DockerCLI/man/src/container/cp.md

The docker container cp utility copies the contents of SRC_PATH to the DEST_PATH. You can copy from the container's file system to the local machine or the reverse, from the local filesystem to the container. If - is specified for either the SRC_PATH or DEST_PATH, you can also stream a tar archive from STDIN or to STDOUT. The CONTAINER can be a running or stopped container. The SRC_PATH or DEST_PATH can be a file or directory.

The docker container cp command assumes container paths are relative to the container's / (root) directory. This means supplying the initial forward slash is optional; The command sees compassionate_darwin:/tmp/foo/myfile.txt and compassionate_darwin:tmp/foo/myfile.txt as identical. Local machine paths can be an absolute or relative value. The command interprets a local machine's relative paths as relative to the current working directory where docker container cp is run.

The cp command behaves like the Unix cp -a command in that directories are copied recursively with permissions preserved if possible. Ownership is set to the user and primary group at the destination. For example, files copied to a container are created with UID:GID of the root user. Files copied to the local machine are created with the UID:GID of the user which invoked the docker container cp command. If you specify the -L option, docker container cp follows any symbolic link in the SRC_PATH. docker container cp does not create parent directories for DEST_PATH if they do not exist.

Assuming a path separator of /, a first argument of SRC_PATH and second argument of DEST_PATH, the behavior is as follows:

• SRC_PATH specifies a file
  • DEST_PATH does not exist
    • the file is saved to a file created at DEST_PATH
  • DEST_PATH does not exist and ends with /
    • Error condition: the destination directory must exist.
  • DEST_PATH exists and is a file
    • the destination is overwritten with the source file's contents
  • DEST_PATH exists and is a directory
    • the file is copied into this directory using the basename from SRC_PATH
• SRC_PATH specifies a directory
  • DEST_PATH does not exist
    • DEST_PATH is created as a directory and the contents of the source directory are copied into this directory
  • DEST_PATH exists and is a file
    • Error condition: cannot copy a directory to a file
  • DEST_PATH exists and is a directory
    • SRC_PATH does not end with /. (that is: slash followed by dot)
      • the source directory is copied into this directory
    • SRC_PATH does end with /. (that is: slash followed by dot)
      • the content of the source directory is copied into this directory

The command requires SRC_PATH and DEST_PATH to exist according to the above rules. If SRC_PATH is local and is a symbolic link, the symbolic link, not the target, is copied by default. To copy the link target and not the link, specify the -L option.

A colon (:) is used as a delimiter between CONTAINER and its path. You can also use : when specifying paths to a SRC_PATH or DEST_PATH on a local machine, for example file:name.txt. If you use a : in a local machine path, you must be explicit with a relative or absolute path, for example:

`/path/to/file:name.txt` or `./file:name.txt`

It is not possible to copy certain system files such as resources under /proc, /sys, /dev, tmpfs, and mounts created by the user in the container. However, you can still copy such files by manually running tar in docker exec. For example (consider SRC_PATH and DEST_PATH are directories):

$ docker exec foo tar Ccf $(dirname SRC_PATH) - $(basename SRC_PATH) | tar Cxf DEST_PATH -

or

$ tar Ccf $(dirname SRC_PATH) - $(basename SRC_PATH) | docker exec -i foo tar Cxf DEST_PATH -

Using - as the SRC_PATH streams the contents of STDIN as a tar archive. The command extracts the content of the tar to the DEST_PATH in container's filesystem. In this case, DEST_PATH must specify a directory. Using - as the DEST_PATH streams the contents of the resource as a tar archive to STDOUT.

EXAMPLES

Suppose a container has finished producing some output as a file it saves to somewhere in its filesystem. This could be the output of a build job or some other computation. You can copy these outputs from the container to a location on your local host.

If you want to copy the /tmp/foo directory from a container to the existing /tmp directory on your host. If you run docker container cp in your ~ (home) directory on the local host:

$ docker container cp compassionate_darwin:tmp/foo /tmp

Docker creates a /tmp/foo directory on your host. Alternatively, you can omit the leading slash in the command. If you execute this command from your home directory:

$ docker container cp compassionate_darwin:tmp/foo tmp

If ~/tmp does not exist, Docker will create it and copy the contents of /tmp/foo from the container into this new directory. If ~/tmp already exists as a directory, then Docker will copy the contents of /tmp/foo from the container into a directory at ~/tmp/foo.

When copying a single file to an existing LOCALPATH, the docker container cp command will either overwrite the contents of LOCALPATH if it is a file or place it into LOCALPATH if it is a directory, overwriting an existing file of the same name if one exists. For example, this command:

$ docker container cp sharp_ptolemy:/tmp/foo/myfile.txt /test

If /test does not exist on the local machine, it will be created as a file with the contents of /tmp/foo/myfile.txt from the container. If /test exists as a file, it will be overwritten. Lastly, if /test exists as a directory, the file will be copied to /test/myfile.txt.

Next, suppose you want to copy a file or folder into a container. For example, this could be a configuration file or some other input to a long running computation that you would like to place into a created container before it starts. This is useful because it does not require the configuration file or other input to exist in the container image.

If you have a file, config.yml, in the current directory on your local host and wish to copy it to an existing directory at /etc/my-app.d in a container, this command can be used:

$ docker container cp config.yml myappcontainer:/etc/my-app.d

If you have several files in a local directory /config which you need to copy to a directory /etc/my-app.d in a container:

$ docker container cp /config/. myappcontainer:/etc/my-app.d

The above command will copy the contents of the local /config directory into the directory /etc/my-app.d in the container.

Finally, if you want to copy a symbolic link into a container, you typically want to copy the linked target and not the link itself. To copy the target, use the -L option, for example:

$ ln -s /tmp/somefile /tmp/somefile.ln
$ docker container cp -L /tmp/somefile.ln myappcontainer:/tmp/

This command copies content of the local /tmp/somefile into the file /tmp/somefile.ln in the container. Without -L option, the /tmp/somefile.ln preserves its symbolic link but not its content.