Upgrade Debian 9 Stretch to 10 Buster

This post describes the upgrade process to Debian 10 aka Buster which isn’t released yet.
Official release date is not announced for now but is to be expected in a second or third quarter of 2019.

For everyone who would like to profit from PHP 7.3 and other new and mostly stable software now,
can perform the upgrade already now.

Before you go on, make sure you have actual full backup of the system, which gets upgraded. Just to play save.

Also after upgrading approx. 10-12 in production state running Debian Instances to Buster,
I can share some deeper advices with you.
Upgrade of a MariaDB replication-setup upgrade was running without any issues.
I beamed sucessfully 10.1.37-MariaDB version to 10.3.12-MariaDB.

If your have any self hacked iptables/firewall scripts, make sure, you update the binary path, because all the iptables binaries have been moved away from /sbin to /usr/sbin.

If your instance is running letsencrypt certificates with auto-renewal;
the auto-renew functionality will break due of python version update. After Debian upgrade, make sure, you remove the /opt/eff.org directory and run the renewal script again.

Update the Debian stretch-installation to the actual patch level

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

and go on with the buster-upgrade process.

sed -i 's/stretch/buster/g' /etc/apt/sources.list
apt-get update
apt-get dist-upgrade

Perform a reboot and verify, that everything is running fine as before.

Update: 08.07.2019, original /etc/apt/sources.list

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