How to run a command after creating a container using yml file - docker

Question

I have very limited experience with Docker, and having an issue, so I have the following yml file:
version: '2'
services:
python:
restart: always
build: .path/to/docker/file
ports:
- "5000:5000"
- "8888:8888"
links:
- db
depends_on:
- db
volumes:
- ./path/to/file/:/app:z
entrypoint:
- python
- -u
- /app/run.py
db:
image: mysql:latest
environment:
MYSQL_ROOT_PASSWORD: xxyyzz
MYSQL_DATABASE: database_name
MYSQL_USER: user_name
MYSQL_PASSWORD: xxyyzz
volumes:
- ./Dump.sql:/db/Dump.sql:z
- ./Dump_Test.sql:/db/Dump_Test.sql:z
- ./big_fc.sql:/db/big_fc.sql:z
ports:
- "3306:3306"
I need to run the following commands for the second container db:
echo '[mysqld]' >> /etc/mysql/conf.d/mysql.cnf
echo 'sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION' >> /etc/mysql/conf.d/mysql.cnf
The point is that I want to run these commands just once as when you provide a docker file for the first container python. How can I achieve this?

Answer 1

My first advice is to build your own image with your own Dockerfile. In this case you will do it once and all the containers will have the same config.
Dockerfile should look like this:
FROM mysql:latest
COPY create_config.sh /tmp/create_config.sh
CMD ["/tmp/create_config.sh"]
Create create_config.sh in the same dir as your Dockerfile and put your required commands there:
#!/bin/bash
echo '[mysqld]' >> /etc/mysql/conf.d/mysql.cnf
echo 'sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION' >> /etc/mysql/conf.d/mysql.cnf
Now you can use it in your docker-compose.yml:
db:
context: .
dockerfile: Dockerfile
Keep in mind, that context is the path to the dir where your new Dockerfile is.