sudo halt

or

sudo shutdown -h

or

sudo init 0

Most distribution have firefox installed by default. But if it isn't you can try type these into the command line:

sudo apt[-get] install firefox

sudo yum install firefox

sudo dnf install firefox

sudo aptitude install firefox

sudo urpmi firefox

sudo installpkg firefox.tgz

sudo emerge firefox

sudo pacman -S firefox

The duration of SUDO-Q is 1800.0 seconds.

sudo will run a command with root privileges

Daisuke Sudo was born on 1977-04-25.