http://www.webmin.com/deb.html
nano /etc/apt/sources.list
add the following:
deb http://download.webmin.com/download/repository sarge contrib
deb http://webmin.mirror.somersettechsolutions.co.uk/repository sarge contrib
save-exit
Fetch and install webmin GPG key with which the repository is signed, with the commands :
cd /root
wget http://www.webmin.com/jcameron-key.asc
apt-key add jcameron-key.asc
install webmin
apt-get update
apt-get install webmin
Wait for webmin to install – depending on your hardware, can take up to 30′.
Login to webmin as root, or as any user who can use sudo.