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README.md

Ubuntu Base

FROM quay.io/continuouspipe/ubuntu:16.04

How to build

docker build --pull --tag quay.io/continuouspipe/ubuntu:16.04 --rm .
docker push

How to use

The etc and usr folders local to this README get copied into the image. That means we can influence any file in etc or usr using Docker's layering filesystem.

Upon booting, /bin/bash /usr/local/bin/supervisor_start will run, which will:

  1. Include environment variable definitions from /usr/local/share/env/
  2. Run confd to render templates with environment variables.
  3. Run any custom tasks in /usr/local/bin/supervisor_custom_start
  4. Run supervisord to start services

SupervisorD

We are using supervisord to control service startup and provide a way to handle zombie processes gracefully, with supervisord becoming PID 1.

You can start any service you want by adding a config file into the /etc/supervisor/conf.d folder. For example, to start NGINX, place the following in etc/supervisor/conf.d/nginx.conf:

[program:nginx]
command = /usr/sbin/nginx -g 'daemon off;'
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0
user = root
autostart = true
autorestart = true
priority = 10

ConfD

ConfD is in use to provide templating support for configuration files.

ConfD is automatically run when an image starts, and crucially, it is run before anything else. That means you can have an optional SupervisorD service like so, in `etc/confd/templates/supervisor/nginx.conf:

[program:nginx]
command = /usr/sbin/nginx -g 'daemon off;'
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0
user = root
autostart = {{ getenv "START_NGINX" }}
autorestart = true
priority = 10

This is backed up by the confd configuration file: etc/confd/conf.d/supervisor_nginx.conf:

[template]
src   = "supervisor/nginx.conf.tmpl"
dest  = "/etc/supervisord/conf.d/nginx.conf"
mode  = "0644"
keys = [
]

Default Environment Variables

To define default environment variables, for confd to use when rendering templates, place an export line in usr/local/share/env/default_env_variables for base images, or usr/local/share/env/custom_env_variables for images where you wish to override the defaults.

For example, a default_env_variables:

#!/bin/bash

export PHP_TIMEZONE=${PHP_TIMEZONE:-UTC}
export PHP_MEMORY_LIMIT=${PHP_MEMORY_LIMIT:-256M}
export APP_USER=${APP_USER:-www-data}
export APP_GROUP=${APP_GROUP:-www-data}
export START_NGINX=${START_NGINX:-false}
export START_PHP_FPM=${START_PHP_FPM:-false}

This will use any of the named variables that are defined outside of the container, for example if passed in through docker-compose, they will be used instead of these defaults.

Custom Startup Scripts

To run custom scripts before a service starts, please add usr/local/bin/supervisor_custom_start in your child image and it will automatically be executed before supervisor is started.

Known child images