Debian - Troubleshooting
apt-update: There is no public key available for the following key ID
sudo apt-get install debian-archive-keyring sudo apt-key update
Upgrade Debian Linux system from Wheezy to Jessie stable release
Just extracted from linuxconfig.org:
apt-get update apt-get upgrade -y apt-get dist-upgrade -y sed -i 's/wheezy/jessie/g' /etc/apt/sources.list apt-get update apt-get upgrade -y apt-get dist-upgrade -y reboot