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Flow of the python script:

  • I want to run docker image from python script.
  • After running docker image, I need to execute a shell script which creates a tar file inside docker container.
  • I need to copy that tar file to host machine from docker container.
  • and then python script should continue with some stuff to be executed on host machine.

Using docker-py module, I was able to do following:

 pip install docker-py

    docker version
    Client:
     Version:      1.12.1
     API version:  1.24
     Go version:   go1.6.3
     Git commit:   23cf638
     Built:        Thu Aug 18 05:22:43 2016
     OS/Arch:      linux/amd64

    Server:
     Version:      1.12.1
     API version:  1.24
     Go version:   go1.6.3
     Git commit:   23cf638
     Built:        Thu Aug 18 05:22:43 2016
     OS/Arch:      linux/amd64

    >>> import docker

    >>> c = docker.Client(base_url='unix://var/run/docker.sock',version='1.12',timeout=10)

    >>> c.images()
    [{u'Created': 1476217543, u'Labels': {}, u'VirtualSize': 5712315133, u'ParentId': u'sha256:1ba2be8d70b6ede3b68b1af50759e674345236dd952225fcbfbcc1781f370252', u'RepoTags': [u'ubuntu14.04_64:latest'], u'RepoDigests': None, u'Id': u'sha256:1c8ced0fb34d776adafaed938d41a69e3bab87466beaa8752d49bde0d81230c5', u'Size': 5712315133}]

    >>> ctr = c.create_container('ubuntu14.04_64:latest') 

    >>> c.start(ctr)

    docker  ps
    CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
    d685766385e7        ubuntu14.04_64:latest              "bash"              16 hours ago        Up 16 hours                             focused_fermi

    docker images
    REPOSITORY                   TAG                 IMAGE ID            CREATED             SIZE
    ubuntu14.04_64               latest              1c8ced0fb34d        21 hours ago        5.712 GB

I see docker image and container running on host, but now if I want to run shell script inside docker container, how can I do that? after that I need to copy tar from container to host also. Can someone suggest how to do this?

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2 Answers 2

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If you want to run a script in a container you should create a Dockerfile which contains that script. An example might look something like this:

FROM ubuntu14.04_64:latest
COPY ./script.sh /code/script.sh
CMD /code/script.sh -o /target/output.tar.gz

Then your python script would look something like this:

#!/usr/bin/env python
import docker

c = docker.from_env()
c.build('.', image_name)
ctr = c.create_container(image_name, volumes='./target:/target')
c.start(ctr)

# the tarball is now at ./target/output.tar.gz, copy it where you want it
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8 Comments

Thanks for the suggestion, but I need to mount a directory to container from host, so I can't use "CMD" to run script while building docker, I need to run the script while running docker. I tried setting entrypoint in my Dockerfile, I changed workdir in Dockerfile, even though my script is in same path as workdir, I am getting error : no such file or directory.
If somehow I am able to run script by keeping it as an entrypoint in Dockerfile, I will be able to generate tar file in container.
How can I copy tar file which gets generated inside container using python script?
CMD works like ENTRYPOINT, it runs when the container starts, not during build. Don't worry about trying to copy the file out. Use a "host bind mount" (aka bind volume) so that the /target path in the container is actually a directory on the host.
I have added "CMD ./mydir/myshell.sh /repo" in my CMD where "/repo" is mounted from host to container. I ran docker, but dint see tar file getting created from above CMD. This script takes around 3 minutes to generate tar, do I need to include any other commands in Dockerfile?
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This is probably the sequence of commands you want (borrowing from this answer):

docker create --name tmp -it ubuntu14.04_64:latest
docker start tmp
docker exec tmp tar czvf tmp.tgz etc/os-release
docker stop tmp
docker cp tmp:tmp.tgz tmp.tgz
docker rm tmp

Look through this documentation for the equivalent commands with docker-py.

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2 Comments

I have gone through the documentation but couldn't find how can run shell script from container and copy tar from container to host using python.
Using exec shouldn't be necessary here, just set the CMD to the script you want to run.

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