Sometimes you have to kill them all
How do I force quit an application on Ubuntu 18.04 LTS?
When a program stops responding in Windows, most users know how to force it to quit by pressing Ctrl+Alt+Delete on their keyboard, selecting the Task Manager option, and closing the program from there. That approach isn’t entirely applicable to Linux distributions like Ubuntu, but that doesn’t mean you’re out of options when a program crashes.
On the contrary, there are quite a few ways to close a program on Ubuntu using CMD. If you're comfortable using the terminal, you can use commands like killall or xkill to force-close pesky programs, or you can use the System Monitor app instead.
While it’s easy enough to close an open process in Ubuntu using the terminal, beginners might not feel comfortable doing so. But an Ubuntu user doesn’t have to go anywhere near the terminal to force-quit a crashed application: you can use the System Monitor app instead.
