File copy of docker container

1. The running container copy method

Use docker cpthe command to copy files from a physical machine to a running Docker container, or to copy files from a Docker container to a physical machine.

For example, to test.txtcopy into mycontainera container /appdirectory , you can use the following command:

Copy files from host to container:

docker cp test.txt mycontainer:/app/test.txt

where test.txtis the local file to copy, mycontaineris the name of the container, and /app/test.txtis the file path of the container.

If you want to copy the files in the Docker container to the physical machine, you can use the following command:

Copy files from the container to the host:

docker cp mycontainer:/app/test.txt test.txt

This command mycontainerimplements /app/test.txtcopying the files in the container to test.txtthe files .

Note that docker cpthe command requires Docker version 1.8 or later to work. In addition, you need to ensure that you have sufficient read and write permissions for the files to be copied.

2. Copy when building dockerfile

In the Dockerfile, you can directly use COPYthe or ADDcommand to copy the local file to the image. The principle is that when Docker builds the image, it will first copy the local file to a temporary directory, and then add the directory to the file system of the image.

When using COPYthe or ADDcommand, the Docker build engine will find the corresponding file or directory from the build context according to the specified source path, and copy it to the target path in the image. If the source path is a directory, the destination path must /end with , or the COPY or ADD operation will fail.

For example, in the following Dockerfile:

FROM nginx:latest 
COPY index.html /usr/share/nginx/html/
ADD static.tar.gz /usr/share/nginx/html/

This Dockerfile specifies nginx:latestas the base image, and then index.htmlcopies the files in the local directory to /usr/share/nginx/html/the directory . When building an image, the Docker build engine will first index.htmlcopy to a temporary directory, and then add the directory to the image's file system, so as to copy files from the local to the image.

Therefore, it is possible to copy local files into the container directly using the COPYor . ADDMoreover, doing so also automates the copying of files into the image, so that the image can be used directly when creating a new container, and there is no need to manually copy the files.