Unknown MySQL server host <mysql-service-name>

… and you dont know why because everything seems to be correct.

Then you might have an upgrade problem with mysql because you are reusing an old volume that was created for another mysql version.
This can happen when you use a unspecified tag as mysql:latest (not recommended anyway) and there was a version bump in the official mysql image.
Or you upgraded the mysql container yourself, f.e. from mysql:5.6 to mysql:5.7 and you are reusing the data volume with the mysql files.

When you check the startup logs you might see that mysql container is shutting down after startup because of an error like this:

Can't open the mysql.plugin table. Please run mysql_upgrade to create it.

You can run the upgrade command in the container:

docker exec -it mysql_container_name bash -c "mysql_upgrade -uroot -proot"

Or simply delete the volume and recreate it.
Note: the data will unfortunatly be lost. So better dump the data before deleting the volume and reimport it.
In my case its no problem because im starting a new project anyway.

To delete the volume you can:

docker volume rm <volume id>

Or just delete the data dir:

rm -rf ./data/mysql

Then restart your setup so the mysql container recreates the databases:

docker-compose up

and mysql is working again and the application is able to connect. :)

ERROR: for docker_myproject_phpmyadmin_1 Cannot start service mg_myproject_phpmyadmin: network 15dff95a23808fe9d14b3dae71c0daeaa8b274c90566baa5beff37f3738033b6 not found

For some reason the networks were deleted and docker-compose doesnt automatically recreate networks unless you tell so by forcing docker to recreate containers:

docker-compose up --force-recreate

Solution came from this issue:
https://github.com/docker/compose/issues/5745#issuecomment-370031631

Probably i have to explicitly declare the networks to prevent mixups between projects.
Though i thought this would not be necessary…

Update: Today i would rather use the IntelliJ Database Tool for Sqlite administration.

But since Adminer is a popular hacking target they introduced a feature that does not allow to run adminer without a password, out of the box.
Sqlite database usually runs without password and dang, workaround needed!

So we need to add a plugin to adminer that allows password-less login and extend the official Adminer Docker image to include the plugin.

We add a script that loads the official password-less-login plugin and copy it to the plugins-enabled folder of the Adminer image

login-password-less.php:

<?php
require_once('plugins/login-password-less.php');

/** Set allowed password
 * @param string result of password_hash
 */
return new AdminerLoginPasswordLess(
    $password_hash = password_hash("admin", PASSWORD_DEFAULT)
);

Dockerfile:

FROM adminer
USER root
COPY login-password-less.php /var/www/html/plugins-enabled/login-password-less.php
#USER adminer # we run as root because of permissions problems on db file with the volume

In docker-compose.yml:

version: "3"
services:
  app:
    build: ./php
      - mailcatcher
    volumes:
      - "../:/app:rw"
      - "./php/cli/php.ini:/etc/php/7.3/cli/php.ini:ro"
      - "./php/fpm/php.ini:/etc/php/7.3/fpm/php.ini:ro"

  nginx:
    build: ./nginx
    depends_on:
      - app
    command: /bin/sh -c "nginx -g 'daemon off;'"
    volumes:
      - "..:/app:rw"
      - ./nginx/default.conf:/etc/nginx/conf.d/default.conf:ro
    ports:
      - '8088:80'

  adminer:
    build: ./adminer
    restart: unless-stopped
    volumes:
      - "..:/app:rw"
    ports:
      - 8080:8080

File tree:

• adminer
  – Dockerfile
  – login-password-less.php
• nginx
  …
• php
  …
• docker-compose.yml

Note that since docker-compose.yml version 3 the volumes_from directive was removed in favor of top level volumes to share volumes across images. However this implementation is imho rather weird, so i jut duplicated the volumes declaration in the App container and Adminer container.
Feels rather wrong but thats all i could come up with. Any advice here is welcome.

Now that this is done we can open the Sqlite3 database with the pseudo-password “admin” and manage the database.

After all you could also just copy the one-file Adminer with plugin to the php container and run it from within the php container. Just adjust your Nginx config to allow calling the file directly and take care to not deploy Adminer to live.
There is also a project that bundles the plugin with Adminer to one file: https://github.com/FrancoisCapon/LoginToASqlite3DatabaseWithoutCredentialsWithAdminer/blob/master/build-adminer-4-sqlite3-into-one-file.sh