Robert Hamel roberthamel

How to use ssh-agent to cache your SSH credentials?

Contributed by Fabien Loudet, Linux SysAdmin at Rosetta Stone

Tired of always having to enter your SSH key passphrase when logging in to remote machines? Here comes ssh-agent. Enter the passphrase once and it will keep it in memory for you

Using ssh-agent in your shell session:

Use curl to get the JSON response for the latest release
Use grep to find the line containing file URL
Use cut and tr to extract the URL
Use wget to download it

curl -s https://api.github.com/repos/jgm/pandoc/releases/latest \
| grep "browser_download_url.*deb" \
| cut -d : -f 2,3 \
| tr -d \" \

Real-time Grid Component with Laravel, Vue.js, Vuex & Socket.io (Google Docs-like Functionality)

Motivation

The exercise of writing this tutorial -- as well as recording it as a screencast -- has helped me better understand the concepts behind a couple of my favorite open source tools. Both the tutorial and screencast will be of personal use in the future as references. If they are of help to others, that will be great too.

I love Google Docs' real-time, multi-user interactive capability, and I've have always been a fan of spreadsheets. I wanted to see if I could replicate that type of functionality. What I've done is taken the basic Vue.js Grid Component example and altered it a bit so that when a user clicks on a cell, that cell becomes highlighted or "active", not just in the user's browser but in any browser instance cur

A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,

Converting mkv to mp4 with `ffmpeg`

Essentially just copy the existing video and audio stream as is into a new container, no funny business!

The easiest way to "convert" MKV to MP4, is to copy the existing video and audio streams and place them into a new container. This avoids any encoding task and hence no quality will be lost, it is also a fairly quick process and requires very little CPU power. The main factor is disk read/write speed.

With ffmpeg this can be achieved with -c copy. Older examples may use -vcodec copy -acodec copy which does the same thing.

These examples assume ffmpeg is in your PATH. If not just substitute with the full path to your ffmpeg binary.

Single file conversion example

Requirements

Minikube requires that VT-x/AMD-v virtualization is enabled in BIOS. To check that this is enabled on OSX / macOS run:

sysctl -a | grep machdep.cpu.features | grep VMX

If there's output, you're good!

Prerequisites

Deploying Keycloak to AWS

The objective of this guide is to deploy Keycloak to AWS in a minimally complex way for testing and discovery purposes. This means using the standalone build of Keycloak backed with Hibernate H2. The result is not a production ready system. It won't scale, it won't survive significant load, it can't be clustered.

Mostly this Gist is a distillation of the Keycloak Server Installation guide for a specific use case: to spin up a quick and dirty Keycloak instance for testing and experimenting.

Steps

Spin up and configure a Ubuntu AMI
Install and configure Keycloak with an SSL cert

	curl --include \
	--no-buffer \
	--header "Connection: Upgrade" \
	--header "Upgrade: websocket" \
	--header "Host: example.com:80" \
	--header "Origin: http://example.com:80" \
	--header "Sec-WebSocket-Key: SGVsbG8sIHdvcmxkIQ==" \
	--header "Sec-WebSocket-Version: 13" \
	http://example.com:80/

	from sqlalchemy import Model, Column, Integer, ForeignKey, String, Text
	from orm_helpers import KeyedListCollection


	class ItemAttribute(Model):
	__tablename__ = 'item_attributes'
	id = Column(Integer, primary_key=True, autoincrement=True)
	item_id = Column(Integer, ForeignKey('items.id'))
	attribute = Column(String(255))
	value = Column(Text)

	package firebase;

	public class FirebasePushIdGenerator {

	// Modeled after base64 web-safe chars, but ordered by ASCII.
	private final static String PUSH_CHARS = "-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz";

	// Timestamp of last push, used to prevent local collisions if you push twice in one ms.
	private static long LAST_PUSH_TIME = 0L;