Let’s talk about how to modify files in Docker

Docker is a popular containerization technology that can easily package, deploy and run applications, and is especially suitable for transfer between development, testing and production environments. In Docker, how to modify the files in the packaged container? This article will guide you to learn how to modify files in Docker.

1. Using the command line in the Docker container

With Dockerfile and Docker image, we can use the following command to open the command line of a Docker container:

docker run -it 镜像名 /bin/bash

This command will open a bash terminal in the container and connect us to the terminal. At this time, you can modify the file in the container.

For example, if you want to modify the /etc/nginx/nginx.conf file in the container, you can use the following command to enter the vim editor and start editing it:

vi /etc/nginx/nginx.conf

After editing is completed, you can use The :wq command will save the changes. In this way we can successfully modify files in the Docker container.

Of course, if we need to perform complex modification operations in the container, we can also use other text editors, such as nano, emacs, etc.

2. Use Docker’s COPY command

Docker’s COPY command can copy local files to the Docker container to modify the files.

The following is a sample Dockerfile, which uses the COPY command:

FROM nginx
COPY nginx.conf /etc/nginx/

This Dockerfile copies the local nginx.conf file to the /etc/nginx/ directory in the Docker container. In this way, we can replace the nginx.conf file in the container with a local file.

When a file changes in the container, you can also use this command to copy the changed file from the container to the host.

For example, the following command copies the file /etc/nginx/nginx.conf in the container to the local /opt/nginx/ directory:

docker cp 容器名:/etc/nginx/nginx.conf /opt/nginx/nginx.conf

This completes the removal from the Docker container The operation of copying files to local.

3. Use Docker’s ADD command

Similar to the COPY command, Docker’s ADD command can also add local files to the Docker container. The ADD command also supports many additional features, such as decompressing and decompressing files.

The following is a sample Dockerfile, which uses the ADD command:

FROM nginx
ADD nginx.conf.gz /etc/nginx/

This Dockerfile adds the local nginx.conf.gz compressed file to the /etc/nginx/ directory in the Docker container , and decompress when added.

4. Use Docker’s VOLUME command

Sometimes, modifying files in a Docker container is not the best choice. In a high-availability environment, we may want to share files among multiple Docker containers or persist file changes after the container is shut down.

In this case, Docker’s VOLUME command can come in handy. The VOLUME command can create a mount point between the local host directory and the Docker container and persist file changes in the container.

The following is a sample Dockerfile, which uses the VOLUME command:

FROM nginx
VOLUME /usr/share/nginx/html

This Dockerfile creates a mount point and places the host directory /usr/share/nginx/html with the same name in the Docker container Directories are connected. Docker retains all changes in the host directory when the container is shut down.

Summary

The above is the method of modifying files in Docker, using the command line, COPY command, ADD command and VOLUME command in the Docker container.

Of course, this is not a complete list of all methods, and there are cases where other methods are used. But these methods are very commonly used, especially during debugging and development.

No matter which method you use, you need to use caution to ensure that you don't cause any damage. If you are not familiar with Docker's file modification operations, please first have a basic understanding of the container packaging and building process. Hope this article helps you!

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