Watchtower — Automated Docker Updates on a Synology NAS

Please note if you are using DSM7.2 or higher you should use the Container Manager version of this guide from the menu.

This guide has reached the end of its updates as most people are now on the latest DSM update - This guide is correct as of 08/12/2023 however no further updates will be added.

What is Watchtower?

Watchtower is an application that watches for updates for all your containers and automatically updates them for you.

Let’s Begin

Watchtower requires access to the Docker socket, we are unable to set this up via the Synology GUI. This means we will be using Docker-Compose.

Docker Compose

We will be using Docker Compose to set up the container. In a nutshell we will be creating a text file (YAML formatted) which tells Docker exactly how we want to set up a specific container.

The next steps can be done either using a code/text editor such as Notepad++ or to keep things simple for this guide we will be using the Synology Text Editor which can be installed from the Package Center.

Open up Text Editor and click on File then New to start a new file.

We have a couple of different composes available below the first one is configured to update all running containers at 2am daily (UTC).

services:
  watchtower:
    image: containrrr/watchtower:latest
    container_name: watchtower
    environment:
      - TZ=YOURTIMEZONE
      - WATCHTOWER_CLEANUP=true
      - WATCHTOWER_INCLUDE_STOPPED=true
      - WATCHTOWER_REVIVE_STOPPED=false
      - WATCHTOWER_SCHEDULE=0 0 2 * * *
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    restart: unless-stopped

As an addition to the method above you can exclude specific containers from updates by adding this line to their yaml (compose) details. This is likely faster than using method 2

    labels:
      - com.centurylinklabs.watchtower.enable=false

The second has an added section where you can specify the names of the containers you would like to update (use the exact name of the container as per the Synology UI)

You can copy and paste the one you wish to use into the new text file, it is important you don’t change the spacing as YAML has to be formatted correctly in order to be read by Docker Compose.

services:
  watchtower:
    image: containrrr/watchtower:latest
    container_name: watchtower
    environment:
      - TZ=YOURTIMEZONE
      - WATCHTOWER_CLEANUP=true
      - WATCHTOWER_INCLUDE_STOPPED=true
      - WATCHTOWER_REVIVE_STOPPED=false
      - WATCHTOWER_SCHEDULE=0 0 2 * * *
    command: # add or remove the below as required
      - nzbget
      - overseerr
      - plex
      - prowlarr
      - radarr
      - sonarr
      - tautulli
      - watchtower
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    restart: unless-stopped

Environment Variables

We need to make some changes in order for watchtower to know what time it is where you are and what we want it to do. You can amend these based on your preferences.

Your final file should look similar to the one shown below, depending on which version you used above.

Saving the Compose File

We now need to save this file into our docker share

Click on File then Save As, navigate to the ‘docker’ share and you need to change the ‘File name’ to watchtower.yml and save it in the ‘docker’ folder.

SSH and Docker-Compose

It’s time to get logged into you Diskstation via SSH, you can do this in the same way as when you obtained your IDs in the ‘Setting up a restricted Docker user‘ guide.

Once you have logged in you will need to give 2 commands, you can copy and paste these one at a time — you will need to enter your password for the command starting with ‘sudo’

First we are going to change directory to where the watchtower.yml is located, type the below and then press enter.

cd /volume1/docker

Then we are going to instruct Docker Compose to read the file we created and complete the set-up the container. Again type the below and press enter.

sudo docker-compose -f watchtower.yml up -d

When the command has completed you should be able to see Watchtower running in the list of containers in the Synology GUI. You can go into the container and within the log you should see that Watchtower is counting down to your next check.

You can now just leave Watchtower running you will never need to manually update your containers again.

FAQ

Q: I keep getting X container has stopped unexpectedly errors!
A: DSM does not know or understand that Watchtower is issuing commands in the background. So it makes the assumption that it was stopped unexpectedly, but we know it was Watchtower doing an update, the same happens if you issue a commands via docker-compose or even Portainer.

Q: Do I need to update Watchtower itself?
A: Nope it updates itself – quite clever really 🙂

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