Step 2: Modifying a Docker Image

Objective: Modify a docker to include updated packages.

One problem with projects on GitHub is that they get stale. A developer built the project for their current need but then didn’t maintain it.

Tip

We should modify Docker projects with up-to-date packages.

4.2.1 Updating old Code

The version of Node in the pandoc-as-a-service Dockerfile has a long list of published security vulnerabilities. We will replace Node 6.10 with the latest version of Node (v 15.2) in DockerHub.

  1. Edit the pandoc-as-a-service Dockerfile and replace the version of Node.

    FROM node:latest
    
    # Create app directory
    COPY . /usr/src/pandoc-as-a-service
    WORKDIR /usr/src/pandoc-as-a-service
    . . .
    
  2. Let’s try to rebuild. It will fail because we need to make additional changes, but we’ll do them one at a time.

    We will give our updated version a new tag (latest).

    docker build -t pandoc:latest .
    
  3. npm audit found a problem!

    1
    2
    3
    4
    7 vulnerabilities (3 low, 2 high, 2 critical)
    
    To address all issues (including breaking changes), run:
      npm audit fix --force
    
  4. The fix is simple. We need to append npm audit fix --force to the RUN command.

    # Install packages
    RUN apt-get update --fix-missing \
      && apt-get install -y pandoc \
      && apt-get clean \
      && rm -rf /var/lib/apt/lists/* \
      && npm install \
      && npm audit fix --force
    
  5. Save the file and then rerun the same build command to fix the issues.

     7 vulnerabilities (3 low, 2 high, 2 critical)
    
     To address all issues (including breaking changes), run:
       npm audit fix --force
    
     Run `npm audit` for details.
     npm notice
     npm notice New patch version of npm available! 7.0.8 -> 7.0.10
     npm notice Changelog: <https://github.com/npm/cli/releases/tag/v7.0.10>
     npm notice Run `npm install -g npm@7.0.10` to update!
     npm notice
     npm WARN using --force Recommended protections disabled.
     npm WARN audit Updating mocha to 8.2.1,which is a SemVer major change.
    
     added 90 packages, removed 9 packages, changed 9 packages, and audited 194 packages in 4s
    
     15 packages are looking for funding
       run `npm fund` for details
    
     found 0 vulnerabilities
     Removing intermediate container 6c3ea353ed6f
    
  6. We can also update the HTML by modifying views/index.ejs. For example, we updated the URLs in the code on our pandoc.bilimedtech.com site.

4.2.2. Cleanup Failed Builds

Docker will tag an image as <none> anytime the build fails.

Failed Builds
root@vps298933:~/pandoc-as-a-service# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
pandoc              latest              79ad25bc9c62        11 seconds ago      1.03GB
<none>              <none>              5847e41654f3        14 minutes ago      1.03GB
<none>              <none>              deec2993cbc8        22 minutes ago      1.02GB
pandoc              default             7eb0798f4080        6 hours ago         720MB
node                latest              f1974cfde44f        36 hours ago        935MB
mariadb             latest              2ab9d091310d        39 hours ago        414MB
nextcloud           latest              3ed6ea445002        7 days ago          811MB
wordpress           latest              6edecd0f5c75        7 days ago          546MB
redis               latest              62f1d3402b78        2 weeks ago         104MB
node                6.10                3f3928767182        3 years ago         661MB

Tip

Remove the unused images using the command: docker rmi IMAGE_ID

For example, we can remove the two images above using:

docker rmi 5847e41654f3
docker rmi deec2993cbc8
Output
root@vps298933:~/pandoc-as-a-service# docker rmi 5847e41654f3
Deleted: sha256:5847e41654f3cf0a46c27e945e405b3489d1d18a9c879b8a5efbfac5d9ec9067
Deleted: sha256:d0fb7d96057e7a465b59ed72d085f0eead2b8a4dda69700098a1ad26c78b50da
Deleted: sha256:f9c88be69a1f5c321eac2630990f13bfc3a86aa06f7a8e4d16c276e73ba397f7
Deleted: sha256:1d64eef5852b108a449afbac6c6c052f1d18737ee4d682beb3cd2e3dcb0347d5
Deleted: sha256:ef049b742654a3f283b81b6316c3bff4e64c9ab8393fed77cda150f31679b1ae
Deleted: sha256:3ad253af23d8e51634b39eea4f7616e7b035ba3e3f04c1dbc5e1bd0b8897adf3
Deleted: sha256:bdc818d89e59373738c425951cb5d392a34284530539b9584ab358a9df239748
root@vps298933:~/pandoc-as-a-service#
root@vps298933:~/pandoc-as-a-service# docker rmi deec2993cbc8
Deleted: sha256:deec2993cbc88b7002e3bd9ece516b0694e93961cb0cfe7668a1bd1f8738ece0
Deleted: sha256:922ce00047ef1ab341768c4ad1a2a1991d4c7b0d4825b0014126a363a53d88a2
Deleted: sha256:674e57717b3b0ff7d0bc05ec8ffa81d7354266139e7272ff12343ce211ba84eb
Deleted: sha256:3afad23927db55d4cf44f576df7682f19c85d93959d4c939cd2bf81003a08f8b
Deleted: sha256:9ff091f132f82f82843fa1f75954077ad9276f10845df88843ed464a29a0fe11
Deleted: sha256:4c464b8d162e93c6391a11b7d48e0531c3a489571817522202715d871a486a49
Deleted: sha256:b6831928fccd0c0c6b961024846544dec21fcf540dea22a41006903fae01f0c4
Deleted: sha256:dc62fb20fb9ead1ab565487b3c44ec6fb970a124272070c8726643d292373b6c
Deleted: sha256:5bbec8dd291ea1213ac73bd5079000a2c89deaa10aedd070ea12fb090160b589
Deleted: sha256:4242bfc2cb701c295cf7fdcc72011e5fde65530610f0d5cd2b3549cffb1da2f8
root@vps298933:~/pandoc-as-a-service#
root@vps298933:~/pandoc-as-a-service# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
pandoc              latest              79ad25bc9c62        6 minutes ago       1.03GB
pandoc              default             7eb0798f4080        6 hours ago         720MB
node                latest              f1974cfde44f        36 hours ago        935MB
mariadb             latest              2ab9d091310d        40 hours ago        414MB
nextcloud           latest              3ed6ea445002        7 days ago          811MB
wordpress           latest              6edecd0f5c75        7 days ago          546MB
redis               latest              62f1d3402b78        2 weeks ago         104MB
node                6.10                3f3928767182        3 years ago         661MB
root@vps298933:~/pandoc-as-a-service#

4.2.3 Relaunch with the updated Images

The final step is to update the docker-compose.yml file with the new tag. Also, let’s add a volume for the source code so that we can change it without rebuilding the image.

  1. Change to the project directory, update the image name, and then restart

    cd ~/pandoc-docker
    nano docker-compose.yml
    docker-compose down && docker-compose up -d
    
    docker-compose.yml
     version: "3.3"
    
     services:
       pandoc:
         image: pandoc:latest
         ports:
           - 20852:8080
         restart: always
    
  2. Verify that the new image is in use.

     root@vps298933:~/pandoc-docker# docker ps
     CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                     NAMES
     9aaf93a4aa5b        pandoc:latest       "docker-entrypoint.s…"   38 seconds ago      Up 35 seconds       0.0.0.0:20852->8080/tcp   pandocdocker_pandoc_1
     1a13f235f757        nextcloud           "/entrypoint.sh apac…"   10 hours ago        Up 10 hours         0.0.0.0:20850->80/tcp     nextclouddocker_app_1
     74b008e6fc1a        redis:latest        "docker-entrypoint.s…"   10 hours ago        Up 10 hours         6379/tcp                  nextclouddocker_redis_1
     de86f8cd7ca1        mariadb:latest      "docker-entrypoint.s…"   10 hours ago        Up 10 hours         3306/tcp                  nextclouddocker_db_1
     cd832a14a92c        wordpress:latest    "docker-entrypoint.s…"   23 hours ago        Up 23 hours         0.0.0.0:20851->80/tcp     wordpressdocker_wordpress_1
     b61ce1aedf86        redis               "docker-entrypoint.s…"   23 hours ago        Up 23 hours         6379/tcp                  wordpressdocker_redis_1
     651734395eb0        mariadb:latest      "docker-entrypoint.s…"   23 hours ago        Up 23 hours         3306/tcp                  wordpressdocker_db_1
     root@vps298933:~/pandoc-docker#
    
  3. Open the URL in the browser that it works.