From Debian 12 Bookworm to Debian 13 Trixie Upgrading Process

With the official release of Debian 13 “Trixie” on August 9, 2025, the Debian Project has ushered in the next generation of the world’s most stable Linux distribution, bringing refreshed packages, updated desktops, enhanced architecture support, and numerous under-the-hood improvements. At the same time, Debian 12 “Bookworm” — which was first released in June 2023 — is approaching its end of security support from the main Debian Security Team around June 10, 2026 before transitioning into Long Term Support (LTS). This makes planning your upgrade timely and ensure continued access to timely security updates and fixes.

🚨 Important: Back Up Before You Upgrade

Before attempting a release upgrade from Debian 12 (Bookworm) to Debian 13 (Trixie), make sure you:

Back up all important data — user files, databases, etc.
Back up system configuration (e.g., /etc, firewall rules).
Back up package metadata (including dpkg --get-selections and APT state).

A major release upgrade has strong tooling, but unexpected issues can still occur, especially with custom configs or 3rd-party software. Also read the official Debian upgrading guide here:
👉 https://www.debian.org/releases/trixie/release-notes/upgrading.en.html

Always rely on the official release documentation as your primary source of truth. This guide is intended to help with a standard in-place upgrade from Debian 12 “Bookworm” → Debian 13 “Trixie” for systems that are essentially vanilla Debian, also NOT a desktop environment, possibly with a small number of well-maintained third-party repositories that have Trixie-compatible packages. This guide includes a find-based approach to update third-party sources, but always cross-check that those repos support Trixie before proceeding.

Note that Debian only officially supports upgrading directly from Debian 12 to Debian 13 — if you are on Debian 11 “Bullseye” or older, you need to first upgrade to Debian 12 (Bookworm) using the Bookworm release notes and tools, and then you can upgrade from Debian 12 to Debian 13. Attempting to skip this intermediate step is not supported by Debian and can lead to an inconsistent system.

Warning: Performing distribution upgrades over SSH usually works, but it is strongly recommended to have local or out-of-band access (such as console, KVM, or IPMI) available. In rare cases, issues during or after the upgrade may prevent the system from booting correctly or bring down network connectivity, making remote access impossible.

🧑‍💻 Step-by-Step Upgrade Instructions for Debian 12 Bookworm

🔹1. Check Disk Space and Current Version

Ensure you have sufficient free disk space (e.g., 5 GiB or more conservative estimate):

#!/bin/bash
df -h

If needed, run:

#!/bin/bash
sudo apt clean
sudo apt autoremove # remove unused packages

Confirm you are on Debian 12:

#!/bin/bash
cat /etc/os-release #or cat /etc/debian_version or lsb_release -a
#Note down the Linux kernel version too
uname -mrs

🔹2. Ensure Bookworm Is Fully Up-to-Date

Before moving to Trixie, bring your current system fully current:

#!/bin/bash
sudo apt update
sudo apt upgrade -y
sudo apt autoremove -y

If this pulls in a new kernel, reboot now:

#!/bin/bash
sudo reboot

🔹3. Start a Safe tmux Session

Start tmux so the upgrade continues even if your SSH session disconnects:

#!/bin/bash
sudo apt install tmux -y
tmux

Re-attach later if needed:

#!/bin/bash
tmux ls
tmux attach # [Number]

🔹4. Update APT Sources to Trixie

Edit repository references to use trixie instead of bookworm.

Option 1 — Simple find+sed

# Debian repo:
sudo sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
# Change all 3rd-party repos (If found)
sudo find /etc/apt/sources.list.d -type f -exec sed -i 's/bookworm/trixie/g' {} \;

Option 2 — Modernized deb822 format (recommended later)

After the upgrade, convert sources to the new deb822 format:

#!/bin/bash
sudo apt modernize-sources

Debian 13 officially encourages deb822 source files stored under /etc/apt/sources.list.d/ for just one debian.sources file.

🔹5. Refresh Package Lists

#!/bin/bash
sudo apt update # Ensue no error occurred

If you see GPG key errors (rare but possible), install updated keyrings:

#!/bin/bash
sudo apt install debian-archive-keyring debian-keyring

🔹6. Perform a Minimal Upgrade If Needed

A minimal upgrade helps resolve simpler updates without major dependency changes:

#!/bin/bash
sudo apt upgrade --without-new-pkgs -y

This avoids removing/installing packages prematurely and is recommended for minimal down time , great for if the system is provides critical services for your users or the network or full upgrade cannot be run due to space constraints.

🔹7. Full Distribution Upgrade to Debian 13 Trixie

Now complete the release upgrade to Debian 13:

#!/bin/bash
sudo apt full-upgrade -y

During this process:

If prompted about configuration files, generally keep the current version if you’ve heavily customized them.
Approve service restarts when prompted.

The full upgrade may install new library versions and remove obsolete packages as needed.

🔹8. Reboot and Verify

After the full upgrade:

#!/bin/bash
sudo reboot

Check the new release:

#!/bin/bash
cat /etc/os-release

You should see 13 (trixie) in the "VERSION".

Optional - After rebooting the system, verify that the upgrade completed successfully and that the system is running the expected Debian release. Note that neofetch is no longer actively maintained, so it is recommended to use fastfetch instead. And fastfetch was just added in Debian 13 repo, using sudo apt install fastfetch will work.

🔹9. Cleanup

After reboot:

#!/bin/bash
sudo apt autoremove -y
sudo apt autoclean

The release notes recommend removing obsolete or redundant packages since dependency graphs can change in the new release.

🔹10. Modernize APT Sources (Optional)

Debian 13 uses the deb822 sources format by default. To convert your old /etc/apt/sources.list into the new style:

#!/bin/bash
sudo apt modernize-sources

This will generate files like:

/etc/apt/sources.list.d/debian.sources
/etc/apt/sources.list.d/debian-backports.sources

The old style file is kept as a backup

🔹11. Clean Up Old `/tmp`

Debian 13 changes how /tmp is treated — it’s now typically mounted as a tmpfs, meaning its contents do not persist across reboots. Before upgrading, you might have stored temporary or large files there.

To inspect and remove old /tmp contents safely:

#!/bin/bash
sudo mkdir /mnt/tmp-folder
sudo mount --bind / /mnt/tmp-folder
ls -lha /mnt/tmp-chk/tmp/
# Remove temporary files if needed

Remove unwanted files interactively, then:

#!/bin/bash
sudo umount /mnt/tmp-folder
sudo rm -rf /mnt/tmp-folder

Cleaning large leftover files can free space and avoid confusion after the upgrade

🎯Conclusion & New Sources CLI Reference

Upgrading from Bookworm to Trixie is well-supported — but it still requires care:

Back up thoroughly.
Use tmux for safety on remote servers.
Read prompts and make informed decisions about configs.
Review and clean up outdated packages after upgrading.

APT Internet sources, path is the following in /etc/apt/sources.list.d/debian.sources:

#!/bin/bash
Types: deb
URIs: https://deb.debian.org/debian
Suites: trixie trixie-updates
Components: main non-free-firmware
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg

Types: deb
URIs: https://security.debian.org/debian-security
Suites: trixie-security
Components: main non-free-firmware
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg