How to create populated MySQL Docker Image on build time

Question

I would like to create a MySQL Docker image with data already populated.

I want to create 3 layers like this:

        |---------------------|--------         


        

Answer 1

This cannot be done cleanly the exact way you want it to, at least when basing on official mysql image, because you need to communicate with the server to import the data and the server is not run and initialized (from mysql's docker-entrypoint.sh) until the container is run, which is only when the image is already built.

The not-so-clean way is to run the process in the container, using the /entrypoint.sh script from mysql image, but you must take care of all the settings required by the entrypoint (like $MYSQL_ROOT_PASSWORD) as well as a clean way to stop the daemon just after importing the data. Something like:

FROM mysql:5.6

ADD data.sql /docker-entrypoint-initdb.d/00-import-data.sql
ENV MYSQL_ROOT_PASSWORD somepassword
ENV MYSQL_DATABASE db1
RUN /entrypoint.sh mysqld & sleep 30 && killall mysqld

is a hackish way that results in pre-initialized DB, but... it doesn't work. The reason is that /var/lib/mysql is declared as a volume in mysql's Dockerfile, and any changes to this directory during build process are lost after the build step is done. This can be observed in the following Dockerfile:

FROM mysql:5.6

RUN touch /var/lib/mysql/some-file && ls /var/lib/mysql
RUN touch /var/lib/mysql/some-file2 && ls /var/lib/mysql

So I suggest going with docker commit way you described. The end result is the same as the one you want to achieve, with an exception of Layer 2 maybe.

UPDATE: As OP commented below, the commit doesn't contain volumes either. So, the only way seems to be to either edit MySQL Dockerfile and remove VOLUME to keep data inside the container, or to manage the volumes separately from containers.