loadYOURSELF

#apt-get install openssh-server openssh-client

      # gpg –keyserver subkeys.pgp.net –recv KEY
# gpg –export –armor KEY | sudo apt-key add -                    # Ubuntu supported packages (packages, GPG key: 437D05B5)
deb http://archive.ubuntu.com/ubuntu dapper main restricted
deb http://archive.ubuntu.com/ubuntu dapper-updates main restricted
deb http://security.ubuntu.com/ubuntu dapper-security main restricted
# Ubuntu supported packages (sources, GPG key: 437D05B5)
deb-src http://archive.ubuntu.com/ubuntu dapper main restricted
deb-src http://archive.ubuntu.com/ubuntu dapper-updates main restricted
deb-src http://security.ubuntu.com/ubuntu dapper-security main restricted
# Ubuntu community supported packages (packages, GPG key: 437D05B5)
deb http://archive.ubuntu.com/ubuntu dapper universe multiverse
deb http://archive.ubuntu.com/ubuntu dapper-updates universe multiverse
deb http://security.ubuntu.com/ubuntu dapper-security universe multiverse
# Ubuntu community supported packages (sources, GPG key: 437D05B5)
deb-src http://archive.ubuntu.com/ubuntu dapper universe multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper-updates universe multiverse
deb-src http://security.ubuntu.com/ubuntu dapper-security universe multiverse
# Ubuntu backports project (packages, GPG key: 437D05B5)
deb http://archive.ubuntu.com/ubuntu dapper-backports main restricted universe multiverse
# Ubuntu backports project (sources, GPG key: 437D05B5)
deb-src http://archive.ubuntu.com/ubuntu dapper-backports main restricted universe multiverse

if apt-get update command results with this error

you can fix this with apt-key update

or

with

gpg –keyserver wwwkeys.eu.pgp.net –recv-keys AB1233123423ada123131

# apt-key add /root/.gnupg/pubring.gpg

# apt-get update …