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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](

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Path Info

Clock icon Intermediate
Clock icon 1h 0m
Clock icon Apr 04, 2019

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Table of Contents

  1. 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
  2. Challenge

    Build the Docker Image

    Build the Docker image:

    [cloud_user@host]$ docker image build -t USERNAME/lab-watchtower -f Dockerfile .
  3. 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
  4. 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
  5. 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
  6. 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

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