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mv
Watchman
Joined: 20 Apr 2005
Posts: 6780
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 Posted: Sun Sep 07, 2014 7:19 am Post subject: systemd, X, and tmux (or screen) sessions: cgroups? |
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When playing with systemd, I observed an extremely annoying behaviour:
All detached tmux/screen sessions are killed (together with all tasks they are running) when the Xsession is killed (e.g. with Ctrl-Alt-Backspace).
This does not appear with openrc.
I conjecture the reason is that systemd starts the X session in a separate cgroup and killls the whole cgroup.
Is it possible to avoid this nonsense of systemd for the X session, e.g. by modifying the displaymanager.service correspondingly?
If it plays a role: I am using slim.service as displaymanager.service which has besides the ExecStart= value only Restart=on-failure. |
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franzf
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Joined: 29 Mar 2005
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mv
Watchman
Joined: 20 Apr 2005
Posts: 6780
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| Posted: Sun Sep 07, 2014 10:14 am Post subject: |
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Thanks; I got only different results with these keywords.
So it seems the systemd concept is indeed as broken as I conjectured.
Unfortunately, the hack around the systemd limitations is only a linked tarball in that thread which is not available anymore... Moreover, I am afraid that this works only for tmux sessions which you create as root, or can one exit a cgroup also as a user without special permission? |
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mv
Watchman
Joined: 20 Apr 2005
Posts: 6780
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| Posted: Mon Sep 15, 2014 3:09 pm Post subject: |
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The problem is still unsolved: I was not able to produce a libcgroup file which worked for me.
Moreover, I would like to avoid installation of libcgroup (e.g. gentoo's init.d-files are non-POSIX and thus do not work properly on openrc).
Actually, the problem even has sharpened: Even when logging in through ssh, it is not possible to keep a task running through tmux when systemd was booted.
It seems that this problem is yet another show-stopper for systemd... |
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mv
Watchman
Joined: 20 Apr 2005
Posts: 6780
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| Posted: Wed Sep 17, 2014 8:36 am Post subject: |
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As expected, the systemd maintainers reacted to the valid request (by somebody else) only with their usual mixture of arrogance and cluelessness:
| clueless guy wrote: | | And if you have a nohuped process that can lose the data if someone SIGKILLs it then you certainly deserve it |
So, in the first place you deserve a broken log if you use systemd as this is apparently still not able to produce atomc comits.
For me, this nonsense is probably the end of my systemd experiments: Systemd boycotts working software intentionally, so my init-system related software will in future boycott systemd. Perhaps I will not remove the currently existing systemd units, but I will certainly not do anything if they break, and nobody will receive corresponding support from me: Switch to a sane init-system written by people who are right in their mind if you want support from me.
Here is a "workaround" for the systemd insanity which I found despite the cooperation of systemd upstream.
As expected, it only works if you start screen/tmux/nohup as root, or you need to hack around with SUID/sudo - I found no secure solution for the latter which guarantees that only screen/tmux/nohup get these privileges without a password.
| /usr/bin/tmux-persistent wrote: | #!/bin/sh
printf '%s' "${$}" >|/sys/fs/cgroup/systemd/user.slice/tasks
exec tmux "${@}" |
As expected, all these things are not properly documented in systemd, so it is possible that this script has rather unexpected side effects and might turn out to be a security hole.
If you use systemd, you should not consider your system safe anyway: This would require maintaining by sensible people who have a proper concept and not working from one hack to another and declaring the working solutions as broken.
Edit: Fix typos.
Last edited by mv on Wed Sep 17, 2014 10:16 am; edited 1 time in total |
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Naib
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Joined: 21 May 2004
Posts: 6065
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| Posted: Wed Sep 17, 2014 9:58 am Post subject: |
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that is quiet bad but unfortunately not surprising...
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| Quote: | | Removed by Chiitoo |
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