[systemd-devel] Questions about systemd's "root storage daemon" concept

[Martin Wilck]

On Mon, 2021-01-25 at 18:33 +0100, Lennart Poettering wrote:
> 
> Consider using IgnoreOnIsolate=.
> 

I fail to make this work. Installed this to the initrd (note the
ExecStop "command"):

[Unit]
Description=NVMe Event Monitor for Automatical Subsystem Connection
Documentation=man:nvme-monitor(1)
DefaultDependencies=false
Conflicts=shutdown.target
Requires=systemd-udevd-kernel.socket
After=systemd-udevd-kernel.socket
Before=sysinit.target systemd-udev-trigger.service nvmefc-boot-connections.service
RequiresMountsFor=/sys
IgnoreOnIsolate=true

[Service]
Type=simple
ExecStart=/usr/sbin/nvme monitor $NVME_MONITOR_OPTIONS
ExecStop=-/usr/bin/systemctl show -p IgnoreOnIsolate %N
KillMode=mixed

[Install]
WantedBy=sysinit.target

I verified (in a pre-pivot shell) that systemd had seen the
IgnoreOnIsolate property. But when initrd-switch-root.target is
isolated, the unit is cleanly stopped nonethless.

[  192.832127] dolin systemd[1]: initrd-switch-root.target: Trying to enqueue job initrd-switch-root.target/start/isolate
[  192.836697] dolin systemd[1]: nvme-monitor.service: Installed new job nvme-monitor.service/stop as 98
[  193.027182] dolin systemctl[3751]: IgnoreOnIsolate=yes
[  193.029124] dolin systemd[1]: nvme-monitor.service: Changed running -> stop-sigterm
[  193.029353] dolin nvme[768]: monitor_main_loop: monitor: exit signal received
[  193.029535] dolin systemd[1]: Stopping NVMe Event Monitor for Automatical Subsystem Connection...
[  193.065746] dolin systemd[1]: Child 768 (nvme) died (code=exited, status=0/SUCCESS)
[  193.065905] dolin systemd[1]: nvme-monitor.service: Child 768 belongs to nvme-monitor.service
[  193.066073] dolin systemd[1]: nvme-monitor.service: Main process exited, code=exited, status=0/SUCCESS
[  193.066241] dolin systemd[1]: nvme-monitor.service: Changed stop-sigterm -> dead
[  193.066403] dolin systemd[1]: nvme-monitor.service: Job nvme-monitor.service/stop finished, result=done
[  193.066571] dolin systemd[1]: Stopped NVMe Event Monitor for Automatical Subsystem Connection.
[  193.500010] dolin systemd[1]: initrd-switch-root.target: Job initrd-switch-root.target/start finished, result=done
[  193.500188] dolin systemd[1]: Reached target Switch Root.

After boot, the service actually remains running when isolating e.g. "rescue.target". But when switching root,
it doesn't work.

dolin:~/:[141]# systemctl show -p IgnoreOnIsolate nvme-monitor.service
IgnoreOnIsolate=yes

Tested only with systemd-234 so far. Any ideas what I'm getting wrong?

Martin