This article is outdated and may not work correctly for current operating systems or software.
Debian 9 codename Stretch is the latest stable release of Debian, which was released on June 17, 2017. In this tutorial, I am going to show you how to upgrade your Debian 8 (Jessie) server to the latest stable release.
Debian is an extremely stable operating system and upgrading from one release to another has always been easily performed. To be on the safe side, I strongly recommend that you make a full backup or at least backup any data or configuration information you can't afford to lose. The Vultr snapshot system can be used for easy backup and restore.
This is also a good time to check for broken packages:
sudo dpkg --audit
Update the system to the latest version.
apt update apt upgrade
Once upgraded, you will see the following output.
Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Make a copy of your original /etc/apt/source.list file.
cp /etc/apt/sources.list /etc/apt/sources.list-jessie
Now edit the file and replace the words jessie with stretch.
deb http://security.debian.org/ stretch/updates main contrib non-free deb-src http://security.debian.org/ stretch/updates main contrib non-free deb http://ftp.uk.debian.org/debian/ stretch-updates main contrib non-free deb-src http://ftp.uk.debian.org/debian/ stretch-updates main contrib non-free deb http://ftp.uk.debian.org/debian/ stretch main contrib non-free deb-src http://ftp.uk.debian.org/debian/ stretch main contrib non-free
Re-run system update and this time run
apt update apt upgrade apt dist-upgrade
After the upgrade is done, you can remove unnecessary packages.
Reboot the system.
After the system comes back up, login in and check the Debian version.
cat /etc/debian_version 9.1
... or check the kernel version.
uname -a Linux mydebian 4.9.0-3-amd64 #1 SMP Debian 4.9.30-2+deb9u2 (2017-06-26) x86_64 GNU/Linux
Upgrading a Debian system in place from Jessie to Stretch is an easy process, but keep in mind that before you decide to do it, you must check any possible third-party applications for compatibility issues.