Using Watchtower to Keep Containers Up to Date

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Using Watchtower to Keep Containers Up to Date

Tired of having to manually update several containers, you’ve decided to look for an automated solution. After doing some research, you have discovered Watchtower. Watchtower is a container that updates all running containers when changes are made to the image that it is running. You will need to create a Dockerfile that will be used to create a Docker image. The image will be pushed to Docker Hub. Next, you will create a container using this image. Once the image is created, you will deploy the Watchtower container. After Watchtower is deployed, you will update the Dockerfile, rebuild the image, and push the changes to Docker Hub. Watchtower checks for changes every 30 seconds. Once it detects the changes, Watchtower will update the running container. For more information on Watchtower you can go [here](https://github.com/v2tec/watchtower).

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Lab Info

Level

Intermediate

Last updated

Apr 06, 2025

Duration

1h 0m

Challenge

Create the Dockerfile

Create a Dockerfile:

[cloud_user@host]$ vi Dockerfile

The Dockerfile should contain the following:

FROM node
RUN mkdir -p /var/node
ADD src/ /var/node/
WORKDIR /var/node
RUN npm install
EXPOSE 3000
CMD ./bin/www

Challenge

Build the Docker Image

Build the Docker image:

[cloud_user@host]$ docker image build -t USERNAME/lab-watchtower -f Dockerfile .

Challenge

Push the Image to Docker Hub
Login to Docker Hub:
```
docker login
```
Push the image to Docker Hub:
```
docker image push USERNAME/lab-watchtower
```

Challenge

Create a Demo Container

Create the container that Watchtower will monitor:

[cloud_user@host]$ docker container run -d --name demo-app -p 80:3000 --restart always USERNAME/lab-watchtower

Challenge

Create the Watchtower Container

Create the Watchtower container that will monitor the demo-app container:

[cloud_user@host]$ docker run -d --name watchtower --restart always -v /var/run/docker.sock:/var/run/docker.sock v2tec/watchtower -i 30

Challenge

Update the Docker Image

After creating /var/node, add an instruction to create /var/test.

Update the Docker image:

[cloud_user@host]$ vi Dockerfile

Add change to Dockerfile:

RUN mkdir -p /var/test

Rebuild the image:

[cloud_user@host]$ docker build -t USERNAME/lab-watchtower -f Dockerfile .

Push the new image:

[cloud_user@host]$ docker image push USERNAME/lab-watchtower

About the author

Pluralsight Skills

Pluralsight Skills gives leaders confidence they have the skills needed to execute technology strategy. Technology teams can benchmark expertise across roles, speed up release cycles and build reliable, secure products. By leveraging our expert content, skill assessments and one-of-a-kind analytics, keep up with the pace of change, put the right people on the right projects and boost productivity. It's the most effective path to developing tech skills at scale.

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