GNURoot in Action–Upgrade from wheezy to Jessie

• Fully Upgrade current System

# apt-get update
# apt-get upgrade
# apt-get dist-upgrade

• Upgrade to Debian Jessie

# sed -i 's/wheezy/jessie/g' /etc/apt/sources.list

# apt-get update
# apt-get upgrade
# apt-get dist-upgrade

• Check it

root@localhost:~# cat /etc/os-release 
PRETTY_NAME="Debian GNU/Linux 8 (jessie)"
NAME="Debian GNU/Linux"
VERSION_ID="8"
VERSION="8 (jessie)"
ID=debian
HOME_URL="http://www.debian.org/"
SUPPORT_URL="http://www.debian.org/support/"
BUG_REPORT_URL="https://bugs.debian.org/"

btw, I recommend you upgrade to Debian Jessie before install nginx and PHP, and in order to easily do the upgrade job, I recommend you install SSH server first.