docker: re-run the start script on the container's first run because it won't know its hostname or IP address until then

Dockerfile

@@ -5,10 +5,11 @@
 # To build the image:
 # sudo docker.io build -t box .
 
-# To run a container for testing (with a command prompt and no publicly exposed ports):
-# sudo docker.io run -i -t -P box
+# Run your container the first time with an interactive console so you can
+# create your first mail account.
+# sudo docker.io run -i -t box
 
-# Or to run in the background and expose all of the ports so that the *host* acts as a Mail-in-a-Box:
+# Then run it in the background and expose all of the ports so that the *host* acts as a Mail-in-a-Box:
 # (the SSH port is only available locally, but other ports are exposed publicly and must be available
 # otherwise the container won't start)
 # sudo docker.io run -d -p 22 -p 25:25 -p 53:53/udp -p 443:443 -p 587:587 -p 993:993 box
@@ -18,9 +19,10 @@ MAINTAINER Joshua Tauberer (http://razor.occams.info)
 
 # We can't know these values ahead of time, so set them to something
 # obviously local. The start.sh script will need to be run again once
-# these values are known. 
+# these values are known. We use the IP address here as a flag that
+# the configuration is incomplete.
 ENV PUBLIC_HOSTNAME box.local
-ENV PUBLIC_IP 127.0.123.123
+ENV PUBLIC_IP 192.168.200.1
 
 # Docker-specific Mail-in-a-Box configuration.
 ENV DISABLE_FIREWALL 1

containers/docker/start_services.sh

@@ -1,4 +1,25 @@
 #!/bin/bash
+
+# The PUBLIC_HOSTNAME and PUBLIC_IP is not known at the time the docker
+# image is built. On the first run of the container, re-run the start
+# script with actual values. That will also ask the user for their first
+# email user account.
+if grep "^PUBLIC_IP=192.168.200.1" /etc/mailinabox.conf > /dev/null; then
+  echo "Configuring container on first run..."
+
+  # Get the public IP address of the host machine.
+  export PUBLIC_IP=`curl -s icanhazip.com`
+  echo Your IP address is $PUBLIC_IP.
+
+  # Get the reverse DNS of that IP address.
+  export PUBLIC_HOSTNAME=`host $PUBLIC_IP | sed -e "s/.* //" | sed -e "s/\.$//"`
+  echo Your hostname is $PUBLIC_HOSTNAME.
+
+  # Start configuration again.
+  cd /usr/local/mailinabox
+  scripts/start.sh
+fi
+
 echo "Starting Mail-in-a-Box services..."
 
 service nsd start

scripts/system.sh

@@ -20,7 +20,9 @@ if grep -q "^PasswordAuthentication yes" /etc/ssh/sshd_config \
         exit
 fi
 
-apt_install python3
+# Install basic utilities.
+
+apt_install python3 curl bind9-host
 
 # Turn on basic services:
 #