Docker Build -t: Tagging and Securing Your Docker Images

Docker is a popular platform for developing, deploying, and running applications in containers. Docker containers allow developers to package and isolate applications with their dependencies, making it easier to deploy them across different environments. 

One of the most important commands in the Docker toolkit is the docker build -t command. In this blog post, we will explore this command and its usage in Docker.

What is docker build -t?

The docker build command is used to build Docker images from a Dockerfile. A Dockerfile is a text file that contains a set of instructions for building a Docker image. The docker build -t command is used to tag the resulting image with a name and an optional tag.

The -t option specifies the name and tag of the image. The format of the tag is <name>:<tag>. If the tag is not specified, it defaults to “latest.”

For example, the following command builds a Docker image from the Dockerfile in the current directory and tags it with the name myapp and the tag v1.0:

docker build -t myapp:v1.0 .

How does docker build -t work?

The docker build command reads the instructions in the Dockerfile and executes them in order to build the Docker image. Each instruction in the Dockerfile creates a new layer in the image. Docker caches the layers to speed up the build process. If a layer has not changed since the last build, Docker reuses the cached layer instead of rebuilding it.

The -t option is used to tag the final image with a name and tag. The name and tag are used to identify the image when it is pushed to a Docker registry or used to start a container.

Best practices for using docker build -t

When using the docker build -t command, it is important to follow best practices to ensure that the resulting image is secure and efficient.

1. Use a specific tag

When tagging the Docker image, it is important to use a specific tag instead of the default latest tag. Using a specific tag makes it easier to manage and deploy multiple versions of the image.

2. Use a .dockerignore file

The .dockerignore file is used to specify files and directories that should be excluded from the build context. This reduces the size of the build context and speeds up the build process.

3. Keep layers small

Each instruction in the Dockerfile creates a new layer in the image. It is important to keep each layer small to reduce the size of the final image. This makes the image easier to distribute and reduces the risk of security vulnerabilities.

4. Use multi-stage builds

Multi-stage builds are a powerful feature of Docker that allows you to use multiple Dockerfiles to create a single image. This is useful for building images that require multiple dependencies or tools. Using multi-stage builds can reduce the size of the final image and make it easier to maintain.

The docker build -t command is a powerful tool for building Docker images from Dockerfiles. By following best practices, you can create secure and efficient Docker images that are easy to manage and deploy. When building Docker images, it is important to keep in mind the size of the image, the security of the image, and the ease of deployment. With these considerations in mind, you can use Docker to build powerful and scalable applications that can run anywhere.

Low-code Tasks and Pipelines With Ozone

The best thing to do next is to automate the build process itself as part of a pipeline where the workflow would proceed to test and scan the Docker image for vulnerabilities. While there’s considerable scripting going on already, you wouldn’t want to spend time scripting your pipelines as well. You can give Ozone a shot as it uses a GUI to drag and drop tasks from a catalog of templates (with even the docker build as one of the many tasks) to build the pipeline, thus saving crucial time for DevOps teams.