Episode 349

Entropy Overhaul


May 7th, 2020

57 mins 33 secs

Your Hosts

About this Episode

Encrypted Crash Dumps in FreeBSD, Time on Unix, Improve ZVOL sync write performance with a taskq, central log host with syslog-ng, NetBSD Entropy overhaul, Setting Up NetBSD Kernel Dev Environment, and more.


EKCD - Encrypted Crash Dumps in FreeBSD

Some time ago, I was describing how to configure networking crash dumps. In that post, I mentioned that there is also the possibility to encrypt crash dumps. Today we will look into this functionality. Initially, it was implemented during Google Summer of Code 2013 by my friend Konrad Witaszczyk, who made it available in FreeBSD 12. If you can understand Polish, you can also look into his presentation on BSD-PL on which he gave a comprehensive review of all kernel crash dumps features.

The main issue with crash dumps is that they may include sensitive information available in memory during a crash. They will contain all the data from the kernel and the userland, like passwords, private keys, etc. While dumping them, they are written to unencrypted storage, so if somebody took out the hard drive, they could access sensitive data. If you are sending a crash dump through the network, it may be captured by third parties. Locally the data are written directly to a dump device, skipping the GEOM subsystem. The purpose of that is to allow a kernel to write a crash dump even in case a panic occurs in the GEOM subsystem. It means that a crash dump cannot be automatically encrypted with GELI.

Time on Unix

Time, a word that is entangled in everything in our lives, something we’re intimately familiar with. Keeping track of it is important for many activities we do.

Over millennia we’ve developed different ways to calculate it. Most prominently, we’ve relied on the position the sun appears to be at in the sky, what is called apparent solar time.

We’ve decided to split it as seasons pass, counting one full cycle of the 4 seasons as a year, a full rotation around the sun. We’ve also divided the passing of light to the lack thereof as days, a rotation of the earth on itself. Moving on to more precise clock divisions such as seconds, minutes, and hours, units that meant different things at different points in history. Ultimately, as travel got faster, the different ways of counting time that evolved in multiple places had to converge. People had to agree on what it all meant.

See the article for more

News Roundup

Improve ZVOL sync write performance by using a taskq

A central log host with syslog-ng on FreeBSD - Part 1

syslog-ng is the Swiss army knife of log management. You can collect logs from any source, process them in real time and deliver them to wide range of destinations. It allows you to flexibly collect, parse, classify, rewrite and correlate logs from across your infrastructure. This is why syslog-ng is the perfect solution for the central log host of my (mainly) FreeBSD based infrastructure.

HEADS UP: NetBSD Entropy Overhaul

This week I committed an overhaul of the kernel entropy system. Please let me know if you observe any snags! For the technical background, see the thread on tech-kern a few months ago: https://mail-index.NetBSD.org/tech-kern/2019/12/21/msg025876.html.

Setting Up NetBSD Kernel Dev Environment

I used T_PAGEFLT’s blog post as a reference for setting my NetBSD kernel development environment since his website is down I’m putting down the steps here so it would be helpful for starters.

Beastie Bits


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