Automating Docker Image Tag Incrementation for Local Development and Repository Pushes

Introduction

In the world of continuous integration and continuous deployment (CI/CD), maintaining a streamlined process for building and deploying Docker images is crucial. A common challenge is how to automatically increment image tags in a local development environment before pushing them to a Docker registry. In this post, we’ll explore a simple yet effective script to automate this process, ensuring a smooth and error-free workflow.

The Need for Automation

Managing Docker image versions manually can be error-prone and time-consuming. Automatic tag incrementation ensures that each new build has a unique identifier, making it easier to track and deploy specific versions of your application.

Setting Up the Script

We’ll create a bash script that does the following:

• Increments the image tag based on a version file.
• Builds the Docker image with the new tag.
• Pushes the image to a specified Docker registry.

Prerequisites

• Docker installed on your system.
• A Docker registry where images will be pushed (e.g., Docker Hub, Google Container Registry).
• Basic knowledge of bash scripting.

Script Breakdown

Step 1: Define Input Parameters

The script accepts four parameters:

• Registry URL (default: asia-docker.pkg.dev).
• Image name (default: user-service).
• Tag base (default: 0.0).
• Location of the version file (default: version.txt).

REGISTRY_URL=${1:-"asia-docker.pkg.dev"}
IMAGE_NAME=${2:-"user-service"}TAG_BASE=${3:-"0.0"}
VERSION_FILE=${4:-"version.txt"}

Step 2: Check and Create Version File

The script checks if the version file exists; if not, it creates one and initialises it with 0.

if [ ! -f "$VERSION_FILE" ]; then
    echo "0" > "$VERSION_FILE"
fi

Step 3: Read and Increment Version

It reads the current version, increments it, and uses it as part of the tag.

VERSION=$(cat "$VERSION_FILE")
NEW_VERSION=$((VERSION+1))

Step 4: Build and Tag the Docker Image

The image is built with the new tag and then tagged for the specified registry.

docker build -t ${IMAGE_NAME}:${TAG_BASE}.$NEW_VERSION .

docker tag ${IMAGE_NAME}:${TAG_BASE}.$NEW_VERSION $REGISTRY_URL/docker-registry/${IMAGE_NAME}:${TAG_BASE}.$NEW_VERSION

Step 5: Push to Registry

The newly tagged image is pushed to the Docker registry.

docker push $REGISTRY_URL/docker-registry/${IMAGE_NAME}:${TAG_BASE}.$NEW_VERSION

Step 6: Update Version File and Output

The version file is updated with the new version number, and a confirmation message is displayed.

echo $NEW_VERSION > "$VERSION_FILE"
echo "Docker build, tag, and push for ${IMAGE_NAME} version ${TAG_BASE}.$NEW_VERSION complete."

Running the Script

To use the script, simply run it from your command line, optionally passing the desired parameters. For example:

./build_and_push_docker.sh custom-registry.com my-image 1.0 /path/to/my/version.txt

Reference:

https://gist.github.com/ucguy4u/e15be48d235daf9642353b20f2b7ab70

Conclusion

Automating the Docker image tag incrementation and pushing process simplifies the development workflow, reduces human error, and ensures a consistent versioning system. By integrating this script into your development pipeline, you can focus more on development and less on the intricacies of Docker image management.