Linux - kill all processes by name (by pattern, pkill, killall)

Hello,

killing the process by name doesn't work for me, let's say I want to kill a firefox application running in Linux Ubuntu. It used to be fine via the killall command and now it doesn't work:

sudo killall firefox
firefox: no process found
sudo killall Firefox
Firefox: no process found

REPLY

So I was surprised that the killing process has to go through pkill:

sudo pkill -9 -f firefox

It works...