How to Xephyr ~ AKA Multiple, nested X sessions

[bodhi.zazen]

How to Xephyr



Click to enlarge

What is Xephyr ?

Xephyr is a X server that runs as a small window within your current X session.

What is it good for ?

There are multiple potential uses for Xephyr:

• Development. You can ssh into a chroot and forward X sessions.
• Forward X over ssh without VNC.

Example: Normally if you ssh -X you can forward x applications. This is not a problem if you are forwarding a single application from a single server. But if you forward multiple applications from multiple servers or a whole desktop, it gets messy (to say the least). You can start a new X session ( Virtual X ), but then you have to Ctl-Al-F7 and Ctrl-Alt-F8 between them.

1. Install Xephyr

sudo apt-get install xserver-xephyr

2. Start Xephyr

Xephyr -ac -screen 1280x1024 -br -reset -terminate 2> /dev/null :1 &

• The ":1" = your display (displays are numbered starting with 0)
• -ac = disable access control restrictions= allow you to forward X
• -screen 1280x1024 = screen size
• -br = black background
• -reset -terminate= Xephyr should automatically close when the last X client is killed, does not always work.
• 2> /dev/null redirects error messages.

3. Set your display (for X)

DISPLAY=:1.0

• Don't forget to set it back after you establish a ssh connection ( DISPLAY=0.0 )

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4. Forward single apps / separate window for each server.

Start Xephyr

Xephyr -ac -screen 1280x1024 -br -reset -terminate 2> /dev/null :1 &

Change your $Display

DISPLAY=:1.0

Forward a xterm:

ssh -XfC -c blowfish user@server xterm

• -X = forward X
• -f = puts your ssh session into the background
• -C = use compression -c blowfish = use blowfish (I am told this is the fastest)

Click to enlarge

• run "xfwm4" in the terminal for window decorations(substitute your window manager if you are not using xfce).
• xterm config file : http://www.xfce.org/various/Xresources.txt

Any X apps for that server will start in that window.


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5. Desktop:

Start Xephyr

Xephyr -ac -screen 1280x1024 -br -reset -terminate 2> /dev/null :2 &

2. ssh into the chroot/server

ssh -XfC -c blowfish user@server xfce4-session

• Substitute your window manager for "xfce4-session"

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Enjoy,

bodhi.zazen