How to start an app with "Always On Top" set?

There is a more general solution, working with a EWMH/NetWM compatible X Window Manager (all commonly used wm are included).

The solution concerns the use of the wmctrl application (found in wmctrl package).

You can set the "on-top" property with

wmctrl -r "window title" -b add,above

There is, however, some work left to automate the process.

If you're using Compiz, you can go into CompizConfig Setting Manager, and enable the Windows Rules plugin, and then add something like class=Gnome-terminal under "Above" to make all Gnome Terminal windows Stick on Top. (You can click the + button and use the grab feature to figure out the class name for various applications if it's not obvious.)

Ubuntu 16.10

Make sure to install compiz-plugin.

There are two Methods in which you can archive this.

• This Method is permanent:

  Install Compiz and then compiz-plugin. Then go into CompizConfig Setting Manager, and enable the "Windows Rules" plug-in which is in "window management". Then go to the line "Above" and press the add button in front of it, And then the "Grab" button and then click on the window of the app which you want " always on top". Press OK.

• This Method is temporary:

  Press Alt+Tab and then T.