Upgrade Debian 6 to 7

apt-get update -y && apt-get upgrade -y

echo "
deb http://mirrors.kernel.org/debian/ wheezy main
deb-src http://mirrors.kernel.org/debian/ wheezy main

deb http://security.debian.org/ wheezy/updates main
deb-src http://security.debian.org/ wheezy/updates main

# wheezy-updates, previously known as 'volatile'
deb http://mirrors.kernel.org/debian/ wheezy-updates main
deb-src http://mirrors.kernel.org/debian/ wheezy-updates main
" > /etc/apt/sources.list

To update the package list, enter:
apt-get update -y && apt-get upgrade -y && apt-get dist-upgrade -y

reboot

cat /etc/issue

backup:
tar zcpf /tmp/semua.tar.gz  --directory=/ --exclude=proc --exclude=sys --exclude=dev/pts --exclude=tmp .

restore:

tar zxpf /[folder]/semua.tar.gz  /