Automatic system upgrades

Automatic system upgrades can be used to upgrade a system regularly at a specific time. This can help to reduce the time period of applying important security patches to your running software but might also introduce some breakage in case an automatic upgrade fails. For automatic upgrades an automatic garbage collection is important to prevent full /boot and / partitions.

Configuration

Channel-based systems (default)

Most NixOS installations use channels by default. If you're unsure which you're using, check with nix-channel --list. If that returns results, you're using channels.

For channel-based systems, use this configuration:

❄︎ auto-upgrade.nix

system.autoUpgrade = {
  enable = true;
  flags = [
    "--print-build-logs"
  ];
  dates = "02:00";
  randomizedDelaySec = "45min";
  allowReboot = false;  # Set to true if you want automatic reboots
};

Important: Do not use flake-specific flags with channel-based systems, as they will cause the upgrade to fail silently.

Flake-based systems

To enable unattended automatic system updates on a flake-enabled host, add following part to your configuration:

❄︎ auto-upgrade.nix

system.autoUpgrade = {
  enable = true;
  flake = "/path/to/flake";
  flags = [
    "--print-build-logs"
    "--commit-lock-file"  # If you want to automatically commit the updated flake.lock
  ];
  dates = "02:00";
  randomizedDelaySec = "45min";
};

Monitoring

Check that automatic system upgrades run successfully. Force an automatic system upgrade by running

# systemctl start nixos-upgrade

Check the upgrade log with

# systemctl status nixos-upgrade.service

Or, to see the full log

# journalctl -u nixos-upgrade.service

To see the status of the upgrade timer run

# systemctl status nixos-upgrade.timer

Troubleshooting

Git "repository is not owned by current user"

The flake repository directory is not owned by root (which nixos-upgrade runs as). To fix this, add the following to /root/.gitconfig:

≡︎ /root/.gitconfig

[safe]
  directory = /path/to/flake

Git "fatal: unable to auto-detect email address"

The root user doesn't have specified the user and email in the git configuration. To fix this, you can extend the nixos-upgrade service with:

❄︎ auto-upgrade.nix

systemd.services.nixos-upgrade.environment = {
  GIT_AUTHOR_NAME = "NixOS Auto-upgrade";
  GIT_AUTHOR_EMAIL = "root@<your-hostname>";
  GIT_COMMITTER_NAME = "NixOS Auto-upgrade";
  GIT_COMMITTER_EMAIL = "root@<your-hostname>";
};