Example

Author: Martin Roy

Dockerfile

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+FROM mariadb:latest as builder
+
+# That file does the DB initialization but also runs mysql daemon, by removing the last line it will only init
+RUN ["sed", "-i", "s/exec \"$@\"/echo \"not running $@\"/", "/usr/local/bin/docker-entrypoint.sh"]
+
+# needed for intialization
+ENV MYSQL_ROOT_PASSWORD=root
+
+COPY setup.sql /docker-entrypoint-initdb.d/
+
+# Need to change the datadir to something else that /var/lib/mysql because the parent docker file defines it as a volume.
+# https://docs.docker.com/engine/reference/builder/#volume :
+# Changing the volume from within the Dockerfile: If any build steps change the data within the volume after
+# it has been declared, those changes will be discarded.
+RUN ["/usr/local/bin/docker-entrypoint.sh", "mysqld", "--datadir", "/initialized-db", "--aria-log-dir-path", "/initialized-db"]
+
+FROM mariadb:latest
+
+COPY --from=builder /initialized-db /var/lib/mysql

README.md

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+A prepopulated mysql container ?
+================================
+
+Yeah why not, i like my test faster :D
+
+But how ?
+---------
+
+The mysql/mariadb container image contain an init script that will execute everything in `/docker-entrypoint-initdb.d/`
+
+see `Initializing a fresh instance` @ https://hub.docker.com/_/mariadb/
+
+So let's run this initialization in a multi-stage build and copy the initialized DB in the new image :D
+
+(see comments in dockerfile for details of the hack) 
+
+Try it!
+======
+
+Clone this, then...
+
+```
+}> docker build --tag my-prepopulated-image .
+...
+
+}> docker run -d --rm --name my-container my-prepopulated-image
+...
+
+}> docker logs my-container
+
+(there was is initialization here, therefore we win)
+
+2018-06-08 21:15:55 0 [Note] mysqld (mysqld 10.3.7-MariaDB-1:10.3.7+maria~jessie) starting as process 1 ...
+2018-06-08 21:15:55 0 [Note] InnoDB: Using Linux native AIO
+2018-06-08 21:15:55 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
+2018-06-08 21:15:55 0 [Note] InnoDB: Uses event mutexes
+2018-06-08 21:15:55 0 [Note] InnoDB: Compressed tables use zlib 1.2.8
+2018-06-08 21:15:55 0 [Note] InnoDB: Number of pools: 1
+2018-06-08 21:15:55 0 [Note] InnoDB: Using SSE2 crc32 instructions
+2018-06-08 21:15:55 0 [Note] InnoDB: Initializing buffer pool, total size = 256M, instances = 1, chunk size = 128M
+2018-06-08 21:15:55 0 [Note] InnoDB: Completed initialization of buffer pool
+2018-06-08 21:15:55 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
+2018-06-08 21:15:56 0 [Note] InnoDB: 128 out of 128 rollback segments are active.
+2018-06-08 21:15:56 0 [Note] InnoDB: Creating shared tablespace for temporary tables
+2018-06-08 21:15:56 0 [Note] InnoDB: Setting file './ibtmp1' size to 12 MB. Physically writing the file full; Please wait ...
+2018-06-08 21:15:56 0 [Note] InnoDB: File './ibtmp1' size is now 12 MB.
+2018-06-08 21:15:56 0 [Note] InnoDB: 10.3.7 started; log sequence number 1639605; transaction id 39
+2018-06-08 21:15:56 0 [Note] InnoDB: Loading buffer pool(s) from /var/lib/mysql/ib_buffer_pool
+2018-06-08 21:15:56 0 [Note] Plugin 'FEEDBACK' is disabled.
+2018-06-08 21:15:56 0 [Note] Server socket created on IP: '::'.
+2018-06-08 21:15:56 0 [Warning] 'proxies_priv' entry '@% root@9977cc179be0' ignored in --skip-name-resolve mode.
+2018-06-08 21:15:56 0 [Note] InnoDB: Buffer pool(s) load completed at 180608 21:15:56
+2018-06-08 21:15:56 0 [Note] Reading of all Master_info entries succeded
+2018-06-08 21:15:56 0 [Note] Added new Master_info '' to hash table
+2018-06-08 21:15:56 0 [Note] mysqld: ready for connections.
+Version: '10.3.7-MariaDB-1:10.3.7+maria~jessie' socket: '/var/run/mysqld/mysqld.sock' port: 3306 mariadb.org binary distribution
+
+}> docker run -it --rm --link my-container mariadb:latest mysql -hmy-container -uroot -proot myexample -e "select * from mytable;"
++---------+
+| myfield |
++---------+
+| Hello |
+| Dolly |
++---------+
+```

setup.sql

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+CREATE DATABASE myexample;
+
+USE myexample;
+
+CREATE TABLE mytable (myfield VARCHAR(20));
+
+INSERT INTO mytable VALUES ('Hello'), ('Dolly');