VPS Customers running Debian 7 can upgrade to their latest OS version (currently Debian 8) with the following commands run as the root user:
apt-get update && apt-get upgrade
Then change any text of the word “wheezy” in /etc/apt/sources.list to “jessie” and run the above commands again, with more upgrade commands afterwards too (as root, preferably on your VPS Console (access to which we provide)):
apt-get update && apt-get upgrade && apt-get dist-upgrade
And answer Y to any prompts (eg: to restart services) or let it proceed with defaults.
Finally and before you reboot into your new upgraded kernel and system, it’s best to purge the obsoleted Debian 7 Packages, with the following commands run as root:
apt-get purge $(dpkg -l | awk '/^rc/ { print $2 }')
apt-get autoremove
FYI,
Richard.