The “docker commit” command is a feature of Docker that allows users to create a new Docker image based on the changes made to a running container. It provides a convenient way to capture and save modifications made to a container’s file system or configuration as a new reusable image.
The primary purpose of the “docker commit” command is to create custom images by persisting the changes made within a container. When a user makes changes to a container, such as installing new software, modifying files, or configuring settings, they can use the “docker commit” command to capture those changes and create a new image.
To use the “docker commit” command, the user specifies the ID or name of the container they want to commit, along with an optional name and tag for the resulting image. Docker then takes a snapshot of the container’s file system and configuration at the time of the commit and creates a new image based on that snapshot.
It’s important to note that the “docker commit” command captures the container’s current state as a new image, including both the modified files and any additional metadata or configuration changes. However, it does not capture the running processes or any changes made to the container’s networking or storage outside of the file system.
The resulting image from the “docker commit” command can be used to create new containers with the same modifications and configurations. This can be useful in scenarios where users want to create custom images from containers that have been modified or configured to their specific needs. The new image can be shared, published to a registry, or used as a base for further customization.
While “docker commit” provides a convenient way to create images from containers, it is generally recommended to use Dockerfiles and the “docker build” command for image creation in a more controlled and reproducible manner. Dockerfiles offer a declarative approach to defining the desired state of an image, including all the necessary instructions for building the image from scratch. This approach allows for version control, transparency, and easier collaboration.
docker commit Command Examples
1. Create an image from a specific container:
# docker commit container image:tag
2. Apply a CMD Dockerfile instruction to the created image:
# docker commit --change="CMD command" container image:tag
3. Apply an ENV Dockerfile instruction to the created image:
# docker commit --change="ENV name=value" container image:tag
4. Create an image with a specific author in the metadata:
# docker commit --author="author" container image:tag
5. Create an image with a specific comment in the metadata:
# docker commit --message="comment" container image:tag
6. Create an image without pausing the container during commit:
# docker commit --pause=false container image:tag
7. Display help:
# docker commit --help
Summary
In summary, the “docker commit” command allows users to create new Docker images by capturing the changes made to a running container. It provides a way to persist modifications made within a container as a new image, enabling users to customize and reuse container configurations. While “docker commit” can be useful in certain cases, it is generally recommended to use Dockerfiles and the “docker build” command for more controlled and reproducible image creation processes.