How to Create Docker Images using Dockerfile?

The following article describes How to Create Docker Images using Dockerfile.

Basically, a Dockerfile contains a set of instructions for building a Docker image. In fact, it is a simple text file. Further, these instructions are executed in sequence to create the image. So, the Dockerfile specifies the base image to use, the commands to run, the files to copy, and the ports to expose.

In order to create a Docker image, you need to write a Dockerfile that includes the following instructions.

1. FROM. The FROM instruction allows us to choose the base image. So, we can use it for the Docker image. Hence, the base image is the starting point for building the image.
2. WORKDIR. To set the working directory. Hence, it will be used for any subsequent instructions that are executed in the Dockerfile.
3. COPY. Basically, it is for copying files and directories. The COPY instruction copies from the host machine to the Docker image.
4. RUN. Actually, it executes a command in the Docker image.
5. EXPOSE. To specify the port where the container will listen.
6. CMD. The CMD instruction specifies the command to run when the Docker container starts.

Once you have written the Dockerfile, you can use the “docker build” command to create the Docker image. In fact, the “docker build” command reads the Dockerfile and builds the image based on the instructions in the file. The following code shows the basic syntax for building an image.

docker build [OPTIONS] PATH

Here, [OPTIONS] are additional options that you can pass to the build command, and PATH is the path to the directory where the Dockerfile is available.

For example, we can use the following command to build the image.

docker build -t myimage:1.0 .

As can be seen, this command builds the Docker image and tags it with the name “myimage” and the version “1.0”. Also, the “.” at the end of the command specifies that the Dockerfile is located in the current directory.

Once the Docker image is built, you can use the “docker run” command that starts a container. As a result, we get a new container.

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