Type=oneshot, as currently set in dracut's emergency service file,
causes an awkward situation if emergency mode is entered e.g. because
of a root device timeout, and the root device appears later because it
just has taken longer than the timeout. In that situation, my
expectation (backed by past positive experience) is that the user should
be able to simply exit the emergency shell and resume normal boot.
:/# systemctl status sysroot.mount
● sysroot.mount - /sysroot
Loaded: loaded (/proc/cmdline; bad; vendor preset: enabled)
Active: active (mounted) since Mon 2017-10-09 14:32:15 CEST; 16s ago
Where: /sysroot
What: /dev/mapper/3600601600a30200024fbbaf3f500e411-part5
Docs: man:fstab(5)
man:systemd-fstab-generator(8)
Process: 1873 ExecMount=/usr/bin/mount /dev/disk/by-uuid/63751805-6abc-46a3-a66f-427920dece4d /sysroot -o ro (code=exited, status=0/SUCCESS)
Tasks: 0 (limit: 512)
:/# systemctl list-jobs
JOB UNIT TYPE STATE
56 emergency.target start waiting
57 emergency.service start running
2 jobs listed.
:/# exit
logout
Failed to start default.target: Transaction is destructive.
(system keeps idling from this point on, user has no chance to
do anything).
This results from the combination of two effects:
1) initrd-root-fs.target sets "OnFailureJobMode=replace-irreversibly",
2) emergency.service's Type=oneshot causes the start jobs for both
emergency.service and emergency.target to persist while the user is in
the emergency shell.
When the shell is exited, systemd tries to isolate "initrd.target"
again, but this fails with "the transaction is destructive" error
because of the still pending jobs.
This patch fixes this by changing the Type of "emergency.service" from
"oneshot" to "idle".
Basic systemd functionality is in 00systemd now.
Switching root and the initrd.target is in 00systemd-initrd.
Dracut additions to the systemd initrd are in 98dracut-systemd.
Lidong Zhong