How to Set Image Name in Dockerfile

TLDR

To set an image name in Docker, you use the docker build command with the -t flag. The image name is not directly set in the Dockerfile but is specified during the build process.

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Docker images are a fundamental part of containerized workflows. While the Dockerfile defines the instructions for building an image, the image name is set during the build process using the docker build command. This guide will show you how to set and manage image names effectively.

Step 1: Create a Dockerfile

Start by creating a Dockerfile with the necessary instructions to build your image.

Example Dockerfile

FROM node:18
WORKDIR /app
COPY . .
RUN npm install
CMD ["node", "app.js"]

Explanation

• FROM node:18: Specifies the base image.
• WORKDIR /app: Sets the working directory inside the container.
• COPY . .: Copies files from the current directory into the container.
• RUN npm install: Installs dependencies.
• CMD ["node", "app.js"]: Starts the application.

Step 2: Build the Image with a Name

Use the docker build command with the -t flag to set the image name.

Command

docker build -t my-app:latest .

Explanation

• -t my-app:latest: Sets the image name to my-app and the tag to latest.
• .: Specifies the build context (current directory).

Step 3: Verify the Image Name

After building the image, verify its name using the docker images command.

Command

To list all Docker images and confirm the name:

docker images

Example Output

REPOSITORY   TAG       IMAGE ID       CREATED         SIZE
my-app       latest    abc123def456   5 minutes ago   123MB

Best Practices

• Use Descriptive Names: Choose names that reflect the purpose of the image.
• Tag Versions: Use tags like v1.0 or latest to manage versions.
• Automate Naming: Use CI/CD pipelines to automate image naming and tagging.

By following these steps, you can effectively set and manage image names in Dockerfiles, ensuring streamlined workflows and better organization of your Docker images.