top displays a list of processes, with the ones using the most CPU at the top.
$ top
top - 19:18:50 up 7:05, 1 user, load average: 3.29, 3.15, 2.95
Tasks: 285 total, 2 running, 218 sleeping, 0 stopped, 1 zombie
%Cpu(s): 23.3 us, 3.9 sy, 0.0 ni, 72.1 id, 0.1 wa, 0.0 hi, 0.6 si, 0.0 st
KiB Mem : 7926036 total, 234916 free, 3611080 used, 4080040 buff/cache
KiB Swap: 8142844 total, 8142844 free, 0 used. 3710668 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2034 hluo 20 0 3550056 265276 77060 R 54.1 3.3 37:54.94 cinnamon
989 root 20 0 550344 80488 59996 S 22.1 1.0 17:59.20 Xorg
19689 hluo 20 0 6022744 854960 79880 S 14.9 10.8 7:44.18 java
23603 hluo 20 0 999496 312492 45068 S 8.9 3.9 0:28.80 mintinstall
12538 hluo 20 0 551344 63408 35788 S 2.6 0.8 0:12.57 terminator
21272 hluo 20 0 983008 163760 85056 S 2.3 2.1 0:43.16 chrome
212 root -2 0 0 0 0 S 0.7 0.0 0:23.62 i915/signal:0
1843 hluo 20 0 2020032 15628 13160 S 0.7 0.2 0:48.59 winedevice.exe
21695 root 20 0 0 0 0 D 0.7 0.0 0:05.92 kworker/u8:0
410 root 20 0 0 0 0 S 0.3 0.0 0:01.82 jbd2/dm-1-8
893 root 20 0 503264 10876 8596 S 0.3 0.1 0:17.49 udisksd
The htop command is an improved top.
$ sudo apt-get install htop
The ps command lists running processes.
# lists all processes running on your system
$ ps -A
The pstree command is another way of visualizing processes. It displays them in tree format.
The kill command can kill a process, given its process ID.
$ kill PID
Given a search term, pgrep returns the process IDs that match it.
$ pgrep firefox
The pkill and killall commands can kill a process, given its name.
$ pkill firefox
$ killall firefox
The renice command changes the nice value of an already running process.
$ renice 19 PID
The xkill command is a way of easily killing graphical programs.
Select the window whose client you wish to kill with button 1....