[systemd-devel] Activation environment(s)?

[Lennart Poettering]

On Fr, 12.01.24 18:16, Vladimir Kudrya (vladimir-csp at yandex.ru) wrote:

> On 08/01/2024 22.26, Simon McVittie wrote:
> > It is not possible to unset a variable in the dbus-daemon's activation
> > environment, or with `dbus-update-activation-environment`: that's an
> > API limitation in the org.freedesktop.DBus interface. I've thought about
> > adding an UnsetAndSetActivationEnvironment() that could do this.
> >
> > It *is* possible to unset a variable in the `systemd --user`
> > activation environment, with `systemctl --user unset-environment` or
> > the UnsetEnvironment() and UnsetAndSetEnvironment() D-Bus methods on the
> > systemd manager. If your distribution is using dbus-broker rather than
> > dbus-daemon, and if Mantas was correct to say that dbus-broker does not
> > have its own separate activation environment, then that should be enough
> > to affect all D-Bus session services. It will also affect all other
> > systemd user services.
>
> Thank you. I now recommend dbus-broker in my session manager's readme
> (https://github.com/Vladimir-csp/uwsm), and management of dbus activation
> environmentis now conditional on dbus unit true name not being
> dbus-broker.service.
>
> BTW, the whole reason I even decided to interact with dbus is rather
> aggressive session termination by systemd. It seems to send signals not only
> to existing processes in the session, but even to new ones which were
> spawned in response to those signals. This makes it impossible to fork a
> systemctl process to stop related user units.
>
> I solved this by interacting with dbus without spawning new processes, but,
> just for info, is there a proper way to fork something that survives for a
> bit in a session that is being terminated? With simple tools like `trap
> 'something' TERM HUP` in a shell? Or maybe there is some other more native
> way to bind a user level unit to a particular session scope?

When the goal is to shut down a service/session, then intend to give
guarantees that the shut down time is bounded: we first send SIGTERM,
and start a timeout. If by that timeout there are still processes left
we SIGKILL to put an end to things. If we'd somehow distinguish
new/old processes then we couldn't put the boundary on the shutdown
process...

So no, this does not exist. You can fork if you want, but it won't add
time to the time-out.

Lennart

--
Lennart Poettering, Berlin