[systemd-devel] Question about propagation of INVOCATION_ID and JOURNAL_STREAM env variables in Desktop Environments

[Andrei Borzenkov]

On 23.05.2024 09:18, Nop wrote:
>  From my terminal emulator that I start by clicking in the menu:
> echo "kitty: $(pidof kitty) - $INVOCATION_ID" && echo "plasmashell:
> $(pidof plasmashell) - $(sudo strings /proc/$(pidof
> plasmashell)/environ | grep INVOCATION_ID)"
> kitty: 4441 - e3ec804609094a139948a1887c90ac7a
> plasmashell: 857 - INVOCATION_ID=e3ec804609094a139948a1887c90ac7a
> 
> But indeed, looking at systemd-cgls, it is in its own scope:
> -.slice
> ├─user.slice
> │ └─user-1000.slice
> │   ├─user at 1000.service …
> │   │ ├─session.slice
> │   │ │ ├─plasma-plasmashell.service
> │   │ │ │ └─857 /usr/bin/plasmashell --no-respawn
> │   │ ├─app.slice
> │   │ │ ├─app-kitty-96877b039d10481298f59807a062a5c5.scope
> │   │ │ │ ├─4441 /usr/bin/kitty
> │   │ │ │ ├─4450 /bin/zsh
> │   │ │ │ ├─9810 systemd-cgls
> │   │ │ ├─app-steam-68615b37d4554dc8bcdce0bb903517bb.scope
> │   │ │ │ ├─2777 bash /home/ctxnop/.local/share/Steam/steam.sh
> │   │ │ └─app-chromium-185faea96ff5421b8ecfb0753298c32b.scope
> │   │ │   ├─2266 /usr/lib/chromium/chromium
> │   │ │   ├─2269 /usr/lib/chromium/chrome_crashpad_handler --monitor-self
> 
> Did not know about this, thank you. But it feels even more weird now:
> for P in 857 4441 4450 2777 2269; do echo -n "$P: " && tr '\0' '\n' <
> /proc/$P/environ | grep INV; done
> 857: INVOCATION_ID=e3ec804609094a139948a1887c90ac7a
> 4441: INVOCATION_ID=e3ec804609094a139948a1887c90ac7a
> 4450: INVOCATION_ID=e3ec804609094a139948a1887c90ac7a
> 2777: INVOCATION_ID=e3ec804609094a139948a1887c90ac7a
> 2269: INVOCATION_ID=e3ec804609094a139948a1887c90ac7a
> 

Looking here on GNOME I confirm the same behavior. Unless program 
explicitly handles INVOCATION_ID (or, I assume, any other environment 
variable set by systemd) they are inherited. I am "lucky" in that 
gnome-terminal does not propagate it, so I can use INVOCATION_ID to 
distinguish between being called from interactive shell and invoked as 
service. But I was about to add some launcher icons and they would 
certainly have the same issue as you described.

But everything started by gnome-shell inherits gnome-shell 
INVOCATION_ID. Everything started by gnome-session-binary inherits 
gnome-session-binary INVOCATION_ID. Etc ...

All that I am interested in is how I can distinguish between "it runs as 
part of interactive user session" or "it runs as part of systemd 
service". I do not see any way to do it.

It was so simple initially until someone got brilliant idea to misuse 
systemd user instance for session management ...