Docker Cookbook

26 | Chapter 1: Getting Started with Docker

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RUN (/usr/bin/mysqld_safe &); sleep 5; mysqladmin -u root -proot create wordpress
COPY wp-config.php /var/www/html/wp-config.php
COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf
EXPOSE 80
CMD ["/usr/bin/supervisord"]
Supervisor is configured via the 
supervisord.conf
file like so:
[supervisord]
nodaemon=true
[program:mysqld]
command=/usr/bin/mysqld_safe
autostart=true
autorestart=true
user=root
[program:httpd]
command=/bin/bash -c "rm -rf /run/httpd/* && /usr/sbin/apachectl -D FOREGROUND"
Two programs are defined to be run and monitored: 
mysqld
and 
httpd
. Each pro‐
gram can use various options like 
autorestart
and 
autostart
. The most important
directive is 
command
, which defines how to run each program. With this configura‐
tion, a Docker container needs to run only a single foreground process: 
supervisord
.
Hence the line in the Dockerfile, 
CMD ["/usr/bin/supervisord"]
.
On your Docker host, build the image and start a background container off of it. If
you are using the Vagrant virtual machine started via the example files, do this:
$ cd /vagrant
$ docker build -t wordpress .
$ docker run -d -p 80:80 wordpress
Port forwarding will be set up between your host and the Docker container for port
80. You will just need to open your browser to 
">http://
and
configure WordPress.
Discussion
Although using Supervisor to run multiple application services in a single container
works perfectly, it is better to use multiple containers. It promotes the isolation of
concerns using containers and helps create a microservices-based design for your
application (see 
Building Microservices
). Ultimately, this will help with scale and resil‐
iency.