There are some situation where you want to copy files to and from a docker container so that we will have data accessabile in host system or within the container.
This can be achieved through multiple ways as listed below.
- Through docker cp command
- Through docker volumes
We will learn these two methods with some examples and explanations.
How to use docker cp command
Syntax:
Usage: docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH
docker cp [OPTIONS] SRC_PATH CONTAINER:DEST_PATH
So ‘docker cp’ command is similar to scp command.
Example: For copying a file(in this case a chef-server deb file) from the container we can use below command
First list available docker containers in your host:
docker ps
Note: We can not retrieve files from a dead/exited docker container, your docker container need to be in running state.
Example output of “docker ps”
SurendraAnneMacBook-Pro:docker-chef-server surendraanne$ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 08a50f4ba59d docker_chef-server "/bin/bash" 4 seconds ago Up 2 seconds 443/tcp, 2223/tcp bold_bell 93ef537a4e79 docker_chef-workstation:latest "/usr/sbin/sshd -D" 11 hours ago Up 11 hours 2224/tcp chef_workstation 27c20adf1c39 docker_chef-node:latest "/usr/sbin/sshd -D" 11 hours ago Up 11 hours 2222/tcp chef_node 02d9a3f04162 docker-chef-server_chef-server:latest "/opt/opscode/embedd…" 11 hours ago Up 11 hours 80/tcp, 0.0.0.0:443->443/tcp chef_server
So my docker container is docker_chef-server and the file is chef-server* is located in /
Docker cp example to copy file from container to host machine.
SurendraAnneMacBook-Pro:docker-chef-server surendraanne$ docker cp 08a50f4ba59d:/chef-server-core_13.1.13-1_amd64.deb . SurendraAnneMacBook-Pro:docker-chef-server surendraanne$ ls CHANGELOG.md backup.sh docker-compose.yml knife.rb Dockerfile chef-server-core_13.1.13-1_amd64.deb init.rb logrotate README.md chef-server.rb install.sh SurendraAnneMacBook-Pro:docker-chef-server surendraanne$ =
Copy files using docker volumes
Docker volumes is nothing but a share between host machine and docker contain for persistent data. This is heavily used to make data persistent across container life cycle. If you have docker volumes attached to a container we can just use cp command to copy files from docker containers.
See if your container have volumes attached, we can use below.
Step1: Get container ID from ps from where you want to get file. This id is useful for inspecting the docker container properties.
docker ps
Output:
SurendraAnneMacBook-Pro:~ surendraanne$ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES da59c665589c ubuntu "/bin/bash" 44 seconds ago Up 43 seconds dazzling_wilbur 44ffd285a7a2 e3d0057c0316 "/bin/bash" 5 months ago Up 2 minutes 80/tcp, 443/tcp infallible_cohen Now get the mount point details from the container ID. SurendraAnneMacBook-Pro:~ surendraanne$ docker inspect -f "{{ .Mounts }}" da59c665589c [{bind /Users/surendraanne/mymount /root/test true rprivate}]
From the above output I can say my local folder which is mounted on docker is /Users/surendraanne/mymount.
To copy a file from docker container location /root/test, we have to just copy from my local directory/Users/surendraanne/mymount on host machine.
Output:
SurendraAnneMacBook-Pro:mymount surendraanne$ pwd /Users/surendraanne/mymount SurendraAnneMacBook-Pro:mymount surendraanne$ ls -l total 0 -rw-r--r-- 1 surendraanne staff 0 30 Jun 22:06 abc -rw-r--r-- 1 surendraanne staff 0 30 Jun 22:07 xyz SurendraAnneMacBook-Pro:mymount surendraanne$
Please share if you know any other methods to copy files to and from docker container
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