Posts in Category "tech"

CDPH Digital Vaccine Record

Yesterday, California released their Digital Vaccine Record system for securely verifying residents' COVID-19 vaccination status. I took a look at it and thought I'd write up my findings here. At a high level, the DVR consists of a QR code which contains a cryptographically-signed assertion in JSON Web Token (JWT) format. I'll walk you through how to get one, how to decode it, and what it contains in the rest of this article.

Getting one of the tokens is pretty easy; you just go to the Digital Vaccine Record website and put in your name, date of birth, and the …

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Surprising behavior in GNU tar

Here's a fun game for you: what do you expect to be the state of the filesystem after running the following commands in an empty directory on a Linux system?

$ touch foo:bar
$ tar -cpf foo:bar.tar foo:bar
$ rm foo:bar
$ tar -xpf foo:bar.tar

Do you expect the directory to contain the files foo:bar and foo:bar.tar?

What if I told you that instead the directory would only contain foo:bar.tar and stderr would say

tar (child): Cannot connect to foo: resolve failed

Yep! It turns out that GNU tar, if passed a …

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Etcd, or, why modern software makes me sad

etcd icon

Once upon a time in 2013, there was a tool called etcd which was a really lightweight database written around the Raft consensus algorithm. This tool was originally written in 2013 for a bullshit unsuccessful project called CoreOS Container Linux that was EOL'd several years ago, but that doesn't really matter — etcd was greater than its original use-case. Etcd provided a convenient and simple set of primitives (set a key, get a key, set-only-if-unchanged, watch-for-changes) with a drop-dead simple HTTP API on top of them. I have built a number of tools using etcd as a lightweight consensus store behind …

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Trackballs

It's been about ten years since I've regularly used that most quintessential of post-1984 computer peripherals, the mouse. The last mouse I had was pretty exclusively used for a gaming PC in college and was a Logitech MX5181; since then I've used a variety of input devices. It's been a while since I did any brief reviews of technology on this ostensibly-technology blog, so what the hey, let's do it! In brief, we're going to talk about:

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2020 MacBook Air Impressions

For the past few years, I've been using a one-port 2016 MacBook1 as my personal laptop that I carry with me whenever I am traveling or need to work outside the house. It's been a mixed bag – the size was pretty much perfect and very similar to a thin version of my old 12" PowerBook G4, but the CPU performance was absolutely awful and the battery only lasted about two hours. Also, I was finally bitten by the infamous Butterfly Keyboard Issue and was getting double-entries from my spacebar.

In March, when Apple released the new MacBook Air with …

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systemd

I've had this sitting on my desktop for months and figured I'd post it. No idea where it originally came from.

systemd