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XServer & X11

Default Port: 6000 (TCP)

Is it running

> echo $DISPLAY
:0

Available for connections ?

> telnet 127.0.0.1 6000
Trying 127.0.0.1...
telnet: Unable to connect to remote host: Connection refused

In case you need to check a more standard way...

netstat -ant | grep 6000
# OR
ss -tln | grep 6000
# OR
ss -tl | grep -i x11
# OR
ss -an | grep 6000

Yeah, that's right, i'm liking ss LOL

What security is enabled ?

https://www.stitson.com/pub/book_html/node72.html

> xhost
access control enabled, only authorized clients can connect
SI:localuser:rich

Allow user or device to use it

Tells XServer to allow access on ALL Local connections made via Unix Sockets.

Yes, the colon is needed! A User/Group can follow the colon to further restrict the access.

Only ever used this for providing a GUI to my machine from an app in a Container

All bets are off if port 6000 is not open

> xhost +local:
non-network local connections being added to access control list

Note you can add Hosts too

> xhost +localhost
localhost being added to access control list

FYI in case you're wondering... it will look like this

> xhost
access control enabled, only authorized clients can connect
INET:localhost
SI:localuser:rich

XServer not listening ?? Why ?

Well... security. So it is set that way for a reason... you can check your display manager or XServer directly (Xorg) to check if enabled/disabled.

https://wiki.netbsd.org/tutorials/x11/how_to_stop_x11_from_listening_on_port_6000/

If this security issue is not a valid convern then move ahead and enable it

X11 displays everything without encryption so anyone who can connect to the port can observe or more

Alternatives ? Yeah there are some

Check XServer

The unmagic word is nolisten

ps aux | grep X
root        1045  3.2  0.7 27375248 249068 tty7  Ssl+ 09:00  20:04 /usr/lib/xorg/Xorg -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
rich       60898  0.0  0.0   9092  2624 pts/0    S+   19:20   0:00 grep --color=auto X

Check Display Manager

The unmagic word is nolisten

> systemctl status display-manager
...
/usr/lib/xorg/Xorg -nolisten tcp :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch

Enable Listening on TCP (Mint -> Ubtuntu -> Debian)

I enabled on root as this is how i'm running Docker on my local

Once you're done restart your display manager

Enable on XServer

sudo vi /etc/X11/xinit/xserverrc

Remove the nolisten part

#!/bin/sh

#exec /usr/bin/X -nolisten tcp "$@"
exec /usr/bin/X "$@"

Enable on Display Manager: LightDM

sudo vi /etc/lightdm/lightdm.conf.d/70-linuxmint.conf

[SeatDefaults]
user-session=cinnamon
xserver-allow-tcp=true        # <-- Need this
xserver-command=X -listen tcp # <-- Need this

Restart your Display Manager

ALL your open Windows... go Bye-Bye 👋

sudo systemctl restart lightdm

What IS my Display Manager ?

There are several ways, one of these should work 😉

ALL

> systemctl status display-manager
● lightdm.service - Light Display Manager
...
/var/run/lightdm/root/:0

Minty

> inxi -Sxx
dm: LightDM

Linux XServer

> cat /etc/X11/default-display-manager
/usr/sbin/lightdm

How do i test XServer works ?

You probably already have the apps installed, but if you're in a Docker Container you likely don't

Install the apps

apt install -y x11-apps

Run some apps that use XServer:

  • xclock
  • xeyes <-- this one is great 🤣