在docker容器内将文件从docker移动到本地

Question

I'm having a python program that stores the output file in local. Now my code is run inside docker container I want to move the generated output file (like output.txt) to my local (outside the docker container)

I know there is a command which transfers files from docker to local:

docker cp <containerId>:/file/path/within/container /host/path/target

#I tried like this inside docker container but it didn't work
os.system(sudo docker cp <containerId>:/file/path/within/container /host/path/target) 

But since my program is executing inside docker this doesn't work and I want to push the file to local as the code runs.

If you have any ideas please share them.

Answer 1

There is no way for code inside a container to directly manipulate anything outside the container. The whole purpose of a container is to isolate it from the host system; breaking this barrier would have grave security consequences, and basically render containers pointless.

What you can do is mount a directory from the host inside the container with -v (or run docker cp from outside the container once you are confident it has succeeded in creating the file successfully; but then how would you communicate this fact to the outside?)

With

docker run --volume=`pwd`:/app myimage

you can

cp myfile /app

inside the container; this will create ./myfile from within Docker.

Answer 2

Treat container as a Linux system, your question will consider as: how transfer files between two hosts.

Maybe there are some another ways without rerun the container:

• scp （recommend） with other options or tools while you need, like expect could handle the ssh 's accept fingerprint or input the password , assume 172.17.0.1 is the host's docker interface and ssh_port is 22 by default, and the ssh progress is listening the docker interface such as 0.0.0.0:22 .

os.system(sudo scp /file/path/within/container user@172.17.0.1:/host/path/target)

• other client–server models, such as rsync (client and server), python SimpleHTTPServer (server) and curl | python request | wget (client) and so on. But these are not recommend, because the server and client need to deploy.