Step 2: Configure Volumes

Table of Contents

• Step 2: Configure Volumes

  • Modify docker-compose.yml Configuring File

  • Start the Project

  • Reset Wordpress Data

Objective: Create volumes that move the data from the container to the host machine. That data is a shared space that both can access, but it resides on the host and not in the container.

Modify docker-compose.yml Configuring File

Now, let’s look at how we can further separate components using Docker. We’ll start with our WordPress project from lab 2 and then modify it.

To start, cd (change directory) to the project directory and create a new docker-compose.yml file.

cd ~                        # Change to your home directory
cd wordpress-docker         # Change to the project directory
nano docker-compose.yml     # Edit the yml file

We’ll start with last week’s project and modify it to include volumes.

Note

YAML syntax is particular about indentations. Verify the number of spaces before the property if you are getting an error.

1. First, let’s change from mysql:5.7 to mariadb.

   MariaDB is a fork of MySQL that is released under the GNU GPL. MySQL is owned by Oracle. The SQL structure of the databases is the same. So, we can simply change the name of the image to use MariaDB instead of MySQL. Pretty cool!

   1. Change image: mysql:5.7 to image: mariadb

   2. Docker will then pull the image from hub.docker.com with tag mariadb, which is this container https://hub.docker.com/_/mariadb/.

2. Next, let’s modify the volume for our database.

   Volumes allow us to keep the data outside of the docker container. The container uses them and has access to the volume data, but the data stay on the host machine. There are some benefits.

   1. First, you have easy access to the data. You can back it up easily.

   2. Then, the containers become disposable. The containers can stop and even be deleted without erasing the data.

      • Starting the project will create new containers and use the same data. By default, Docker stores the volume data within the var folder unless you specify a path.

      • The line - db_data:/var/lib/mysql says the MySQL folder /var/lib/mysql in the container is stored in the folder db-data someplace on the host machine. We want to store this data in our project folder, so let’s modify the path.

      • Change db_data:/var/lib/mysql to ./db_data:/var/lib/mysql

   The ./ in the path tells Docker to use the current directory store db_data, which is our project folder. The project folder always contains the docker-compose.yml file.

3. Then, we want to configure named volumes.

   A named volume allows for volume-specific configurations. We won’t be using them, but we’ll still define them.

4. Next, let’s create volumes for our Wordpress data.

   The Wordpress container stores the HTML data in /var/www/html. We will store this data in a directory called wordpress on the host machine so we can separate it from the container. It also allows us to edit it the Wordpress configuration files easily.

   1. In the wordpress section, create a property called volumes: directly below images.

   2. Create a volume that links wordpress to /var/www/html

   3. Add this line: - ./wordpress:/var/www/html

   4. Add the named value to the volumes section wordpress: {}

   The wordpress section should look like this:

   wordpress:
     depends_on:
       - db
     image: wordpress:latest
     volumes:
       - ./wordpress:/var/www/html
   

5. Exit and save the file.

   Your file should look like this:

   docker-compose.yml

   version: '3.3'
   
   services:
      db:
        image: mariadb:latest
        volumes:
          - ./db_data:/var/lib/mysql
        restart: always
        environment:
          MYSQL_ROOT_PASSWORD: somewordpress
          MYSQL_DATABASE: wordpress
          MYSQL_USER: wordpress
          MYSQL_PASSWORD: wordpress
   
      wordpress:
        depends_on:
          - db
        image: wordpress:latest
        volumes:
          - ./wordpress:/var/www/html
        ports:
          - "20851:80"
        restart: always
        environment:
          WORDPRESS_DB_HOST: db:3306
          WORDPRESS_DB_USER: wordpress
          WORDPRESS_DB_PASSWORD: wordpress
          WORDPRESS_DB_NAME: wordpress
   
   volumes:
       db_data: {}
       wordpress: {}
   

   Note

   On some systems, you need to use a special command for the database to connect. Add the following command below the image:mariabb directive.

   command: --default-authentication-plugin=mysql_native_password

   services:
      db:
        image: mariadb:latest
        command: --default-authentication-plugin=mysql_native_password
        volumes:
          - ./db_data:/var/lib/mysql
   

6. Let’s use docker-compose config to check our config for syntax errors. Refer to the previous lab.

   Expected Output

   root@vps298933:~/wordpress-docker# docker-compose config
   services:
     db:
       environment:
         MYSQL_DATABASE: wordpress
         MYSQL_PASSWORD: wordpress
         MYSQL_ROOT_PASSWORD: somewordpress
         MYSQL_USER: wordpress
       image: mariadb
       restart: always
       volumes:
       - /root/wordpress-docker/db_data:/var/lib/mysql:rw
     wordpress:
       depends_on:
       - db
       environment:
         WORDPRESS_DB_HOST: db:3306
         WORDPRESS_DB_NAME: wordpress
         WORDPRESS_DB_PASSWORD: wordpress
         WORDPRESS_DB_USER: wordpress
       image: wordpress:latest
       ports:
       - published: 20851
         target: 80
       restart: always
       volumes:
       - /root/wordpress-docker/wordpress:/var/www/html:rw
   version: '3.3'
   volumes:
     db_data: {}
     wordpress: {}
   

Start the Project

1. Now, start the project. Verify that you do not have any errors.

   docker-compose up -d
   

   Output

   root@vps298933:~/wordpress-docker# docker-compose up -d
   Creating network "wordpressdocker_default" with the default driver
   Creating volume "wordpressdocker_db-data" with default driver
   Creating volume "wordpressdocker_apache" with default driver
   Creating volume "wordpressdocker_wordpress" with default driver
   Pulling db (mariadb:latest)...
   latest: Pulling from library/mariadb
   898c46f3b1a1: Pull complete
   63366dfa0a50: Pull complete
   041d4cd74a92: Pull complete
   6e1bee0f8701: Pull complete
   0fa9bfc0c84b: Pull complete
   8e9b088fe106: Pull complete
   af96bccda5c4: Pull complete
   0655ee57b408: Pull complete
   58e50a9049b1: Pull complete
   57cd7839e491: Pull complete
   067ff7ef6a22: Pull complete
   895af18c21d0: Pull complete
   1ab4788d5ff4: Pull complete
   a068a53bcb17: Pull complete
   Digest: sha256:06dd6d6234977e9231567cc00b9a994f467417e0419efd61f356a0018064d3a0
   Status: Downloaded newer image for mariadb:latest
   Creating wordpressdocker_db_1 ...
   Creating wordpressdocker_db_1 ... done
   Creating wordpressdocker_wordpress_1 ...
   Creating wordpress-docker_wordpress_1 ... error
   
   ERROR: for wordpress-docker_wordpress_1  Cannot start service wordpress: driver failed programming external connectivity on endpoint wordpress-docker_wordpress_1 (c2ba3b97faa86bdbdac01342dcb848bea84ea1439be9b1bd378a400bafdbe0c9): Bind for 0.0.0.0:80 failed: port is already allocated
   
   ERROR: for wordpress  Cannot start service wordpress: driver failed programming external connectivity on endpoint wordpress-docker_wordpress_1 (c2ba3b97faa86bdbdac01342dcb848bea84ea1439be9b1bd378a400bafdbe0c9): Bind for 0.0.0.0:80 failed: port is already allocated
   ERROR: Encountered errors while bringing up the project.
   

2. You can fix the errors and try again. First, stop the project. Then, make the changes and then try again!

   docker-compose down        #Stops the project and removes the containers.
   nano docker-compose.yml    # Edit the file
   docker-compose up -d       #Creates and starts the Docker project in daemon mode.
   

   That’s better!

   root@vps298933:~/wordpress-docker# docker-compose up -d
   Creating network "wordpressdocker_default" with the default driver
   Creating volume "wordpressdocker_db_data" with default driver
   Creating volume "wordpressdocker_wordpress" with default driver
   Creating wordpressdocker_db_1 ...
   Creating wordpressdocker_db_1 ... done
   Creating wordpressdocker_wordpress_1 ...
   Creating wordpressdocker_wordpress_1 ... done
   root@vps298933:~/wordpress-docker#
   

3. Look in the directory. You should see the directories that contain the volume data.

   ls -lh              #Lists the files and folders in the 'current' directory
   ls -lh wordpress    #Lists the files and folders in the 'wordpress' directory
   

   Output

   root@vps298933:~/wordpress-docker# ls -lh
   total 12K
   drwxr-xr-x 5      999 root     4.0K Mar 30 10:10 db_data
   -rw-r--r-- 1 root     root      660 Mar 30 10:10 docker-compose.yml
   drwxr-xr-x 5 www-data www-data 4.0K Mar 30 10:10 wordpress
   root@vps298933:~/wordpress-docker#
   root@vps298933:~/wordpress-docker# ls -lh wordpress/
   total 204K
   -rw-r--r--  1 www-data www-data  420 Dec  1  2017 index.php
   -rw-r--r--  1 www-data www-data  20K Jan  2 02:37 license.txt
   -rw-r--r--  1 www-data www-data 7.3K Jan  9 08:56 readme.html
   -rw-r--r--  1 www-data www-data 6.8K Jan 12 12:41 wp-activate.php
   drwxr-xr-x  9 www-data www-data 4.0K Mar 13 06:18 wp-admin
   -rw-r--r--  1 www-data www-data  369 Dec  1  2017 wp-blog-header.php
   -rw-r--r--  1 www-data www-data 2.3K Jan 21 07:34 wp-comments-post.php
   -rw-r--r--  1 www-data www-data 3.1K Mar 29 23:10 wp-config.php
   -rw-r--r--  1 www-data www-data 2.8K Mar 29 23:10 wp-config-sample.php
   drwxr-xr-x  4 www-data www-data 4.0K Mar 13 06:18 wp-content
   -rw-r--r--  1 www-data www-data 3.8K Jan  9 14:37 wp-cron.php
   drwxr-xr-x 19 www-data www-data  12K Mar 13 06:18 wp-includes
   -rw-r--r--  1 www-data www-data 2.5K Jan 16 11:29 wp-links-opml.php
   -rw-r--r--  1 www-data www-data 3.3K Dec  1  2017 wp-load.php
   -rw-r--r--  1 www-data www-data  38K Jan 12 12:41 wp-login.php
   -rw-r--r--  1 www-data www-data 8.3K Dec  1  2017 wp-mail.php
   -rw-r--r--  1 www-data www-data  18K Jan 30 17:01 wp-settings.php
   -rw-r--r--  1 www-data www-data  31K Jan 16 22:51 wp-signup.php
   -rw-r--r--  1 www-data www-data 4.7K Dec  1  2017 wp-trackback.php
   -rw-r--r--  1 www-data www-data 3.0K Aug 17  2018 xmlrpc.php
   root@vps298933:~/wordpress-docker#
   

4. Verify that the Wordpress containers is responding to requests

   curl --head http://localhost:20851
   

   Output

   root@vps298933:~/wordpress-docker# curl --head http://localhost:20851
   HTTP/1.1 302 Found
   Date: Sat, 30 Mar 2019 03:57:16 GMT
   Server: Apache/2.4.25 (Debian)
   X-Powered-By: PHP/7.2.16
   Expires: Wed, 11 Jan 1984 05:00:00 GMT
   Cache-Control: no-cache, must-revalidate, max-age=0
   X-Redirect-By: WordPress
   Location: http://localhost:20851/wp-admin/install.php
   Content-Type: text/html; charset=UTF-8
   
   root@vps298933:~/wordpress-docker#
   

5. Configure Wordpress using the web installer

   1. Open your page in a browser: http://blog.example.com

   2. Proceed through the installer

   3. Finally, log in using the username and password that you just created.

Reset Wordpress Data

Caution

These instructions will reset the Wordpress database and remove any data in the Wordpress directory.

What do you do if your username or password doesn’t work? Destroy the containers and volume data, then run the installer again. :))

1. Stop the project and remove all volume data

   docker-compose down -v   #Stops the project and removes the containers and the volume.
   docker-compose up -d     #Creates and starts the Docker project in daemon mode.
   

   Output

   root@vps298933:~/wordpress-docker# docker-compose down -v
   Stopping wordpressdocker_wordpress_1 ... done
   Stopping wordpressdocker_db_1        ... done
   Removing wordpressdocker_wordpress_1 ... done
   Removing wordpressdocker_db_1        ... done
   Removing network wordpressdocker_default
   Removing volume wordpressdocker_db_data
   Removing volume wordpressdocker_wordpress
   root@vps298933:~/wordpress-docker#
   root@vps298933:~/wordpress-docker# docker ps -a
   CONTAINER ID        IMAGE                COMMAND                  CREATED             STATUS              PORTS                     NAMES
   2175f0a86466        nextcloud            "/entrypoint.sh apac…"   7 days ago          Up 6 days           0.0.0.0:20850->80/tcp     condescending_agnesi
   root@vps298933:~/wordpress-docker#
   root@vps298933:~/wordpress-docker# docker-compose up -d
   Creating network "wordpressdocker_default" with the default driver
   Creating volume "wordpressdocker_db_data" with default driver
   Creating volume "wordpressdocker_wordpress" with default driver
   Creating wordpressdocker_db_1 ...
   Creating wordpressdocker_db_1 ... done
   Creating wordpressdocker_wordpress_1 ...
   Creating wordpressdocker_wordpress_1 ... done
   root@vps298933:~/wordpress-docker#
   root@vps298933:~/wordpress-docker# docker ps
   CONTAINER ID        IMAGE                COMMAND                  CREATED             STATUS              PORTS                     NAMES
   28822cf1444c        wordpress:latest     "docker-entrypoint.s…"   20 seconds ago      Up 19 seconds       0.0.0.0:20851->80/tcp     wordpressdocker_wordpress_1
   cdc959eb5014        mariadb              "docker-entrypoint.s…"   21 seconds ago      Up 20 seconds       3306/tcp                  wordpressdocker_db_1
   2175f0a86466        nextcloud            "/entrypoint.sh apac…"   7 days ago          Up 6 days           0.0.0.0:20850->80/tcp     condescending_agnesi
   root@vps298933:~/wordpress-docker#
   

2. You might have to remove the folders manually if docker-compose does not clear the volume data. If so, use this command

   rm -r db-data && rm -r wordpress  # removes the db-data and wordpress folders