I'be been having issues lately trying to automatically remount an external USB drive that is mounted at boot from an fstab entry:
LABEL=data-ssd /opt/data-ssd ext4 defaults,nofail,users 0 2
I'm using systemd 244 and after some investigation I learned about the possibility to launch a systemd unit from a udev rule via ENV{SYSTEMD_WANTS} (see here https://github.com/systemd/systemd/issues/22589#issuecomment-1047940003 and https://github.com/systemd/systemd/pull/11373#issuecomment-594014841)
In particular the second suggestion is exactly what I need, but the only way I could make it work was launching a dummy.service that "Wants" the corresponding mount unit:
udev rule:
ACTION="" SUBSYSTEM=="block", KERNEL=="sd*", SUBSYSTEMS=="usb", ENV{DEVTYPE}=="partition", IMPORT{builtin}="blkid", ENV{ID_FS_TYPE}=="ext4", ENV{ID_FS_LABEL_ENC}=="data-ssd", ENV{SYSTEMD_WANTS}+="dummy.service"
dummy.service:
[Unit]
Description=Dummy service
Wants=opt-data\x2dssd.mount
[Service]
Type=simple
ExecStart=/bin/echo "I'm dummy"
[Install]
WantedBy=local-fs.target
Description=Dummy service
Wants=opt-data\x2dssd.mount
[Service]
Type=simple
ExecStart=/bin/echo "I'm dummy"
[Install]
WantedBy=local-fs.target
I also tested using ACTION!="remove" in the udev rule, but same result.
As I mentioned in the github issue before being redirected here, if I query with udevadm, ENV{SYSTEMD_WANTS} is printed out only with in the non-working case (.mount unit launched directly from the udev rule):
# udevadm info --query=property --path=/sys/class/block/sda1
[...]
SYSTEMD_WANTS=opt-data\x2dssd.mount
[...]
whereas it disappears if launching the dummy.service first.
# udevadm info --query=property --path=/sys/class/block/sda1
[...]
SYSTEMD_WANTS=opt-data\x2dssd.mount
[...]
whereas it disappears if launching the dummy.service first.
Thanks
