[arch-general] tmux/systemd: tmux user service exits on detach/logout

[David Runge]

Hey again,

On 2017-07-07 15:24:39 (+0200), David Runge wrote:
> I got a very strange behavior with tmux and systemd on my server and
> maybe someone knows a way around it.
> 
> The way I start tmux is as follows:
> Setting TMUX_TMPDIR to my user's XDG_RUNTIME_DIR and starting tmux in a
> systemd user service [1]. I do the same for other things, such as
> weechat [2]. They both use the same tmux.conf [3].
> Lingering is activated for my user, so the enabled user services will
> start with the system and stay running, even when it's disconnected...
> in theory (and this used to work very well, without a problem for
> years).
> 
> With some changes in systemd however, this seems to fail now, and I
> can't seem to find the reason why. Tmux just exits with "server lost"
> once I do a detach.
> At first I could only observe this behavior when I had a shared ssh
> session to the server (so I thought), that I then quit, or when I
> attached and detached the tmux session quickly.
> Now I'm getting this nearly every time I detach from the tmux session!
> 
> I tried several things by now, and it doesn't seem to make any
> difference:
> - using legacy cgroups [4], because of maybe being affected by this [5]
> - switching to single connections instead of shared connections for ssh
>   (lowered the amount of random tmux quits!)
> - using hardened kernel (just to try another one)
> - logging a tmux session, without getting any output, that would
>   explain, why this happens
> - crossing fingers (actually helps, because the bug seems completely
>   random ;/ )
> - using a system scope unit (tmux at username) [6], getting the same results
> - downgrading tmux to >=2.3 (no difference)
> - downgrading systemd to <=233-7 (seems to happen less frequently)
After a week of testing: tmux - in above mentioned setup - works much
more reliable with systemd 233-7.

Maybe any of the package maintainers can comment on it?

> For some awkward reason, it seems to have worked again for a short time,
> when Arch first switched to systemd 233 a few days back [6], but ever
> since it moved to systemd-stable [7], the problem is back (and even
> worse than before). Me thinking that might only be due to a "less
> frequent occurence" though.
So, in conclusion, the issue is most likely related to some changes
applied to the 233 branch in systemd-stable.

> [1] https://git.sleepmap.de/software/uenv.git/tree/user/tmux.service
> [2] https://git.sleepmap.de/software/uenv.git/tree/user/weechat.service
> [3] https://git.sleepmap.de/config/dotfiles.git/tree/.tmux.conf
> [4] https://www.freedesktop.org/software/systemd/man/systemd.html#systemd.legacy_systemd_cgroup_controller
> [5] https://github.com/systemd/systemd/issues/3388
> [6] https://wiki.archlinux.org/index.php/Tmux#Autostart_with_systemd
> [7] https://git.archlinux.org/svntogit/packages.git/commit/trunk?h=packages/systemd&id=e0ee38b0c90d0a0da7baad4f472f38dd451326a6
> [8] https://github.com/systemd/systemd-stable

Best,
David


-- 
https://sleepmap.de
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