distrobox-enter should terminate child processes when the terminal is closed

[1player]

A bit of a weird one... I've been trying to figure out why host-spawn, and its children, do not terminate on my machine when I close a terminal window (1player/host-spawn#27). In theory, when you close a terminal window, a SIGHUP is sent to the controlling process, so anything that was running is terminated cleanly, which is what everyone expects.

This doesn't happen with distrobox-enter. This script calls podman exec, which ignores SIGHUP (probably because it is/was originally intended to run containers in the background), so any process running inside the container is never terminated and runs indefinitely in the background.

Steps to reproduce

• Enter a distrobox container in a terminal window
• Run a long running process (sleep infinity)
• Close the terminal window
• Notice that the long running process is still running

Expected behaviour (how it works normally)

• Open a terminal window on the host
• Run a long running process (sleep infinity)
• Close the terminal window
• Notice that the long running process has been terminated

This discrepancy is because SIGHUP, sent by the kernel when the pty closes, so that the foreground process can terminate, is being ignored by podman exec. I'm unsure what's the best approach here.

[1player]

See also: containers/podman#19944

[89luca89]

I confirm this happens with podman and docker, it does not happen with lilipod

This is because the spawned process by exec, is child of either conmon on podman, and dockerd on docker
So the exiting "exec" command does not correctly forward it to the spawned process

This does not happen on lilipod where the "exec" command is indeed the father of the spawned process

Not sure what I can do, and if it's correct to be fixed on my side

[1player]

toolbox has been having the same issue, linking all related discussions here for cross-reference:

containers/toolbox#1207

containers/toolbox#1204

[1player]

After some back and forth, it does seem to be a distrobox bug. Basically, podman forwards SIGHUPs it receives. But the problem is distrobox-enter basically runs a podman exec -i sh, making that sh process PID 1, which by default ignores all signals (see StackOverflow link). A work around would be to call a helper program/script that traps the SIGHUPs that podman forwards, and kill the children (or the entire process group)

See also: https://stackoverflow.com/a/60537655

[89luca89]

After some back and forth, it does seem to be a distrobox bug. Basically, podman forwards SIGHUPs it receives. But the problem is distrobox-enter basically runs a podman exec -i sh, making that sh process PID 1, which by default ignores all signals (see StackOverflow link). A work around would be to call a helper program/script that traps the SIGHUPs that podman forwards, and kill the children (or the entire process group)

See also: https://stackoverflow.com/a/60537655

I'm not sure if that's what you're referring to, but PID1 is distrobox-init , not the bash/shell spawned by enter
So that won't be closed if you exit the terminal, because that's supposed to be stopped only by a distrobox-stop or podman stop

Doing a quick experiment with distrobox-enter, the main process is only forwarded a SIGTERM when closing the terminal:

the child bash -l process (in this case) is spawned and controlled by conmon and not by distrobox-enter

So I'm not sure how I can forward this SIGHUP to the bash -l if that's not actually spawned by my script