Upgrade Debian 8 Jessie To Debian 9 Stretch

Upgrading server on a remote location is not safe unless you have KVM access. I did many Debian 8 to Debian 9 upgrade on remote server with out probem. On one server, network card name chaned from eth0 to new enp4s0 format. I had to access the server using KVM and fix network configuration by editing /etc/network/interfaces

First you need to upgrade all software on your server to latest Debian 8

apt update && apt upgrade -y && apt dist-upgrade -y

Now replace content of /etc/apt/sources.list file with following

vi /etc/apt/sources.list

Add

deb http://cloudfront.debian.net/debian/ stretch main non-free contrib
deb-src http://cloudfront.debian.net/debian/ stretch main non-free contrib

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

Update the software again with

apt update && apt upgrade -y && apt dist-upgrade -y

It can take some time for the upgrade to finish. Once update complete, you can check with lsb_release -a command, you will see

Remove unused packages with command

apt autoremove -y

At this stage, server stil use old debian 8 kernal.

root@v2m2:~# uname -r
3.16.0-6-amd64
root@v2m2:~# 

To boot to new Debian 9 kernal, reboot the server with

reboot

After reboot, you will see new kernal.

Now Debian 10 is available. See How to upgrade Debian 9 to Debian 10