Running multiple X11 sessions

For testing out Window managers, or developing applications it's sometimes useful to run more than one X11 Window session. Normally you'd do that by setting up X to run on another virtual terminal, but thats a bit awkward to use, and only works if you're physically in front of the machine. Instead you could run nested X11 sessions.

XNest allows you to start a new X11 session inside your current one, running completely seperate from it.

It's very useful for testing out Window Managers, as you can only have one window manager running at a time.

xnest is usually installed when you setup the X11 window system on Debian machines, but if it's not you can get it by running the following command as root:

apt-get install xnest

Usage is very simple:

Xnest -ac :2

This will create a new window which has the DISPLAY string set to ":2". (The -ac flag allows you to connect to it, and is important).

Once this is done you can run commands that will display inside that by adding "-display :2" to their command line, such as:

xterm -display :2

This will give you an xterm running inside your new X11 environment.

To run a new window manager run:

/etc/alternatives/x-window-manager -display :2

This will give you your default window manager in the new session, which you can use to execute programs, etc.

If you wish to test out a new window manager, such as xfce you can do that by running as root:

apt-get install xfce4

Then:

Xnest -ac :22 &
export DISPLAY=:22
xfce4-session &

This sets up a new X11 session running as ":22", and then starts a copy of the xfce environment inside it.

If you like it you can set this up as your primary window manager, if not you can just remove it..