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Upgrading a server's operating system ​

When Moatline reports an operating system out of support — Ubuntu 20.04 since 2025-05-31, Debian 11 since 2026-08-31 — the server gets no security updates any more, however well unattended-upgrades runs. There are three ways off it.

1. A new server, apps moved over (safest) ​

Best for servers that carry customer sites: the old server keeps running until the new one is proven.

  1. Create a server with Ubuntu 24.04 LTS (or Debian 13), harden it and install the agent from the Setup tab.
  2. Dokploy: add it under Remote servers, move each application and database to it (or create them there) and deploy. Restore databases from their backups. Coolify: add the server and move the resources the same way.
  3. Check every site on the new server — Moatline's live checks and checks tell you when all are green.
  4. Move the IP (below) or switch DNS, then shut the old server down.

2. Upgrade in place ​

Possible, one release at a time — there is no direct jump from 20.04 to 24.04. Plan a maintenance window, roughly 20–40 minutes per release with short outages.

bash
# 0. Take a snapshot in your provider's console — your way back.

# 1. Bring the current release fully up to date
sudo apt update && sudo apt full-upgrade -y
sudo reboot

# 2. At least ~5 GB free on /
df -h /

# 3. Run the upgrade inside tmux, so a dropped SSH session does not kill it
sudo apt install -y tmux && tmux
sudo do-release-upgrade     # 20.04 → 22.04, reboot when asked
sudo do-release-upgrade     # 22.04 → 24.04 after the reboot
  • Third-party repositories are switched off during the upgrade — Docker, CrowdSec, Tailscale. Re-enable them in /etc/apt/sources.list.d/ with the new codename (focal → jammy → noble), then sudo apt update && sudo apt full-upgrade.
  • The upgrader opens SSH on port 1022 as a fallback and asks first when a firewall is active.
  • Docker containers come back after the reboot; check the sites are green.

For Debian, change the codename in the APT sources (bullseye → bookworm → trixie), apt full-upgrade, reboot — one release at a time.

3. Buy time with extended support ​

Ubuntu Pro keeps 20.04 patched until 2030: sudo pro attach <token>. Free for personal use on up to five machines; for a business it is paid. A bridge, not a replacement — plan the upgrade anyway.

Keeping the server's IP ​

DNS, firewall allowlists at customers and partners often point at the IP. Whether it can stay depends on the provider:

ProviderHow the IP stays
Hetzner CloudThe primary IP is its own resource. Power off the old server, Networking → Primary IPs → Unassign, power off the new one, unassign its own primary IP, assign the old one. Turn off auto delete on the IP before deleting the old server, or it goes with it.
Hetzner Cloud, in placeRebuild reinstalls the image on the same server and keeps the IP — but wipes the disk: back up everything first.
Hetzner dedicated (Robot)Reinstalling with installimage keeps the IP; a new server gets a new one, unless you use a failover IP.
Other cloudsMost have the same idea: elastic, reserved or static IPs (AWS, DigitalOcean, Vultr) that move between servers.

For next time, point DNS at a floating IP (Hetzner) instead of the server's own: it moves to another server in seconds, without powering anything off.

After the move:

  • SSH warns that the host key changed — expected; remove the old line with ssh-keygen -R <ip>.
  • In Dokploy, the remote server needs its SSH key again (Remote servers → Setup).
  • Install the agent on the new server; keep the server's address in Moatline as it is.