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Is it possible to reliable tell for a given Linux process if it was launched or is still supervised by an init.d script, Upstart or systemd ?
dronus
Posted 2015-05-16T11:04:32.117
Reputation: 1 482
Tell if a process is under systemd, init.d or Upstart control
Answers
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With systemd, you can find which systemd service a process belongs to by looking at the cgroup it is in.
For example:
$ ps -eo pid,comm,cgroup | grep dhclient
6476 dhclient 8:devices:/system.slice NetworkManager.service,1:name=systemd:/system.slice/NetworkManager.service
will tell you that the dhclient process is part of the NetworkManager.service, and is thus managed by systemd.
Whereas:
$ ps -eo pid,comm,cgroup | grep firefox
3302 firefox 8:devices:/user.slice,1:name=systemd:/user.slice/user-1000.slice/session-c2.scope
shows that this Firefox process is part of the session launched by the user with the UID 1000.
Processes launched by initscripts or Upstart jobs are indistinguishable from other manually launched background processes.
Siosm
Posted 2015-05-16T11:04:32.117
Reputation: 396
1You should be able to tell from its parent hierarchy. The easiest way is to use a system monitor in tree view. On Ubuntu 15.04 I find
ksysguardthe easiest to use, though you can also usegnome-system-monitor. If your Linux doesn't have these programs available, you can useps -eHl|lessand follow the tree from the program you're interested in. – AFH – 2015-05-16T14:30:25.027I don't think so. Looking at
pstreeat my system, most of the processes seem to have detached from their parent. There are only a few processes started by my desktop session, so most of the processes in the topmost level must have been started by some init deamon I guess. – dronus – 2015-05-16T15:41:05.627My
pstreeshows everything deriving fromsystemd(PID 1), includingupstart, which is well down the list. I get the same fromps -eHl. – AFH – 2015-05-16T16:39:21.610Because
systemdhas PID 1 (the topmost one), which is the only allowed top level process. This behavior of systemd is often criticised. So any process released from it's parent is parented bysystemd. If you use Upstart or init.d scripts on a systemd-free system, you see that most processes are just below init, despite the fact most of them where launched by Upstart or init.d scripts. On your system sporting systemd, you will see any process released by its parent below systemd, so you cannot tell who has launched the process in the first place that way. – dronus – 2015-05-16T18:31:56.743Sorry, I didn't know about this behaviour. Since most processes on 15.04 have
systemdas progenitor, this seems in keeping with what I had read, thatsystemdmostly replacedupstartin 15.04. By the way, just as an aside, I seem to have two top-level processes: because I run some KDE processes, there is alsokthreadd(PID 2), also with no parent, but with a lot of children. – AFH – 2015-05-16T20:03:25.467