upgrade to debian 8

Upgrade wheezy ( debian 7 ) to jessie ( debian 8 )

adjust /etc/apt/sources.list to something like this
deb http://ftp.gr.debian.org/debian/ jessie main non-free contrib
deb-src http://ftp.gr.debian.org/debian/ jessie main non-free contrib

deb http://security.debian.org/ jessie/updates main contrib non-free
deb-src http://security.debian.org/ jessie/updates main contrib non-free

# jessie-updates, previously known as 'volatile'
deb http://ftp.gr.debian.org/debian/ jessie-updates main contrib non-free
deb-src http://ftp.gr.debian.org/debian/ jessie-updates main contrib non-free

Most likely, NTUA 's debian mirror in athens is not your closest mirror.
You may want to use another debian mirror.

upon adjusting /etc/apt/sources.list update apt index
# apt-get update


and upgrade all the packages and the base system
# apt-get upgrade

or
# apt-get dist-upgrade


You will have to quit a few informative pagers and answer a few questions, but everything works out fine.





upgrade to debian 8