Finding and Killing a Process in GNOME

There are a few different ways to find and kill a process in Linux. Using the GNOME interface, you can call up the System Monitor (similar to the one on Windows XP) under System->Administration->System Monitor. Under the Processes tab, right clicking on a process will give you a variety of options: stop/end/kill/continue the process, change the priority (nice), display a memory map (pmap) and display open files (lsof -p <procID>).

Embedding the system monitor in a desktop panel is useful for constantly monitoring the system and quickly determining if and where there is a problem. Do this with Right Click on Panel->Add to Panel...->System & Hardware->System Monitor->Add. The display provides graphs of Processor, Memory, Network, Swap Space, Hard disk and Load activity (not quite sure what load is, perhaps some metric computed from all the others? I don't use it, personally).

On the command line, list processes with the ps command or ps -e for all users' processes. Pipe that through grep (i.e., ps -e | grep firefox) to find a process ID of the target process (if you know the exact name of the program, you can also use pidof firefox-bin). To kill a process, use the kill <procID> command (with the -9 flag if you want to kill it unconditionally). Alternatively, if the process uses a gui, you can use xkill to merely click on the gui to kill the corresponding process. There is also killall if you want to kill by process table name (i.e. killall firefox-bin).

pgrep and pkill are two very useful utilities, especially for dealing with processes with long command line invocations. pgrep -fl -u danny "ruby.*asdf" will print the process id and name of every process owned by danny whose command line invocation matches the passed in regular expression. The -f argument tells it to match against the full command line invocation instead of just the process name. pkill -fu dannyc "ruby.*asdf" will kill those same processes (for the life of me, I can't seem to coax similar behavior out of killall).

The top command provides an integrated way of finding and killing a process on the command line. If the process-to-be-killed is using a lot of system resources, it will appear towards the top of the display. Hit k and then the process ID to kill the process. Top comes with a lot of other functionality -- hit h for help.

UPDATE: I recommend using htop instead of top, which is top with less suck. It has lots of good features like color, mouse support, a more responsive interface, a tree-based process view, etc.