[17.04] systemd-udevd. Scripts started by a rule won't write to /var/log

[flux242]

this is rather weird problem but after upgrading to the 17.04 the pm-powersave script I start by a udev rule stopped working. After debuggin a bit I found a place that causes the error. In the /usr/lib/pm-utils/pm-functions there's the init_logfile function that called exec to redirect script's output to the /var/log/pm-powersave.log. And it fails to do so because root (under which the script is started) has no permission to write to anything under the /var/log/

Inside of that functions I added additional logging to prove that
1. the script is started under root
2. the file /var/log/pm-powersave.log exist and it has 644 permissions
3. the root can read from /var/log/*
4. /var permissions are 755, /var/log permissions are 775

If the script is started with 'sudo /usr/sbin/pm-powersave true' then it works!

So what could this be? Could the apparmor prevent udevd to write to /var/log ?

Temporary solution is to write to /tmp/pm-powersave.log

How to reproduce:
1. add the following rule to /etc/udev/rules.d/test.rules
SUBSYSTEM=="power_supply", ATTR{online}=="0", RUN+="/usr/sbin/testudev true"
SUBSYSTEM=="power_supply", ATTR{online}=="1", RUN+="/usr/sbin/testudev false"
2. create /usr/sbin/testudev script and make it executable
#!/usr/bin/env bash

logger "testudev: I'm: $(whoami)"
echo test >> /var/log/testudev.log

3. Plug and unplug the power plug. Check the syslog:
Apr 21 13:17:06 chrome root: testudev: I'm: root
Apr 21 13:17:06 chrome systemd-udevd[23333]: Process '/usr/sbin/testudev false' failed with exit code 1.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Dimitri John Ledkov (xnox)]

Yes, there are no permissions to write to /var/log, that is so far intentional.

Another question is why are you still using pmutils? My understanding is that Ubuntu no longer uses that at all, and uses systemd power management.

[flux242 (flux242)]

what are the intentions?

systemd power management huh? Which of these problems has already been solved since 15.10 then:

1. System doesn't react on the power supply plugged/unplugged events
2. Lid close events are handled by the systemd by default and not by the xfce4-power-manager
3. System doesn't execute pm-utils hooks on sleep/resume events, i.e when the power cord is unplugged all powertop's tunable should be in GOOD state. Are they?

[Dan Streetman (ddstreet)]

please reopen if this is still an issue