

Suggested-by: Benjamin Marzinski <bmarzins(a)redhat.com&gt;
Suggested-by: Dave Young <dyoung(a)redhat.com&gt;
Signed-off-by: Lichen Liu <lichliu(a)redhat.com&gt;
---
 dracut-module-setup.sh | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/dracut-module-setup.sh b/dracut-module-setup.sh
index 1dc88dc..0a901c2 100755
--- a/dracut-module-setup.sh
+++ b/dracut-module-setup.sh
@@ -1089,6 +1089,15 @@ install() {
         's/\(^[[:space:]]*reserved_memory[[:space:]]*=\)[[:space:]]*[[:digit:]]*/\1
1024/' \
         "${initdir}/etc/lvm/lvm.conf" &> /dev/null
 
+    # Skip initrd-cleanup.service and initrd-parse-etc.service becasue we don't
+    # need to switch root. Instead of removing them, we use ConditionPathExists
+    # to check if /proc/vmcore exists to determine if we are in kdump.
+    sed -i '/\[Unit\]/a ConditionPathExists=!\/proc\/vmcore' \
+        "${initdir}/${systemdsystemunitdir}/initrd-cleanup.service" &>
/dev/null
+
+    sed -i '/\[Unit\]/a ConditionPathExists=!\/proc\/vmcore' \
+        "${initdir}/${systemdsystemunitdir}/initrd-parse-etc.service" &>
/dev/null
+
     # Save more memory by dropping switch root capability
     dracut_no_switch_root
 }
-- 
2.43.0