Flush RAM and buffers
free && sync && echo 3 > /proc/sys/vm/drop_caches && free
Get process who are consuming RAM
ps aux --sort -rss
Get process tree
ps axjf
Kill process by name
pkill firefox
killall -15 lighttpd
Kill process by pid
kill -15 1464
Get remaining disk space
df -H
Get disk space used by a folder
du -s -h /usr