# Upgrade Ubuntu or Debian to a new release

> Move a server to the next Ubuntu LTS with do-release-upgrade or from Debian 12 to Debian 13 as the release notes describe, with backups, checks and cleanup.

Difficulty: Advanced

Every release reaches the end of its free security updates, so a server that runs for years needs a release upgrade now and then. Ubuntu's `do-release-upgrade` and Debian's documented apt procedure upgrade the system in place: same server, same IP address, same data. This guide follows the official procedures.

## Before you start

- **Check the path.** Ubuntu upgrades from one LTS to the **next** LTS (22.04 → 24.04 → 26.04). Debian 13 supports upgrades only from Debian 12. See [Ubuntu's release cycle](https://ubuntu.com/about/release-cycle) for support dates.
- **Back up** your data and configuration, and test that you can restore it; see [backup strategy](/guides/backup-strategy-3-2-1). If your plan includes snapshots, take one as well.
- **Plan a maintenance window.** Services restart during the upgrade and the server reboots at the end.
- **Know your console.** If the network does not come up after the reboot, you need the server's console; see [server unreachable](/guides/server-unreachable).
- **Free space:** the upgrade downloads several hundred packages. Keep a few gigabytes free on `/` and enough on `/boot`.
- Read the release notes of the target release for software you run (databases, PHP, Python).

> **Tip**
>
> Run long upgrades inside `tmux` (`sudo apt install tmux`, then `tmux`). If your SSH connection drops, reconnect and run `tmux attach` to continue where you were.

## Upgrade Ubuntu to the next LTS

### Step 1: Bring the current release fully up to date

```bash
sudo apt update
sudo apt dist-upgrade -o APT::Get::Always-Include-Phased-Updates=true
```

Both must finish without errors. If the file `/run/reboot-required` exists, reboot and connect again:

```bash
ls /run/reboot-required && sudo reboot
```

### Step 2: Run the upgrade

```bash
sudo do-release-upgrade
```

The tool runs its checks, shows a summary and asks `Continue [yN]` before it changes anything. Third-party repositories (PPAs and vendor repositories) are disabled during the upgrade; note which ones you use so you can turn them back on later.

When a configuration file you changed differs from the new package's version, you are asked what to do: **N** or **O** keeps your file (the default), **Y** or **I** installs the new one, **D** shows the differences. Keep your file unless you know the new default is needed. Remove obsolete packages when asked, then reboot when prompted: the upgrade is not complete until the server has restarted.

### Step 3: Check the result

```bash
lsb_release -a
sudo apt update && sudo apt upgrade
```

## Upgrade Debian 12 to Debian 13

### Step 1: Prepare Debian 12

Bring Debian 12 up to date, then check for broken or held packages and for packages that do not come from Debian:

```bash
sudo apt update && sudo apt full-upgrade
cat /etc/debian_version
sudo dpkg --audit
apt-mark showhold
apt list '?narrow(?installed, ?not(?origin(Debian)))'
```

`dpkg --audit` must print nothing. Remove holds you no longer need and plan what to do with the non-Debian packages. Save the package selection for reference:

```bash
dpkg --get-selections '*' > ~/curr-pkgs.txt
```

### Step 2: Point APT at Debian 13

The release notes describe one file in the deb822 format. Create `/etc/apt/sources.list.d/debian.sources` with `sudo nano`:

```text
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
```

Then disable the old entries: remove `/etc/apt/sources.list` (or put `#` in front of every `bookworm` line) and any other Debian files under `/etc/apt/sources.list.d/`.

### Step 3: Upgrade in two stages

Refresh the lists and check the disk space the upgrade needs:

```bash
sudo apt update
sudo apt -o APT::Get::Trivial-Only=true full-upgrade
```

Then run the minimal upgrade first and the full upgrade second:

```bash
sudo apt upgrade --without-new-pkgs
sudo apt full-upgrade
```

Answer configuration questions as described for Ubuntu above. Make sure a kernel metapackage is installed before you reboot (`dpkg -l 'linux-image*' | grep ^ii`), then reboot.

### Step 4: Check and clean up

```bash
cat /etc/debian_version
sudo apt autoremove
sudo apt modernize-sources
```

`apt modernize-sources` converts any remaining old-format source files to the deb822 format.

## Check your services

**Verify:** the server boots into the new release, your services run (`systemctl --failed` lists nothing), your sites and applications respond, and `sudo apt update` shows no errors. Turn third-party repositories back on with their releases for the new system.

## Troubleshooting

**`No new release found`** (Ubuntu). The current release is not up to date yet (repeat Step 1 and reboot), or the next LTS has no point release yet. `sudo do-release-upgrade -c` only checks whether a new release is available.

**The upgrade stopped halfway.** Reconnect, attach to `tmux` if you used it, otherwise run `sudo dpkg --configure -a` and `sudo apt full-upgrade`; see [fix apt and dpkg errors](/guides/fix-apt-dpkg-errors).

**`Could not perform immediate configuration`** (Debian). The release notes give this workaround: `sudo apt full-upgrade -o APT::Immediate-Configure=0`.

**A service fails after the reboot.** Read its log with `sudo journalctl -u service-name -b` and compare its configuration file with the new package default, which apt saves next to yours with a suffix such as `.dpkg-dist` or `.ucf-dist`.

**The server is unreachable after the reboot.** Open the console and check `ip -brief address` and `systemctl status networking systemd-networkd`; see [server unreachable](/guides/server-unreachable).

## Next steps

- Keep the new release patched: [automatic updates](/guides/automatic-updates).
- Starting over is sometimes faster: [reinstall the operating system](/guides/reinstall-operating-system).

## Frequently asked questions

### Can I skip a release, for example from Ubuntu 22.04 to 26.04?

No. Ubuntu upgrades go from one LTS to the next one in sequence, and Debian supports upgrades only from the previous release. Upgrade in stages, or reinstall with the new release and move your data.

### Why does do-release-upgrade say there is no new release?

Upgrades to a new LTS are offered only after its first point release, for example 26.04.1. Before that, wait or reinstall with the new image. Development releases are not meant for servers.

### How long does a release upgrade take?

Usually between a quarter of an hour and an hour, depending on the number of packages and the questions you answer. Plan a maintenance window that includes the reboot and your checks.

### Is a fresh install better than an in-place upgrade?

For servers with years of changes, or when you skip several releases, a fresh install on a new server and a planned migration is often cleaner and easier to roll back. For a well-kept server, an in-place upgrade is quicker.

---

Source: <https://hyperdc.com/guides/products/upgrade-ubuntu-debian-release>\
Updated: 2026-10-15