Caution Upgrading from Debian 12 to Debian 13 on machines with mdadm has intermittently failed for me; symptom is that grub EFI is not up to date and system boots into BIOS. Root cause under investigation; it might not be related to mdadm.
To start, read the official release notes.
If your install fits into "vanilla Debian plus maybe a handful of 3rd-party repos", then this guide for a simple upgrade to Debian 13 "trixie" from Debian 12 "bookworm" can be helpful. 3rd-party repos are handled with a find command.
Note upgrade is only supported from Debian 12 to Debian 13. If you are on Debian 11, upgrade to Debian 12 first. Then once on Debian 12, you can upgrade to Debian 13.
This guide is only for the OS itself. Applications are as plentiful as sand on the beach, and they may all require additional steps. Plan for that.
- Check free disk space
df -h
5 GiB free is a conservative amount. sudo apt clean and sudo apt autoremove can be used to free some disk space.
On a server with only docker installed, even 1 GiB free was sufficient. Do err on the side of caution here, however.
- Identify any 3rd-party repos that may need to be updated. They'll be changed with a
findcommand, below.
ls /etc/apt/sources.list.d
- Update current distribution
sudo apt update && sudo apt full-upgrade
If this brought in a new kernel, sudo reboot - otherwise continue
- Change repo to trixie, from bookworm.
sudo sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
non-freehas been split since Debian 12 and if used, you should also usenon-free-firmware. If you are unsure, check and adjust. More complete instructions are in the Debian release notes and the gist for Debian 12 upgrade
- Change all 3rd-party repos
This assumes the repos have trixie versions. Run
sudo apt updateafter the change to trixie to confirm, and deal with any repos that aren't available in trixie.
sudo find /etc/apt/sources.list.d -type f -exec sed -i 's/bookworm/trixie/g' {} \;
- Optional: Start a screen session
So that an SSH disconnect doesn't stop your upgrade halfway through, you can run in screen: sudo apt install -y screen && screen
- Hold
mdadmif it's in use
If you use the mdadm package, as of Aug 22nd 2025, you'll want a workaround to avoid an issue where mdadm is updated
before systemd and shows an error that it cannot find systemd. A bug report tracks this.
Hold mdadm, update Debian, then unhold mdadm and update again.
sudo apt-mark hold mdadm
- Update Debian
For the following, say Yes to restarting services, and keep existing config files when prompted.
sudo apt update && sudo apt full-upgrade
- Update
mdadmif it's in use
This is a workaround for an order-of-operations issue, see above.
sudo apt-mark unhold mdadm
sudo apt update && sudo apt full-upgrade
mdadm should be updated without an error message about not finding systemd
- Reboot
sudo reboot
- Clean up old repos
sudo apt autoremove && sudo apt clean
- Modernize Debian sources
Optional but recommended: Switch to deb822 format for the sources.list. This will write /etc/apt/sources.list.d/debian.sources and /etc/apt/sources.list.d/debian-backports.sources
sudo apt modernize-sources
Caveat that trixie-backports might not have a
Signed-Byon some 3rd-party mirrors. You can fix this by manually settingSigned-By: /usr/share/keyrings/debian-archive-keyring.gpgin/etc/apt/sources.list.d/debian-backports.sources
Config ansible.cfg:
[defaults]
interpreter_python = /usr/bin/python3
Playbook trixie.yml:
---
- name: Upgrade to Debian trixie
hosts: all
serial: 1
gather_facts: false
roles:
- base/upgrade_trixie
Role base/upgrade_trixie/tasks/main.yml:
---
- name: Get distribution version
setup:
filter: ansible_distribution*
- name: Skip if not Debian 12
meta: end_host
when: ansible_distribution != 'Debian' or ansible_distribution_major_version != '12'
- name: apt clean
apt:
clean: yes
become: yes
- name: Get filesystem facts
setup:
filter: ansible_mounts
- name: Fail if free space on / is below 5 GiB
ansible.builtin.assert:
that:
- item.size_available > (5 * 1024 * 1024 * 1024)
fail_msg: "Free disk space on {{ item.mount }} is below 5 GiB"
loop: "{{ ansible_mounts }}"
when: item.mount == "/"
- name: All apt packages up to date
apt:
upgrade: dist
update_cache: yes
become: yes
- name: apt autoremove
apt:
autoremove: yes
become: yes
- name: apt clean
apt:
clean: yes
become: yes
- name: Check if reboot required
ansible.builtin.stat:
path: /run/reboot-required
get_checksum: no
register: reboot_required_file
- name: Reboot if required
ansible.builtin.reboot:
msg: "Reboot initiated by Ansible"
connect_timeout: 5
reboot_timeout: 600
pre_reboot_delay: 0
post_reboot_delay: 60
test_command: whoami
when: reboot_required_file.stat.exists
become: true
- name: Switch OS from bookworm to trixie
ansible.builtin.replace:
path: /etc/apt/sources.list
regexp: 'bookworm'
replace: 'trixie'
become: yes
- name: Find all 3rd-party repos
ansible.builtin.find:
paths: /etc/apt/sources.list.d
patterns: '*'
recurse: no
register: third_party_repos
- name: Switch 3rd-party repos from bookworm to trixie
ansible.builtin.replace:
path: "{{ item.path }}"
regexp: 'bookworm'
replace: 'trixie'
loop: "{{ third_party_repos.files }}"
loop_control:
label: "{{ item.path }}"
become: yes
- name: Use apt to move to trixie
apt:
upgrade: dist
update_cache: yes
become: yes
- name: Get distribution version
setup:
filter: ansible_distribution*
- name: Fail if not Debian 13
assert:
that:
- ansible_distribution_major_version == '13'
fail_msg: "Upgrade to Debian 13 failed"
- name: apt autoremove
apt:
autoremove: yes
become: yes
- name: apt clean
apt:
clean: yes
become: yes
- name: Reboot on trixie
ansible.builtin.reboot:
msg: "Reboot initiated by Ansible"
connect_timeout: 5
reboot_timeout: 600
pre_reboot_delay: 0
post_reboot_delay: 60
test_command: whoami
become: yes
- name: Modernize apt sources
ansible.builtin.command:
cmd: apt -y modernize-sources
become: yes
- name: Pause for 5 minutes for staggered upgrades
pause:
minutes: 5
Some 3rd party repositiories were throwing "Skipping acquire of configured file...blah blah....stable InRelease doesn't support architecture 'i386'
If you have run the modernize-sources, there is a new format for setting an architecture....the old way arch=amd64 won't work.
You must put the line such as the following in the affected sources files:
Architectures: amd64