How do I copy a file from docker container to host

Question

I don't want to install all the runtimes and libraries on the agents themselves so I am thinking to use docker to build my dependencies on a continuous integration server. To achieve this I would need to copy the build artifacts that are built inside the container back into the host.

How do I do that?

Can anyone help me with this.

Thanks

Answer 1

Here is a way which you can try if you want to copy a file from a container to the host. you can use the below command:

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

Here's an example:

[sam@dev]$ sudo docker cp goofy_roentgen:/out_read.jpg .

Here goofy_roentgen is the name I got from the following command:

[sam@dev]$ sudo docker ps
[sudo] password for jalal:
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                                            NAMES
1b4ad9311e93        bamos/openface      "/bin/bash"         33 minutes ago      Up 33 minutes       0.0.0.0:8000->8000/tcp, 0.0.0.0:9000->9000/tcp   goofy_roentge

I hope it will resolve your query.

Comments

How to copy file from container to host using docker-compose.yaml file. Would you please help me in this

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Hi@Saurav,

You can use the volume parameter in your Docker compose script as shown below.

volumes:
      - /dir/on/host:/var/www/html

It will sync your file form the local system to the container.

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After running the mentioend command md5sum is getting changed with the copied file in host, so how to maintain the checksum after copying the file on host

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Hi@Debashis,

You are trying to copy files from the docker container to the host right. So simply use the docker cp command. But how the checksum is getting changed and why it is required. Can you explain your query a little bit more?

Answer 2

• Instead of using docker run you could achieve this using docker create. 

• The docker create command creates a writeable container layer over the specified image and prepares it for running the specified command. The container ID is then printed to STDOUT. 

• This is similar to docker run -d except the container is never started.

• Try this, you never start the container here:

docker create -ti --name dummy IMAGE_NAME bash
docker cp dummy:/path/to/file /dest/to/file
docker rm -fv dummy