After exiting "ssh-agent -s" and "applet.py" processes remain lingering. Proposed solution.

I have found out that each new remote desktop spawns a "ssh-agent -s" and a system-config-printer "applet.py" process which will remain once the desktop session is closed, preventing the systemd session from exiting normally. This happens at least when using lightdm, I haven't tried with other display managers.

The problem with applet.py is known upstream and is WONTFIX. It's been reported to happen with sddm, kdm and lightdm.

I propose the following solution for lightdm:

1) Edit /etc/lightdm/lightdm.conf and put this line under section [Seat:*] session-cleanup-script=/etc/lightdm/session-cleanup-script.sh

2) Create the file /etc/lightdm/session-cleanup-script.sh with the following content

#!/bin/bash
#exec >/tmp/lightdm-cleanup-script.log 2>&1 #uncomment this line to log any error output when the script is run

# kill lingering applet.py and "ssh-agent -s" processes

ALL_SESSION_ID=$(loginctl list-sessions|cut -c -7|grep -E "[0-9]+$")
for SESSION_ID in $ALL_SESSION_ID; do
        SESSION_SCOPE=$(systemd-cgls --no-pager -u session-$SESSION_ID.scope)
        LEADER_PID=$(loginctl -p Leader --value show-session $SESSION_ID)
        # get the pids using grep -noE to extract strings of numbers prepended by line_number':'. There can be more than one hit per line so use uniq to keep just the first result. uniq comparison works only up to 99 lines.
        SESSION_PIDS=$(echo "$SESSION_SCOPE"|grep -noE "[1-9][0-9]*"|uniq -w 2|cut -f 2 -d ':')
        # if leader PID doesn't exist anymore
        if [[ ! " ${SESSION_PIDS} " =~ [[:space:]]${LEADER_PID}[[:space:]] ]]; then
                PIDS=$(echo "$SESSION_SCOPE"|grep -E "(applet.py)|(ssh-agent -s)"|grep -noE "[1-9][0-9]*"|uniq -w 2|cut -f 2 -d ':')
                # kill processes
                for PID in $PIDS; do kill $PID; done
        fi
done

3) Make the script executable with chmod +x /etc/lightdm/session-cleanup-script.sh

4) Restart lightdm systemctl restart lightdm

Explanation: I haven't managed to get the current systemd session scope for the lightdm process launching the session-cleanup script ("loginctl session-status" returns error), so I resorted to kill all "ssh-agent -s" and "applet.py" processes on all systemd session scopes where the leader has already been killed. This script will be run each time the desktop session is terminated. A bit blunt but works fine.

gitbls / RPiVNCHowTo

After exiting "ssh-agent -s" and "applet.py" processes remain lingering. Proposed solution. #14