What are the basic instructions in a Dockerfile?

What are the basic instructions in a Dockerfile?

A Dockerfile is a script with a set of instructions to build a Docker image. The basic instructions include:

1. FROM: Specifies the base image.
2. RUN: Executes commands in the image during the build process.
3. CMD: Provides defaults for an executing container.
4. COPY: Copies files from the host to the image.
5. ADD: Similar to COPY but can also extract compressed files.
6. ENV: Sets environment variables.

Can you explain the difference between RUN and CMD?

Sure! RUN is used to execute commands during the image build process, while CMD specifies the default command to run when a container is started from the image. You can have multiple RUN instructions, but only one CMD.

What is the purpose of the COPY instruction?

The COPY instruction is used to copy files or directories from the host machine into the Docker image. This is essential for including application code or configuration files in the image.

Are there any best practices for writing a Dockerfile?

Yes, some best practices include:

• Use a minimal base image.
• Combine RUN commands to reduce layers.
• Order instructions to leverage caching.
• Use .dockerignore to exclude unnecessary files.