Can't acces to Xauthority for X11VNC (Ubuntu 20.04)

Question

I'm trying to implement X11VNC on Ubuntu 20.04 but it's been frustrating. I need to use command way, the goal is to keep it on a systemd service.

As I know Ubuntu is using Xorg for the moment. Running ps wwwwaux | grep auth I get this:

gdm 3530 0.0 2.4 211180 50128 tty1 Sl+ 10:41 0:01 /usr/lib/xorg/Xorg vt1 -displayfd 3 -auth /run/user/125/gdm/Xauthority -background none -noreset -keeptty -verbose 3

admin-r+ 4700 0.2 2.7 216112 55220 tty2 Sl+ 11:58 0:02 /usr/lib/xorg/Xorg vt2 -displayfd 3 -auth /run/user/1000/gdm/Xauthority -background none -noreset -keeptty -verbose 3

So it should be correct to run the X11VNC server like this when user is not logged in (forget security pls):

x11vnc -xkb -noxrecord -noxfixes -noxdamage -forever -rfbport 11226 -auth /run/user/125/gdm/Xauthority -display :0

And like this when it's logged in:

x11vnc -xkb -noxrecord -noxfixes -noxdamage -forever -rfbport 11226 -auth /run/user/1000/gdm/Xauthority -display :0

Well, it works good on GDM, but not when the user is logged in.

• Tried with root and user profile of course.
• UUIDs checked of course.

Also tried with the directive GDM conf file WaylandEnable=false commented and without comment. When comment it, it works running this when the user is logged in:

x11vnc -xkb -noxrecord -noxfixes -noxdamage -forever -rfbport 11226 -display :0

But not works in GDM. If I comment it, it works on GDM from root with:

x11vnc -xkb -noxrecord -noxfixes -noxdamage -forever -rfbport 11226 -auth /run/user/125/gdm/Xauthority -display :0

So I don't get a solution for everything. I'm now out of ideas. LightDM is not a solution, cause we want to use GDM3.

Any response will be highly appreciated.

Regards.

Answer 1

The problem was the display. As lightdm only uses one display (:0), GDM raises a display for each user, so this should be correct and works for me:

x11vnc -xkb -noxrecord -noxfixes -noxdamage -forever -rfbport 11226 -auth /run/user/1000/gdm/Xauthority -display :1

Answer 2

I've had similar problems. I couldn't login to Ubuntu on the boot screen. and finally came up with a workaround script to fix X11VNC's issues while using the default GDM3 on Ubuntu 21. I wish X11VNC would fix this.

Use this as a setup script to configure your X11VNC after installing x11vnc.

    #!/bin/bash
if [ -z "$1" ]; then echo "Please pass the password you would like to use as an argument to this script"; exit 1 ; else echo "Good start.going ahead."; fi
apt update && apt install tmux -y
password=$1
passwordfile='/etc/x11vnc.pass'
servicefile='/etc/systemd/system/x11vnc.service'
timerfile='/etc/systemd/system/x11vnc.timer'
script='/usr/bin/startxvnc'
apt-get update
apt-get install x11vnc net-tools -y
x11vnc -storepasswd $password $passwordfile
cat >$servicefile <<'EOT'
[Unit]
Description="x11vnc"
Requires=display-manager.service
[Service]
Type=simple
#Environment=XAUTHORITY=$(ps aux | grep -o -E "(-auth)(.)(Xauth)[a-zA-Z]+")
#ExecStart=tmux new -s gj -d '/usr/bin/x11vnc $(ps aux | grep -o -E "(-auth)(.)(Xauth)[a-zA-Z]+") -display :0 -rfbauth /etc/x11vnc.pass -shared -forever'
#ExecStartPre=tmux new -s x11vnc -d
ExecStart=bash -c /usr/bin/startxvnc
#ExecStop=tmux kill-session -t x11vnc
Restart=on-failure
RestartSec=2
[Install]
WantedBy=graphical.target
WantedBy=multi-user.target
EOT
cat >$timerfile <<'EOT'
Unit]
Description=Wait for some time before running X11VNC
[Timer]
OnBootSec=5sec
[Install]
WantedBy=timers.target
EOT
cat >$script <<'EOT'
#!/bin/bash
getxauths()
{
xauths=()
ps aux | grep -o -E "(-auth)(.*)(Xauth)[a-zA-Z]+" | (while IFS= read -r xauth
do
xauths+=("$xauth")
done
printf "%s\n" "${xauths[@]}" | sort -u
) }
getpname()
{
#psp=$(ps -p $(lsof -t -i:5900) -o command)
psp=$(cat /proc/$(lsof -t -i:$1)/cmdline)
echo $psp
}
killproc()
{
pkill -9 $(lsof -t -i:$1)
echo "Killed by port $1"
}
starttmux()
{
xauth=$1
        tmux new -s $xauth -d
        tmux send-keys -t $xauth:0 "for (( ; ; )) ; do sleep 3s; ((disp ^= 1)) ; /usr/bin/x11vnc -display :$disp -auth $xauth -rfbauth /etc/x11vnc.pass -shared -forever ; done" Enter
}
#echo $(getpname)
start() {
for (( ; ; )) ; do
#echo $psp
xauths=$(getxauths)
for xauth in $xauths ; do
xauth="$xauth" | xargs
if [[ ${xauth} != "-auth" ]];then
            unset tsessions
            tsessions=($(tmux list-sessions -F '#{session_name}'))
echo "tessions is " ${tsessions[@]}
echo "xauth is " ${xauth}
        if [[ ! " ${tsessions[@]} " =~ " ${xauth} " ]]; then
starttmux $xauth
psp=$(getpname 5900)
echo $psp | grep -E -o "(-auth)(.)(Xauth)[a-zA-Z]+" | (while IFS= read -r xold
do
sessionname=$(echo ${xold#"-auth"} | xargs)
#tmux kill-session -t "$sessionname"
        if [[ ! " ${tsessions[@]} " =~ " ${xauth} " ]]; then
            if [[ $psp == "user/125"*  ]] ; then killproc 5900 ; tmux kill-session -t "$sessionname"  ; echo "session name is $sessionname" ;
             fi ; else starttmux $xauth ; sleep 30s ; fi
done)
    fi


fi
done
sleep 3s
done
}
start
EOT
chmod u+x $script
sed -i -e 's/WaylandEnable=true/WaylandEnable=false/g' /etc/gdm3/custom.conf 
sed -i -e 's/#WaylandEnable=false/WaylandEnable=false/g' /etc/gdm3/custom.conf
systemctl daemon-reload
systemctl enable x11vnc.timer
systemctl stop x11vnc.service
systemctl disable x11vnc.service
systemctl restart x11vnc.timer