On Thu, 25 Jun 2015 at 15:55 -0000, m.roth@5-cent.us wrote:
I've got a headless server running CentOS 7. I've got a user who wants to run some graphical software on it, and view using x forwarding. What I don't have clear is how to set this up. I've just installed xorg-x11-server-[Xorg, common]. I assume I need to run X, but I don't see running this in runlevel 5.
For (ssh based) X forwarding no X server needs to run on the server. I usually install the xorg-x11-xauth (necessary) and xterm (optional) rpms on all my servers in case X forwarding becomes necessary.
Then from your desktop (assuming Linux already running X) in a local xterm do something like:
ssh -Y remote-system
Once logged into the remote system you should now have a DISPLAY environment variable set which will tell any client applications how to connect back to the X server on your desktop.
For example, just run xterm on the remote server and a xterm window will pop up on your display. This is just an example. You could run xload or any other basic X application.
You can also run more complex applications. Many will run fine. Other applications may perform poorly (due to the X protocol chattiness: Firefox, etc). Other applications will have other issues (some gnome/kde/gtk applications make other assumptions about being on the same system as the window manager and try to use dbus and local system things).
Note about -X versus -Y with ssh:
-X enables basic X forwarding, It disables some X functionality making it "safer" to allow. -X also stops working after about 20 minutes (this is by design but not well documented). I only recently learned why it would stop working after pulling out the last of my hair.
-Y allows the full X protocol which might be a security risk. Some applications will only work with -Y. With this, remote X applications can grab keyboard interactions, grab passwords, put windows on top of other windows (obscuring security messages), etc.
For my own choice I use -Y (although I only enable it occasionally to specific systems).
Stuart