Visesh Rajendraprasad viseshrp

Installing cloud-init on a fresh Raspbian Lite image

This is a work in Progress!

Purpose

This mainly demonstrates my goal of preparing a Raspberry Pi to be provisioned prior to its first boot. To do this I have chosen to use the same cloud-init that is the standard for provisioning servers at Amazon EC2, Microsoft Azure, OpenStack, etc.

I found this to be quite challenging because there is little information available for using cloud-init without a cloud. So, this project also servers as a demonstration for anyone on any version of Linux who may want to install from source, and/or use without a cloud. If you fall into that later group, you probably just want to read the code. It's bash so everything I do, you could also do at the command line. (Even the for loop.)

Stuff I wish I'd known sooner about service workers

I recently had several days of extremely frustrating experiences with service workers. Here are a few things I've since learned which would have made my life much easier but which isn't particularly obvious from most of the blog posts and videos I've seen.

I'll add to this list over time – suggested additions welcome in the comments or via twitter.com/rich_harris.

Use Canary for development instead of Chrome stable

~~Chrome 51 has some pretty wild behaviour related to console.log in service workers. Canary doesn't, and it has a load of really good service worker related stuff in devtools.~~

I really liked @tjvantoll article Handling Failed HTTP Responses With fetch(). The one thing I found annoying with it, though, is that response.statusText always returns the generic error message associated with the error code. Most APIs, however, will generally return some kind of useful, more human friendly message in the body.

Here's a modification that will capture this message. The key is that rather than throwing an error, you just throw the response and then process it in the catch block to extract the message in the body:

fetch("/api/foo")
  .then( response => {
    if (!response.ok) { throw response }
    return response.json()  //we only get here if there is no error
 })

How to add more to Git Bash on Windows

Git for Windows comes bundled with the "Git Bash" terminal which is incredibly handy for unix-like commands on a windows machine. It is missing a few standard linux utilities, but it is easy to add ones that have a windows binary available.

The basic idea is that C:\Program Files\Git\mingw64\ is your / directory according to Git Bash (note: depending on how you installed it, the directory might be different. from the start menu, right click on the Git Bash icon and open file location. It might be something like C:\Users\name\AppData\Local\Programs\Git, the mingw64 in this directory is your root. Find it by using pwd -W). If you go to that directory, you will find the typical linux root folder structure (bin, etc, lib and so on).

If you are missing a utility, such as wget, track down a binary for windows and copy the files to the corresponding directories. Sometimes the windows binary have funny prefixes, so

Docker - How to cleanup (unused) resources

Once in a while, you may need to cleanup resources (containers, volumes, images, networks) ...

delete volumes

// see: https://github.com/chadoe/docker-cleanup-volumes

$ docker volume rm $(docker volume ls -qf dangling=true)

$ docker volume ls -qf dangling=true | xargs -r docker volume rm

	<!DOCTYPE html>
	<html>
	<head>
	<title>Service-worker demo</title>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">


	<script>
	if ( "serviceWorker" in navigator ) {

	# see How to Install Redis Server on CentOS 7 - http://linoxide.com/storage/install-redis-server-centos-7/

	# --- Compiling ---
	$ yum install gcc make tcl
	$ REDIS_VER=3.2.3
	$ wget http://download.redis.io/releases/redis-$REDIS_VER.tar.gz
	$ tar xzvf redis-$REDIS_VER.tar.gz
	$ cd redis-$REDIS_VER
	$ make
	$ make test

	/jslint devel: true, browser: true, es5: true /
	/global Promise /

	function imgLoad(url) {
	'use strict';
	// Create new promise with the Promise() constructor;
	// This has as its argument a function with two parameters, resolve and reject
	return new Promise(function (resolve, reject) {
	// Standard XHR to load an image
	var request = new XMLHttpRequest();

	class FizzBuzz:
	def __init__(self,num):
	self.count(num)

	def count(self,num):
	if num >= 1:
	self.count(num - 1)
	self.fizz_buzz(num)

	def fizz_buzz(self,num):

	// Promise.all is good for executing many promises at once
	Promise.all([
	promise1,
	promise2
	]);

	// Promise.resolve is good for wrapping synchronous code
	Promise.resolve().then(function () {
	if (somethingIsNotRight()) {
	throw new Error("I will be rejected asynchronously!");