Debian Jessie to Buster (Raspberry)

jessie_to_buster.sh

# Do not run as a script
# Commands should be run manually step by step

# Check current version
lsb_release  -a

# Look for partially installed packages
sudo dpkg --audit

# Check for hold packages (should be empty)
sudo dpkg --get-selections | grep hold

# Upgrade packages version 
sudo apt-get update && sudo apt-get upgrade

# Install & removes extra packages solving conflicts
sudo apt-get dist-upgrade

# Change apt sources to stretch (from jessie)
sudo sed -i /deb/s/jessie/stretch/g /etc/apt/sources.list
sudo sed -i /deb/s/jessie/stretch/g /etc/apt/sources.list.d/*.list

# Update packages list
sudo apt-get update

# Upgrade packages version (stretch)
sudo apt-get upgrade
sudo apt-get dist-upgrade

# If you have additional conflicts with other packages, you need to solve them here
# e.g. I had some with fail2ban version so disabled it until the end.

# Clean
sudo apt-get autoremove
sudo apt-get autoclean

# Reboot
sudo reboot

# Show system release (should be Stretch)
lsb_release -a

# Upgrade stretch packages
sudo apt-get update && sudo apt-get upgrade -y

# Look for partially installed packages
dpkg --audit

# List packages in hold state (should be empty)
apt-mark showhold

# Change apt sources to buster (from stretch)
sudo sed -i 's/stretch/buster/g' /etc/apt/sources.list
sudo sed -i 's/stretch/buster/g' /etc/apt/sources.list.d/raspi.list 

# Look for old missing sources (should be empty too)
grep -lnr stretch /etc/apt
grep -lnr jessie /etc/apt

# Remove apt-listchanges
sudo apt-get remove apt-listchanges

# Upgrade packages to buster 
sudo apt-get update && sudo apt full-upgrade -y

# Clean
sudo apt-get autoremove -y && sudo apt-get autoclean

# Fix any broken/previous error
sudo apt --fix-broken install

# Check system release (should be Buster)
lsb_release -a

# Reboot & enjoy Buster
sudo reboot