How to copy things in a Docker container

In recent years, Docker containers have become more and more widely used. They can package applications in the form of containers to facilitate porting to different environments. But in some scenarios, we may need to copy the data or code in the Docker container. This article will introduce how to copy the things in the Docker container.

Data and code in Docker containers

In some scenarios, we need to copy the data or code in the container to facilitate various needs such as backup, migration, and debugging. In Docker, data and code are mainly stored in the file system of the container. Different containers are isolated from each other and therefore cannot be copied directly. Data and code need to be copied to the host through some commands. Two common methods are introduced below:

1. Use the docker cp command to copy data

The docker cp command can copy local files into the container, and you can also copy the files in the container to the local. The following is how to use this command:

docker cp : 

Among them, <container id or name></container> indicates that copying is required The ID or name of the container, <path within the container></path> indicates the file path within the container that needs to be copied, <host path></host> indicates the file that needs to be copied to Host path.

For example, copy the /etc/nginx/nginx.conf file in the container nginx to the /opt directory of the host:

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

2. Use the docker commit command to create an image

Use the docker commit command to package the file system in the container into a new image. The specific usage method is as follows:

docker commit -m "commit message"  

Among them, the -m option indicates the description of this commit operation. <container id or name></container> indicates the ID or name of the container that needs to be packaged into an image, <new image name></new> indicates the name of the new image generated.

For example, package the file system in the container nginx into a new image:

docker commit -m "backup nginx config" nginx nginx-config-backup

Summary

Copying the data and code in the Docker container is This article introduces how to implement common requirements in daily work from two aspects:

1. Use the docker cp command to copy the files in the container to the local machine to facilitate backup and debugging.
2. Use the docker commit command to package the file system in the container into a new image to facilitate migration and backup.

Both of the above two methods can realize the need to copy the data and code in the container. You can choose the appropriate method according to the actual situation.

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