How to copy files to docker container

With the rapid development of cloud computing, Docker has become a standard deployment platform for many companies and cloud service providers. When using Docker containers, it is often necessary to transfer files between the host and the container, and this requirement makes copying files a necessary skill. This article will introduce how to copy files to a Docker container.

1. Use the docker cp command

Docker provides a special command docker cp, which can copy files between the host and the container. The specific usage is as follows:

docker cp <src_path> <container_id>:<dest_path>
docker cp <container_id>:<src_path> <dest_path></dest_path></src_path></container_id></dest_path></container_id></src_path>

Among them, <src_path></src_path> and <dest_path></dest_path> represent the source and destination paths respectively, <container_id></container_id> represents the container ID.

For example, to copy the file /home/user/file.txt in the host to the /var/www/ directory in the container, you can execute The following command:

docker cp /home/user/file.txt <container_id>:/var/www/</container_id>

Similarly, if you want to copy the file /var/log/nginx/access.log in the container to the host’s /home/user/ directory, you can execute the following command:

docker cp <container_id>:/var/log/nginx/access.log /home/user/</container_id>

It should be noted that if <dest_path></dest_path> ends with /, it means that the target path is a directory , at this time you need to ensure that the target path exists. If <dest_path></dest_path> does not end with /, it means that the target path is a file. In this case, you need to ensure that the upper directory of the target path exists.

2. Use a shared folder

Another way to copy files to a Docker container is to use a shared folder. The prerequisite for this method is that the host directory needs to be mapped to the inside of the container when creating the container. This mapping can be completed through the -v or --mount option:

docker run -v <host_dir>:<container_dir> <image_name></image_name></container_dir></host_dir>

or

docker run --mount type=bind,source=<host_dir>,target=<container_dir> <image_name></image_name></container_dir></host_dir>

Among them, <host_dir></host_dir> represents the directory in the host, and <container_dir></container_dir> represents the directory in the container. Next, the mapped directory can be used inside the container just like a local directory.

In this case, for the files that need to be transferred, you only need to place them in the mapping directory and you can access them in the container. Similarly, files generated in the container can also be placed in the mapped directory and then accessed and processed on the host.

3. Using Docker Volume

Using Docker Volume is another way to copy files to the Docker container. Similar to shared folders, when creating a container using Docker Volume, you need to mount a host directory into the container. The difference is that this mount action creates a standard volume in the Docker daemon and associates this volume with the directory within the container. This enables efficient file sharing between the host and container without relying on the local file system.

The specific usage is as follows:

docker run -v <volume_name>:<container_dir> <image_name></image_name></container_dir></volume_name>

or

docker run --mount type=volume,source=<volume_name>,target=<container_dir> <image_name></image_name></container_dir></volume_name>

Among them, <volume_name></volume_name> represents the name of the standard volume in the Docker daemon process, <container_dir></container_dir> represents the path in the container. Unlike shared folders, Docker Volumes need to be created and deleted explicitly. It can be done with the following command:

docker volume create <volume_name>
docker volume rm <volume_name></volume_name></volume_name>

Finally, files can be copied between the host and the container with the following command:

docker cp <file_path> <container_id>:<container_dir>
docker cp <container_id>:<container_dir> <file_path></file_path></container_dir></container_id></container_dir></container_id></file_path>

Here,<file_path></file_path> represents the local path, <container_id></container_id> represents the container ID, <container_dir></container_dir> represents the directory in the container.

Conclusion

In the process of using Docker containers, copying files is something we often need to do. This article introduces three methods of copying files to Docker containers, namely using the docker cp command, shared folders and Docker Volume. These methods have their own advantages and disadvantages. In practice, you need to choose the method that best suits you based on your specific needs.

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