Handy commands

Command Description
sudo su login as root
sudo -H -s -u <user> login as user
adduser --ingroup <group> --disabled-password --disabled-login <user> create user and add it to a group
usermod -g <NewPrimaryGroupName> <UserName> Add user to a group (primary)
usermod -a -G <group> <user> Add user to a group (non-primary)
netstat -ntlp | grep LISTEN List open ports
getent passwd List all users
getent group List all groups
find / -name "<filename>" Find a file
df -h Show disk usage in human friendly way