Persistence with Bitnami's Wordpress Docker Setup - wordpress

Question

I'm trying to set up Wordpress with this documentation:
https://github.com/bitnami/bitnami-docker-wordpress#mount-host-directories-as-data-volumes-with-docker-compose
My host directories for the volumes look like this in the docker-compose file:
volumes:
- './mariadb_data:/bitnami'
...
volumes:
- './wordpress_data:/bitnami'
When running docker-compose up, the following errors occur:
mariadb_1 | INFO ==> Starting mysqld_safe...
mariadb_1 | Could not open required defaults file: /opt/bitnami/mariadb/conf/my.cnf
mariadb_1 | Fatal error in defaults handling. Program aborted
mariadb_1 | WARNING: Defaults file '/opt/bitnami/mariadb/conf/my.cnf' not found!
mariadb_1 | Could not open required defaults file: /opt/bitnami/mariadb/conf/my.cnf
mariadb_1 | Fatal error in defaults handling. Program aborted
mariadb_1 | WARNING: Defaults file '/opt/bitnami/mariadb/conf/my.cnf' not found!
mariadb_1 | 171105 05:15:41 mysqld_safe Logging to '/opt/bitnami/mariadb/data/200101d1b330.err'.
mariadb_1 | 171105 05:15:41 mysqld_safe Starting mysqld daemon with databases from /opt/bitnami/mariadb/data
mariadb_1 | /opt/bitnami/mariadb/bin/mysqld_safe_helper: Can't create/write to file '/opt/bitnami/mariadb/data/200101d1b330.err' (Errcode: 2 "No such file or directory")
myproject_mariadb_1 exited with code 1
However, if I change my docker-compose file to use non-host directories:
volumes:
- 'mariadb_data:/bitnami'
...
volumes:
- 'wordpress_data:/bitnami'
... the docker-compose up works.
If I then stop docker, and then revert my docker-compose file to use host directories again, docker-compose up will now work, and the host directories are populated correctly.
This is a solution to my problem, but I would like to know why, and if there is a way to make things work without this work-around.

Answer 1

Check if the bitnami/bitnami-docker-mariadb issue 123 is relevant in your case:
It seems that docker-compose up did not create a container from scratch (with a clean filesystem), but instead used one preexisting. I deduce this from the beginning sequence:
Starting mariadb_mariadb_1
Attaching to mariadb_mariadb_1
...
It seems to me that this container, in its previous execution, was started with an attached volume at /bitnami/mariadb. After that, the container was stopped, such volume detached, and then the container was restarted. It didn't configure anything and just tried to run the mysql server binary. Since we perform symbolic links from /opt/bitnami/mariadb pointing to /bitnami/mariadb (my.cnf file included), that file went missing and the binaries crashed at start time.
Could you please try using the docker-compose file we provide in this repo? If you only modify it for adding environment variables you shouldn't run into these kind of issues.
As a workaround, just run the following:
docker-compose down -v
docker-compose up
It will remove the the MariaDB container, along with any volume associated, and start from scratch. Bear in mind that you will lose any state you set in the container.