LINUX: Useful commands

ps -aux|grep java //show processes containing 'java'
top                   //display processes list
passwd                //change current users password
passwd gus123         //change password user gus123
service iptables stop //stops firewall from running
chkconfig iptables off//firewall won't start on boot

tail -f textfile//turns a log file thats being
                //generated into a console
netstat -a      //shows port usage
touch <file>    //update timestamp of file
dd if=/dev/zero of=/dev/hda/ bs=512 count=1//wipe mbr
free -m               //check mem usage
du -x --block-size=1024K | sort -nr | head -10  
//10 biggest folders in current path
wc -l   gives linecount

Memory Usage Tools useful
http://www.ss64.com/bash/ also useful