How to upgrade your Debian Wheezy to Jessie

Source

cp /etc/apt/sources.list{,.bak}
cat /etc/apt/sources.list
sed -i -e 's/ \(stable\|wheezy\)/ jessie/ig' /etc/apt/sources.list
apt-get update

apt-get --download-only dist-upgrade

apt-get dist-upgrade -y