Upgrading your VPS to a new version of Debian or Ubuntu

Every version of Debian and Ubuntu gets security updates for a fixed period. After that it is end of life: your server keeps running, but vulnerabilities are no longer patched. Automatic updates won't take you to the next version. You do that yourself, with a release upgrade. Here's how to do it safely, from Debian 12 to 13 and from Ubuntu 24.04 to 26.04.

Do I need to upgrade yet?

You can see which version you have with cat /etc/os-release. As of November 2026:

Check the current dates at debian.org/releases and ubuntu.com/about/release-cycle, and put your server's end date in your calendar. Install a new server with Debian 13 or an Ubuntu LTS version. Never skip a version: going from Debian 11 to 13 goes through 12.

Upgrade or rebuild?

You can update the existing server (an in-place upgrade) or do a clean install with the new version and restore your data. For a small server with a few services, an in-place upgrade is fine. If it runs a lot of custom setup, or the server has already been upgraded several times, reinstalling is often just as quick, see Mounting your own ISO or reinstalling your VPS.

Preparation

1. Take a snapshot right before you start, and make sure you have a recent backup stored off the server. See Snapshots and backups of your VPS and Backups with restic to another location.
2. Test the console in the VPS screen and make sure you know the root password. If SSH breaks during the upgrade, you can still get in there. See The console: your VPS in your browser.
3. Read the release notes, especially the section on issues to be aware of. For Debian 13, for example, they mention that /etc/sysctl.conf is no longer read (use /etc/sysctl.d/).
4. Review third-party package sources with ls /etc/apt/sources.list.d/. Software that doesn't come from Debian or Ubuntu itself is the biggest source of problems. Check whether the vendor already has a version for the new release.
5. Work in tmux (sudo apt install tmux, then tmux). If your connection drops, the upgrade keeps running and you can pick it up again with tmux attach.
6. Fully update the current version first: sudo apt update && sudo apt full-upgrade, and reboot if needed.

Debian 12 to 13

Following the Debian 13 release notes, as root:

sed -i 's/bookworm/trixie/g' /etc/apt/sources.list.d/debian.sources
apt update
apt upgrade --without-new-pkgs
apt full-upgrade
reboot

If your sources are still in /etc/apt/sources.list, change the codename there instead. Temporarily disable third-party sources during the upgrade and re-enable them afterwards with the new codename, if the vendor provides one. If the upgrade asks whether you want to keep a configuration file you've modified (such as sshd_config), keep your own version if you know why you changed it, and compare it with the new version afterwards (the file ending in .dpkg-dist).

Ubuntu 24.04 to 26.04

sudo do-release-upgrade

Ubuntu only offers the upgrade from one LTS version to the next after the first point release, so from 26.04.1 onwards. That's deliberate: the biggest problems get fixed in the first few months. If you get a message saying there's no new version, just wait. If you run the upgrade over SSH, the program starts an extra SSH server on a backup port as a precaution. You usually won't need it, since you have the console.

After the upgrade

• Check the version with cat /etc/os-release.
• systemctl --failed should be empty, see Managing services with systemctl on your VPS.
• Clean up old packages with sudo apt autoremove.
• Check that your websites, containers and monitoring still work.
• If everything works, delete the snapshot: it grows with every change.

On AlmaLinux and Rocky Linux, a major version (9, 10) gets about ten years of updates, and you update between minor versions with sudo dnf upgrade. For a jump to a new major version, many administrators choose to reinstall.

Want to learn more? Take the free course VPS and Linux server management, lesson 4.3 Lifecycle and release upgrades.