More X-Window Tips and Tricks

Starting X on other virtual terminals

With Linux, you are not limited to starting X-window only once. You may open up another virtual terminal and start another instance of X-window. Remember though that running two instances will use up a lot of memory.

As we saw in previous lessons, to switch to another virtual terminal, press:

CTRL + ALT + F2 (or F3 up to F6)

Then login as another user and type:

startx -- :1

You can switch between instances of X-Window by typing:

CTRL + ALT + F7 and
CTRL + ALT + F8

Using the X-Window programs from another computer

This is the thing I love to show people from the MS Windows world. I point to the computer across the room and then say: "Now I am going to start the browser from that system and make it appear here." You don't need to be David Copperfield to perform this magic. You only need X-window running on one and installed on the other. You also need a means of logging in to the other computer. And here's one more thing. The computer doesn't even need to be in the same room. It can be in a different room in a different building on a different continent. Providing your bandwidth is good enough, you can start a program on a computer 5000 kilometers away and use it on your desktop.

There are two ways to do this. One is not secure and probably should only be used on a local network, if at all. The second one is very secure and can be used for trans-oceanic X-window sessions.

If you have the remote login device telnet and the telnet server installed on the machines, you can use this fairly safely in a local network. For example, if your workstation is called 'amos' and the other machine is called 'andy' and you want to use a program on 'andy', sitting at 'amos', you would type:

xhost +andy

Then with telnet, login into 'amos' (telnet> open amos)

Then, type:

DISPLAY=amos:0.0
then
export DISPLAY

Now you can type the name of any program you want to run that you know is on 'andy'. Remember though, as I mentioned, telnet is insecure. This are better ways of doing this. You should never do this if you're working over a public network, like the Internet.

Remote X sessions with OpenSSH

Open SSH stands for Open Secure Shell. That's just what it is. A secure shell for logging in at other computers in a secure manner. What goes over the network is encrypted and your security is not compromised. Most major distributions will offer this and it is normally installed by default. You may have to specifically install the OpenSSH server which you need to have to for this to work on your local network. Using X on another machine, also known as X forwarding is usually disabled by default so you may have to edit one file to get this to work locally. If you're doing this across oceans or continents the configuration will depend on the remote machine. As long as you have a OpenSSH client and an account on the other machine, you can do this.

As I mentioned, if you want to do this locally. Here's what you have to do. Let's use our 'amos' and 'andy' example again. You're sitting at your workstation called 'amos'. Make sure you have OpenSSH server on installed on 'andy' and have created a user account there. On 'andy' you need to login as 'root' and make sure that there is a line in a file called 'sshd_config', usually located in /etc/ssh that says X11Forwarding yes. If this says X11Forwarding no than you need to change it to yes. Then you need to restart the OpenSSH server. The easiest way is to look for its PID by typing: ps ax | grep sshd and killing it's PID number. Then type: sshd to start the server again.

Then, from 'amos' just connect to 'andy' via SSH, like so:

ssh -l [yourusername] andy

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