Run an X11 command from a different console

Question

On my Ubuntu 14.04 virtual machine compiz freezes often. I usually swtich to tty1 and kill the process, then switch back to tty7 and, if I can see a terminal window, I run compiz --replace & in it. But there are times when I don't see any terminal window, and right clicking on the desktop doesn't give any menu so I can open one and I have to restart lightdm service. This is work blocking.

My question is: how can I run compiz --replace & or any other command from a different tty on tty7?

I read this thread, but I don't know how to make tmux connect to a different tty on my machine, and the second one involves using the homebrew program. I also read this, but it involves having a daemon run on tt7 expecting for my commands. Isn't there any easier way to do this?

Answer 1

What matters is actually not what console you run the command from, but that you tell the program to connect to the still-existing X display. To do this, set the DISPLAY variable and restart Compiz from a standard terminal. Depending on your distribution and configuration, you may need to set XAUTHORITY as well. Switch to tty1 and type:

$ export DISPLAY=:0
$ compiz --replace &

The display may be different on your machine. Use who to find yours:

$ who
you tty1 [time] < This is you from tty1.
you :0 [time] (:0) < This is you from tty7.
 ^^ ^^
 This is your display on tty7

Note: you must be logged in as yourself on tty7 (graphically). Fortunately, when Compiz crashes, you are not disconnected from tty7 (even though you can't do much).

• Alex Burdusel: this doesn't seem to work or there is some other problem: $compiz (core) - Info: Loading plugin: core compiz (core) - Info: starting plugin: core than it hangs. All this in the tty1 terminal
• Gilles 'SO- stop being evil': @Burdu I wouldn't expect to see anything else in the terminal. The new instance of Compiz is now running. What is the effect on the GUI? Maybe you need to set DBUS_SESSION_BUS_ADDRESS as well.
• Alex Burdusel: compiz does not get reloaded in tty7; nothing changes.