Docker best practices

- Install and remove OS and Go build deps in a single layer
- Use COPY instead of ADD
- WORKDIR now resolves ENV variables, use one
- Use VOLUMES for configuration and datastore
- Added launcher script start-inbucket.sh
- Made docker-run.sh more powerful

etc/docker/defaults/greeting.html

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+<p>Inbucket is an email testing service; it will accept email for any email
+address and make it available to view without a password.</p>
+
+<p>To view email for a particular address, enter the username portion
+of the address into the box on the upper right and click <em>View</em>.</p>
+
+<p>This instance of Inbucket is running inside of a <a
+  href="https://www.docker.com/" target="_blank">Docker</a> container.  It is
+configured to retain messages for a maximum of 3 days, and will enforce a limit
+of 300 messages per mailbox - the oldest messages will be deleted to stay under
+that limit.</p>
+
+<p>Messages addressed to any recipient in the <code>@bitbucket.local</code>
+domain will be accepted but not written to disk.  Use this domain for load or
+soak testing your application.</p>

etc/docker/defaults/inbucket.conf

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+# inbucket.conf
+# Configuration for Inbucket inside of Docker
+#
+# These should be reasonable defaults for a production install of Inbucket
+
+#############################################################################
+[DEFAULT]
+
+# Not used directly, but is typically referenced below in %()s format.
+install.dir=/opt/inbucket
+domain=inbucket.local
+
+#############################################################################
+[logging]
+
+# Options from least to most verbose: ERROR, WARN, INFO, TRACE
+level=INFO
+
+#############################################################################
+[smtp]
+
+# IPv4 address to listen for SMTP connections on.
+ip4.address=0.0.0.0
+
+# IPv4 port to listen for SMTP connections on.
+ip4.port=10025
+
+# used in SMTP greeting
+domain=inbucket.local
+
+# optional: mail sent to accounts at this domain will not be stored,
+# for mixed use (content and load testing)
+domain.nostore=bitbucket.local
+
+# Maximum number of RCPT TO: addresses we allow from clients, the SMTP
+# RFC recommends this be at least 100.
+max.recipients=100
+
+# How long we allow a network connection to be idle before hanging up on the
+# client, SMTP RFC recommends at least 5 minutes (300 seconds).
+max.idle.seconds=300
+
+# Maximum allowable size of message body in bytes (including attachments)
+max.message.bytes=2048000
+
+# Should we place messages into the datastore, or just throw them away
+# (for load testing): true or false
+store.messages=true
+
+#############################################################################
+[pop3]
+
+# IPv4 address to listen for POP3 connections on.
+ip4.address=0.0.0.0
+
+# IPv4 port to listen for POP3 connections on.
+ip4.port=10110
+
+# used in POP3 greeting
+domain=%(domain)
+
+# How long we allow a network connection to be idle before hanging up on the
+# client, POP3 RFC requires at least 10 minutes (600 seconds).
+max.idle.seconds=600
+
+#############################################################################
+[web]
+
+# IPv4 address to serve HTTP web interface on
+ip4.address=0.0.0.0
+
+# IPv4 port to serve HTTP web interface on
+ip4.port=10080
+
+# Name of web theme to use
+theme=bootstrap
+
+# Path to the selected themes template files
+template.dir=%(install.dir)s/themes/%(theme)s/templates
+
+# Should we cache parsed templates (set to false during theme dev)
+template.cache=true
+
+# Path to the selected themes public (static) files
+public.dir=%(install.dir)s/themes/%(theme)s/public
+
+# Path to the greeting HTML displayed on front page, can
+# be moved out of installation dir for customization
+greeting.file=/con/configuration/greeting.html
+
+#############################################################################
+[datastore]
+
+# Path to the datastore, mail will be written into subdirectories
+path=/con/data
+
+# How many minutes after receipt should a message be stored until it's
+# automatically purged.  To retain messages until manually deleted, set this
+# to 0
+retention.minutes=4320
+
+# How many milliseconds to sleep after purging messages from a mailbox.
+# This should help reduce disk I/O when there are a large number of messages
+# to purge.
+retention.sleep.millis=100
+
+# Maximum number of messages we will store in a single mailbox. If this
+# number is exceeded, the oldest message in the box will be deleted each
+# time a new message is received for it.
+mailbox.message.cap=300

etc/docker/defaults/start-inbucket.sh

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+#!/bin/sh
+# start-inbucket.sh
+# description: start inbucket (runs within a docker container)
+
+CONF_SOURCE="$INBUCKET_HOME/defaults"
+CONF_TARGET="/con/configuration"
+
+set -eo pipefail
+
+install_default_config() {
+  local file="$1"
+  local source="$CONF_SOURCE/$file"
+  local target="$CONF_TARGET/$file"
+
+  if [ ! -e "$target" ]; then
+    echo "Installing default $file to $CONF_TARGET"
+    install "$source" "$target"
+  fi
+}
+
+install_default_config "inbucket.conf"
+install_default_config "greeting.html"
+
+exec "$INBUCKET_HOME/bin/inbucket" $*