[Bug 1685193] Re: [17.04] systemd-udevd. Scripts started by a rule won't write to /var/log

[Dimitri John Ledkov]

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.

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https://bugs.launchpad.net/bugs/1685193

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

Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  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.

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