Ooooh that shell, Can't you shell that shell

Staying up late to work on a fun project. Building a custom PXE boot image that will be used to pre-load our servers and get them ready for Puppet management. It has been about eight years since I had built a custom boot image. At that time busybox was my goto for small, powerful environments that needed to run from very small RAM mounted file systems.

BusyBox combines tiny versions of many common UNIX utilities into a single small executable. It provides replacements for most of the utilities you usually find in GNU fileutils, shellutils, etc. The utilities in BusyBox generally have fewer options than their full-featured GNU cousins; however, the options that are included provide the expected functionality and behave very much like their GNU counterparts. BusyBox provides a fairly complete environment for any small or embedded system.

When most distros offer boot images that do little more than boot, or fail to boot; for my systems I used busybox to create a very compact environment that would allow you to perform diagnostics and fix any problems.

As great as busybox was at the time, I found it lacked a lot of compatibilities with even old POSIX systems and scripts. Arguments that you rely on for find, grep and even ls, just were not there. Things have changed; somewhat. Busybox has grown up and is full of new abilities.

Screenshot of "make menuconf" providing the ability
to choose the features to build into the binary.

Ultra minimal docker Node.JS example

This is how to get a minimal docker image with just node and run a simple service.
Docker will automatically download the image for alpine-node if you do not already have it.
Use the run command to create and start the new container.
Use -p to publish the container port 3000 on the host at port 3000 on the IP address of the host.
Use -it to connect interactively to the TTY so you can enter and run commands

docker run -p 3000:3000 -it mhart/alpine-node

Your command line is now inside the docker container.
Edit the code of the service.
Copy and paste the sample code below and save the file.

vi service.js

Run node on the service.

node service.js

Open your web browser to the IP address of your host system using :3000 to set the request port.
You should see the hello message.
Use Ctrl+c to exit node & Ctrl+d to exit the container.

You now have a functional container that is set up to run this simple script.
Use the ls --all command to see the container you built.

docker container ls --all

Use the start command to start the container up again.
Use the container ID you found from the ls command.

docker container start <CONTAINER ID>

Check that the container is running and publishing port 3000.

docker container ls

Use the attach command to re-attach to the container.

docker container attach

Run the node command again.

node service.js

var http = require('http');

var server = http.createServer( function(req, res) {
 if (req.url === '/') {
  res.write("Hello World!");
  res.write("I have been expecting you.");
  res.end();
 }

 if (req.url === '/snarky') {
  res.write("If you code it, it will crash!");
  res.end(); 
 }

});

// Port 3000 on IPv4
server.listen(3000, "0.0.0.0");