This article is a summary of the activities described here: https://linuxiac.com/how-to-upgrade-to-debian-13-trixie-from-12-bookworm/

DISCLAIMER#

The steps here has been tested but I take no responsibility for your upgrade process. This post is only me sharing the experience following the referenced guide. This is a redacted version of the full article referenced above. For detailed information you are encouraged to visit that.

1 - Update your current version and weed out removed packages#

sudo apt update

sudo apt upgrade

sudo apt full-upgrade

sudo apt --purge autoremove

2 - Reboot#

sudo reboot

3 - Check your version#

cat /etc/debian_version

result: 12.11

4 - Check for non-debian packages and packages held for upgrade#

sudo apt list '?narrow(?installed, ?not(?origin(Debian)))'

sudo apt-mark showhold

result: Both checks should be empty. 

If checks are not empty - STOP! and read up on the necessary requirements to continue.

5 - Backup current files#

mkdir ~/apt

cp /etc/apt/sources.list ~/apt

cp -r /etc/apt/sources.list.d/ ~/apt

6 - Change version from bookworm to trixie#

sudo sed -i 's/bookworm/trixie/g' /etc/apt/sources.list

sudo sed -i 's/bookworm/trixie/g' /etc/apt/sources.list.d/*

7 - Fetch packages for trixie#

sudo apt update

8 - Do a minimal upgrade#

sudo apt upgrade --without-new-pkgs

Two dialogues will be displayed while upgrading

• Info listing upgrade changes: Press q to continue

• Dialogue asking for restarting services: Select “Yes”

9 - Do a full upgrade#

sudo apt full-upgrade

10 - Restart system#

sudo reboot

11 - Cleanup installation#

sudo apt --purge autoremove

sudo apt autoclean

12 - Check your version#

cat /etc/debian_version

result: 13.0