Sharing a Folder

When you share a folder, the operating system and running containers can see and consume its files. This is one way in which they can interact.

Caution

When you bind mount a file into a container, you will usually want to bind mount the parent directory/folder. If a bind mount destination does not exist, Docker will create the endpoint as an empty directory rather than a file.

In, Copy the Configuration File with Dockerfile, you created and copied the configuration file to /home/shellhttpd/. Keep the changes because you will share the same folder to see what happens. Edit docker-compose.yml, adding the volumes stanza:

vi shellhttpd/docker-compose.yml

version: '3.2'

services:
  httpd:
    image: hub.foundries.io/<factory>/shellhttpd:latest
#    image: shellhttpd:1.0
    restart: always
    volumes:
      - /var/rootdirs/home/fio/shellhttpd:/home/shellhttpd/
    ports:
      - 8080:${PORT-8080}
    environment:
      MSG: "${MSG-Hello world}"

Above, volumes: is added with the value /var/rootdirs/home/fio/shellhttpd:/home/shellhttpd/. This means that /var/rootdirs/home/fio/shellhttpd from your host machine will be mounted over the container’s /home/shellhttpd folder. The container folder content will be overwritten by the host machine’s. Thus, as the host machine folder is empty, the shellhttpd.conf you copied in the Dockerfile will disappear.

Check your changes, add, commit, and push:

git status
git add shellhttpd/docker-compose.yml
git commit -m "Adding shared folder"
git push

Make sure you received your update by checking the latest Target on the Devices tab in your Factory.

Open a terminal connected to your device and check the running containers:

docker ps

CONTAINER ID   IMAGE                               COMMAND                  CREATED          STATUS          PORTS                    NAMES
a2d425490201   hub.foundries.io/<factory>/shellhttpd   "/usr/local/bin/http…"   20 minutes ago   Up 20 minutes   0.0.0.0:8080->8080/tcp   shellhttpd_httpd_1

Monitor the docker logs:

docker logs --follow shellhttpd_httpd_1

PORT=8080
MSG=Hello world

Open a second terminal connected to your device and check for /var/rootdirs/home/fio/shellhttpd:

ls /var/rootdirs/home/fio/shellhttpd/

The folder is empty and was automatically created when the Docker image was launched. Create a new configuration file inside that folder and follow the logs from the first terminal:

sudo bash -c 'echo -e "MSG=\"Hello from shared folder\"" > /var/rootdirs/home/fio/shellhttpd/shellhttpd.conf'

In the first terminal you should see the new MSG value:

PORT=8080
MSG=Hello from shared folder

To confirm the change, test the container from an external device connected to the same network, such as your computer.

curl <device IP>:8080

Hello from shared folder

You have now seen how to share a folder with the container and how to manually update the configuration while the container is running.