Unable to run mariadb when mount volume - docker

Question

Using the following docker-compose.yml file
version: '2'
services:
wordpress:
image: wordpress
ports:
- 8080:80
environment:
WORDPRESS_DB_NAME: my_db
WORDPRESS_DB_USER: root
WORDPRESS_DB_PASSWORD: password
volumes:
- ./src:/var/www/html
mysql:
image: mariadb
environment:
MYSQL_ROOT_PASSWORD: password
volumes:
- ./data_dir:/var/lib/mysql
when running docker-compose up commande,its giving me following error
Starting wp_mysql_1
Starting wp_wordpress_1
Attaching to wp_mysql_1, wp_wordpress_1
wordpress_1 |
wordpress_1 | Warning: mysqli::mysqli(): (HY000/2002): Connection refused in - on line 19
wordpress_1 |
wordpress_1 | MySQL Connection Error: (2002) Connection refused
mysql_1 | 2016-11-28 15:47:02 139858949081024 [Note] mysqld (mysqld 10.1.19-MariaDB-1~jessie) starting as process 1
...
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] InnoDB: Using mutexes to ref count buffer pool pages
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] InnoDB: The InnoDB memory heap is disabled
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory
barrier
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] InnoDB: Compressed tables use zlib 1.2.8
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] InnoDB: Using Linux native AIO
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] InnoDB: Using SSE crc32 instructions
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] InnoDB: Initializing buffer pool, size = 256.0M
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] InnoDB: Completed initialization of buffer pool
mysql_1 | 2016-11-28 15:47:03 139858949081024 [ERROR] InnoDB: auto-extending data file ./ibdata1 is of a different
size 0 pages (rounded down to MB) than specified in the .cnf file: initial 768 pages, max 0 (relevant if non-zero) pages
!
mysql_1 | 2016-11-28 15:47:03 139858949081024 [ERROR] InnoDB: Could not open or create the system tablespace. If yo
u tried to add new data files to the system tablespace, and it failed here, you should now edit innodb_data_file_path in
my.cnf back to what it was, and remove the new ibdata files InnoDB created in this failed attempt. InnoDB only wrote th
ose files full of zeros, but did not yet use them in any way. But be careful: do not remove old data files which contain
your precious data!
mysql_1 | 2016-11-28 15:47:03 139858949081024 [ERROR] Plugin 'InnoDB' init function returned error.
mysql_1 | 2016-11-28 15:47:03 139858949081024 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
mysql_1 | 2016-11-28 15:47:03 139858949081024 [Note] Plugin 'FEEDBACK' is disabled.
mysql_1 | 2016-11-28 15:47:03 139858949081024 [ERROR] Could not open mysql.plugin table. Some plugins may be not lo
aded
mysql_1 | 2016-11-28 15:47:03 139858949081024 [ERROR] Unknown/unsupported storage engine: InnoDB
mysql_1 | 2016-11-28 15:47:03 139858949081024 [ERROR] Aborting
mysql_1 |
wp_mysql_1 exited with code 1
wordpress_1 |
wordpress_1 | Warning: mysqli::mysqli(): php_network_getaddresses: getaddrinfo failed: Name or service not known in - o
n line 19
wordpress_1 |
wordpress_1 | Warning: mysqli::mysqli(): (HY000/2002): php_network_getaddresses: getaddrinfo failed: Name or service no
t known in - on line 19
wordpress_1 |
wordpress_1 | MySQL Connection Error: (2002) php_network_getaddresses: getaddrinfo failed: Name or service not known
but if I removed the volumes from mysql image, then it works fine! How can I mount the volume as I need data to be persisted.

Answer 1

It's actually a problem with MariaDB. You cannot mount the folder for MariaDB to the host using Docker because it presents the shared files/folders permissions to the database container as root owned with writable only by root. The solution is to use docker-compose named volumes. As stated in docker documentation:
Docker has two options for containers to store files in the host machine, so that the files are persisted even after the container stops: volumes, and bind mounts. If you’re running Docker on Linux you can also use a tmpfs mount.
What you are trying to use is the bind-mount which does not works with MariaDB. So we can use docker volume for that.
When you create a volume, it is stored within a directory on the Docker host. When you mount the volume into a container, this directory is what is mounted into the container. This is similar to the way that bind mounts work, except that volumes are managed by Docker and are isolated from the core functionality of the host machine. Volumes are stored in a part of the host filesystem which is managed by Docker(/var/lib/docker/volumes/ on Linux). So change your docker-compose file as:-
version: '2'
services:
wordpress:
image: wordpress
ports:
- 8080:80
environment:
WORDPRESS_DB_NAME: my_db
WORDPRESS_DB_USER: root
WORDPRESS_DB_PASSWORD: password
volumes:
- ./src:/var/www/html
mysql:
image: mariadb
environment:
MYSQL_ROOT_PASSWORD: password
volumes:
- db_data:/var/lib/mysql
volumes:
db_data:
i.e. use a named volume under mysql service and declare it in top level volumes key. This will tell docker-compose to create a Docker mananged volume and your MariaDB data is backed up/persisted at /var/lib/docker/volumes/_db_data/_data directory on host machine.
Also after running docker-compose up command if you do
docker volume ls
then you can see docker-compose created volume.