Copying files from Docker container to host

Question

I\'m thinking of using Docker to build my dependencies on a Continuous Integration (CI) server, so that I don\'t have to install all the runtimes and libraries on the agents

Answer 1

This can also be done in the SDK for example python. If you already have a container built you can lookup the name via console ( docker ps -a ) name seems to be some concatenation of a scientist and an adjective (i.e. "relaxed_pasteur").

Check out help(container.get_archive) :

Help on method get_archive in module docker.models.containers:

get_archive(path, chunk_size=2097152) method of docker.models.containers.Container instance
    Retrieve a file or folder from the container in the form of a tar
    archive.

    Args:
        path (str): Path to the file or folder to retrieve
        chunk_size (int): The number of bytes returned by each iteration
            of the generator. If ``None``, data will be streamed as it is
            received. Default: 2 MB

    Returns:
        (tuple): First element is a raw tar data stream. Second element is
        a dict containing ``stat`` information on the specified ``path``.

    Raises:
        :py:class:`docker.errors.APIError`
            If the server returns an error.

    Example:

        >>> f = open('./sh_bin.tar', 'wb')
        >>> bits, stat = container.get_archive('/bin/sh')
        >>> print(stat)
        {'name': 'sh', 'size': 1075464, 'mode': 493,
         'mtime': '2018-10-01T15:37:48-07:00', 'linkTarget': ''}
        >>> for chunk in bits:
        ...    f.write(chunk)
        >>> f.close()

So then something like this will pull out from the specified path ( /output) in the container to your host machine and unpack the tar.

import docker
import os
import tarfile

# Docker client
client = docker.from_env()
#container object
container = client.containers.get("relaxed_pasteur")
#setup tar to write bits to
f = open(os.path.join(os.getcwd(),"output.tar"),"wb")
#get the bits
bits, stat = container.get_archive('/output')
#write the bits
for chunk in bits:
    f.write(chunk)
f.close()
#unpack
tar = tarfile.open("output.tar")
tar.extractall()
tar.close()