Your message dated Sat, 31 Jul 2021 23:49:15 +0200
with message-id <[email protected]>
and subject line Re: tmux is killed under gnome3 regardless of
KillUserProcesses=no
has caused the Debian Bug report #946645,
regarding KillUserProcesses=no disregarded for some cgroups
to be marked as done.
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--
946645: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=946645
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Package: systemd
Version: 244-3
Severity: normal
File: /usr/share/man/man5/logind.conf.5.gz
The documentation about KillUserProcesses claims that processes will be
left alive after user logout when set to "no", and specifically mentions
tmux as one application.
This is only correct under some circumstances (apparently related to
cgroups, but I'm not familiar enough with them to give good details).
The observed issue is as follows:
* In a fresh sid installation, start Gnome under X11 (Wayland not
tested).
* Alt+F2, xterm
* tmux
* Ensure you recognize the screen again later on
* Log out
* Log in back again, open xterm again
* tmux attach: "no sessions" -- the session was killed
In comparison, when `gnome-terminal` is used to start the tmux session,
it does survive the logout.
In drilling down to finding the difference at all (a process that seemed
very random to me in #945540, when I failed to take the terminal program
used into consideration), I noticed that the cgroups involved depended
on the terminal used: With xterm (or xfce4-terminal), the process seems
to be launched with cgroups pids, memory, name and "" in
/user.slice/user-$UID.slice/session-$SESSION.scope, whereas a surviving
tmux has its "", name and memory cgroups set to
/user.slice/user-$UID.slice/user@$UID.service/gnome-terminal-server.service
and the pids to /user.slice/user-$UID.slice/user@$UID.service.
It seems to me that processes under session-$SESSION.scope do get reaped
(whether deliberately killed by logind or somehow implicily by their
cgroups going away) at logout, and only those staretd from a program
that happens to switch cgroups survive.
Please change logind behavior to allow for all processes spawned in a
login session to survive, or if that is not possible, describe in the
KillUserProcesses which processes have a chance to survive.
For now, a usable workaround for me is to `systemd-run --user --scope
tmux` instead of tmux, but that's a workaround nobody should need to
use, especially as finding the need to do so usually involves having
lost one's tmux sessions over an X server crash before.
Thanks
chrysn
(Information down here relates to my production system where I've
reproduced the steps above with i3 instead of gnome).
-- System Information:
Debian Release: bullseye/sid
APT prefers unstable
APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 5.3.0-3-amd64 (SMP w/8 CPU cores)
Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8),
LANGUAGE=en_GB:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
Versions of packages systemd depends on:
ii adduser 3.118
ii libacl1 2.2.53-5
ii libapparmor1 2.13.3-7
ii libaudit1 1:2.8.5-2+b1
ii libblkid1 2.34-0.1
ii libc6 2.29-6
ii libcap2 1:2.27-1
ii libcryptsetup12 2:2.2.2-1
ii libgcrypt20 1.8.5-3
ii libgnutls30 3.6.10-5
ii libgpg-error0 1.36-7
ii libidn2-0 2.2.0-2
ii libip4tc2 1.8.4-1
ii libkmod2 26-3
ii liblz4-1 1.9.2-2
ii liblzma5 5.2.4-1+b1
ii libmount1 2.34-0.1
ii libpam0g 1.3.1-5
ii libpcre2-8-0 10.34-7
ii libseccomp2 2.4.2-2
ii libselinux1 2.9-3+b1
ii libsystemd0 244-3
ii mount 2.34-0.1
ii util-linux 2.34-0.1
Versions of packages systemd recommends:
ii dbus 1.12.16-2
Versions of packages systemd suggests:
ii policykit-1 0.105-26
pn systemd-container <none>
Versions of packages systemd is related to:
pn dracut <none>
ii initramfs-tools 0.135
ii udev 244-3
-- no debconf information
--- End Message ---
--- Begin Message ---
On Wed, 10 Mar 2021 21:18:34 +0100 Michael Biebl <[email protected]> wrote:
> Am 09.03.21 um 03:55 schrieb Russell Stuart:
> > I have similar observations to chrysn after starting and detaching a
> > tmux session with KillUserProcesses=no (the default):
> >
> > 1. If I do the process in Gnome-3 using gnome-terminal and I log out,
> > wait for a bit and log in (60 seconds is what I used), the detached
> > tmux session is gone.
> >
> > 2. If I do the process in Gnome-3 using gnome-terminal and I log out,
> > and log back in immediately, the tmux session usually survives.
> >
> > 3. If I Gnome-3 using gnome-terminal I run "loginctl enable-linger",
> > do the process above and log out and in, tmux session always
> > survives.
> >
> > 4. If started on a virtual console (crtl-alt-f3), and log out it
> > survives regardless of how long I want before logging in again,
> > and regardless of how many Gnome3 sessions are started and stopped
> > on the same machine.
> >
> > I guess a workaround would be to globally set "loginctl enable-linger"
> > for all logins but if there is such a setting I can't find it. (I
> > thought KillUserProcess=no was that setting, apparently not, but I'm
> > guessing that's because it isn't systemd doing this.) Alternatively if
> > someone can tell me how get Wayland version of KDE to run ...
>
> Laney, Simon, isn't this an issue in gnome-session? WDYT?
>
There was no further feedback, so I'm closing this issue.
Afaics, it is not related to KillUserProcesses=no
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