Chapter 5

The easiest way to play with volumes is to use the Docker Toolbox as when directly using Docker for Mac or Docker for Windows, then the volumes are stored inside a (somewhat hidden) Linux VM that Docker for Mac/Win uses transparently.

Thus, we suggest the following:

$ docker-machine create --driver virtualbox volume-test
$ docker-machine ssh volume-test

And now that you're inside a Linux VM called volume-test, you can execute the following exercises:

1. To create a named volume run the following command:

 $ docker volume create my-products

2. Execute the following command:

$ docker container run -it --rm \
    -v my-products:/data:ro \
    alpine /bin/sh

3. To get the path on the host for the volume use, for example, this command:

$ docker volume inspect my-products | grep Mountpoint

Which (if using docker-machine and VirtualBox) should result in:

"Mountpoint": "/mnt/sda1/var/lib/docker/volumes/my-products/_data"

Now execute the following command:

$ sudo su
$ cd /mnt/sda1/var/lib/docker/volumes/my-products/_data
$ echo "Hello world" > sample.txt
$ exit

4. Execute the following command:

$ docker run -it --rm -v my-products:/data:ro alpine /bin/sh
# / cd /data
# / cat sample.txt

In another terminal execute:

 $ docker run -it --rm -v my-products:/app-data alpine /bin/sh
 # / cd /app-data
 # / echo "Hello other container" > hello.txt
 # / exit

5. Execute a command such as this:

$ docker container run -it --rm \
    -v $HOME/my-project:/app/data \
    alpine /bin/sh

6. Exit both containers and then back on the host, execute this command:

$ docker volume prune

7. Run the following command:

$ docker system info | grep Version

Which should output something similar to this:

Server Version: 17.09.1-ce
Kernel Version: 4.4.104-boot2docker

If you have been using docker-machine to create and use a Linux VM in VirtualBox, don't forget to clean up after you're done:

$ docker-machine rm volume-test