Bug#825394: shim screen etc?

[Josh Triplett]

On Sat, 28 May 2016 14:49:41 -0400 Joey Hess <id at joeyh.name> wrote:
> Since the number of commands that start such a process is limited to
> screen/tmux/nohup, these could just be shimmed to do whatever's
> needed to let them keep running past logout.
> 
> Course it would make more sense to have a proper API that such programs
> can use themselves.
> 
> I have tried to develop such a shim:
> 
> #!/bin/sh
> cmd="$(basename "$0")"
> # hardcoded path so this shim can be in eg ~/bin/screen and run the real program
> systemd-run -q --scope --user /usr/bin/$cmd "$@"

I don't think systemd-run (or transient scopes in general, including
those created by the program natively) are the right solution to this
problem.  Instead, I think screen, tmux, a VNC server, or any other
command that runs a user session independent of the one it was called
from, should be invoking PAM to start a new session.  The PAM session
machinery would then run pam_systemd, which would register with logind.

PAM is the right way to start a new user session.  And in addition to
providing a solution that isn't systemd-specific, this also integrates
with any other session mechanism as well.  For instance, if you use PAM
to manage agents for SSH or similar, this solves the problem of screen
having SSH_AUTH_SOCK point to a stale SSH agent that died with the
session screen started from.

I would suggest adding PAM session support to screen.