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

[Dr Small]

Works good so far. I can't test out ssh yet, since I don't have openssh-server installed on my sisters system yet, but I will try that out soon.

Also, a small fix:
Back where you said:

Forward a xterm: ssh -Xfc -c blowfish user@server xterm

That should be a capital C after -Xfc. Example:

ssh -XfC -c blowfish

Because I was getting an error with c because of unknown cipher type.
Good job, this really makes things simpler yet

Great howto!

Edit:
A screenshot of icewm-session running through Xephyr at 800x600.
http://ubuntuforums.org/attachment.p...1&d=1195779441

Dr Small

[Dr Small]

Gtk-Xephyr

Allows you to run Xephyr in a Gtk environment, eliminating the use of starting it all with terminals. You must first download the script below, and give it executable permissions, and copy it to your /usr/bin directory.

Download from here:
Dr Small's Blog
Or Ubuntu Forums (1)
Chmod it with executable permissions:

chmod +x gtk-xephyr

Copy it to /usr/bin:

sudo cp gtk-xephyr /usr/bin

Open it with the Run Dialog (ALT + F2):

gtk-xephyr

Or make a launcher that points to that command.


I originally wrote this script, after disliking the fact that I needed to open multiple terminals to get this to work, and then Bodhi.Zazen fixed my bugs and made it better

You can find the original source of this from here:
http://php.8ez.com/drsmall/blog/?p=175

(1: If you downloaded the file from the attachment that I uploaded to Ubuntu Forums, please rename it to "gtk-xephyr" instead of "gtk-xephyr.sh". Ubuntu Forums required that I have a file type within their allow list.)


Dr Small

[nikoPSK]

I will have to try this tomorrow. thanks bodhi!

[adamorjames]

Looks awesome! Thanks.

[jimcooncat]

I had to add this to the beginning of the script:

unset SESSION_MANAGER

in order to avoid this error:

Another session manager is already running

[smartboyathome]

Dr Small, I have modified your script a bit to make it so you can enter your own screen resolution (instead of clicking on pre-defined ones). Here is the new script, in case anyone else wants it.

[scorp123]

Originally Posted by Dr Small Gtk-Xephyr ... Allows you to run Xephyr in a Gtk environment, eliminating the use of starting it all with terminals. I originally wrote this script, after disliking the fact that I needed to open multiple terminals to get this to work, and then Bodhi.Zazen fixed my bugs and made it better

Niiiiice!!

[Dratop]

Thanks for this great script for Xephyr. I still have a (noob?) question though : how do I specify in my xorg.conf file that I want the display associated to Xephyr to be outputted on a outer screen or video projector plugged to my laptop ? I both tried to configure this editing xorg.conf manually and using Nvidia X server settings but did not manage to find a solution.

Thanks in advance for your help.

[bodhi.zazen]

Originally Posted by Dratop Thanks for this great script for Xephyr. I still have a (noob?) question though : how do I specify in my xorg.conf file that I want the display associated to Xephyr to be outputted on a outer screen or video projector plugged to my laptop ? I both tried to configure this editing xorg.conf manually and using Nvidia X server settings but did not manage to find a solution. Thanks in advance for your help.

I am not sure what you are trying to do exactly, but Xephyr does not run the way you envision. It runs within an existing X session and is not configured through xorg.conf or nvidia-settings.

So you run xephyr on the same screen / x session that is already outputting to your video projector.