In this article, we will learn the use of the docker build command. You can learn more about docker by referring to these articles.
A docker image is a template or blueprint for containers. It is a sharable package with all the code, required tools, runtime, and dependencies to run that specific code. Containers are based on docker images and concrete running instances of images. Docker is a tool for creating and managing containers.
2. Docker build command
The build command builds an image from a DockerFile in the current directory and a build context. A build’s context is the set of files in the specified path or URL. Later, you can use this image to run a docker container.
The syntax of the build command is:
docker build [options] path | URL
The URL parameter can refer to three kinds of resources:
Git repositories
Pre-packaged tarball contexts
Plain text file
The build process can refer to any of the files in the context. For example, your DockerFile can instruct the build command to use a COPY instruction to reference a file in the context i.e., copies new files or directories from the current build context to the filesystem of the container.
Every container has its own file system.
As soon as you execute the docker build, it loads the build definition by reading the Dockerfile.
A sample Dockerfile:
FROM node:14 WORKDIR /app COPY package.json . RUN npm install COPY . . EXPOSE 3000 CMD [ "node", "app.mjs" ]
Sample docker build output
The last line of the docker build output shows the image SHA256 code which you can use to run a docker instance by using the docker run command.
3. Conclusion
To sum up, we have learned to use the build command to construct docker images.
