RSS Parrot

FOSDEM 2026 Talks

https://gms.tf/fosdem-2026.html

Published: October 11, 2026 16:00

After having sampled the FOSDEM 2026 talks, these are my top five recommendations. On challenges implementing White Rabbit time synchronisation and why most FPGA kits aren't sufficient: White Rabbit for the masses: distributed coherent SDR on generic…

Better Datamash Build Story with Meson

https://gms.tf/datamash-meson.html

Published: March 29, 2026 16:00

This article is a small case study on introducing the Meson build tool into a legacy Autotools and Gnulib centric code base, i.e. the GNU Datamash project. With Meson, the result builds twice as fast and configures one order of magnitude faster while only…

Injecting Code into a Linux Process

https://gms.tf/inject_code.html

Published: December 6, 2024 09:00

Say - entirely hypothetically - we know a shell script that is executed with root privileges via sudo and we found a way for normal users to convince it to call their own code. For demonstration purposes it then would be nice to have code that invokes a…

The curious case of nanosleep vs. hr_sleep

https://gms.tf/hr_sleep.html

Published: July 9, 2024 17:00

This weekend, I finally got around reading a bookmarked paper that proposes an improved nanosleep: Faltelli, Marco & Belocchi, Giacomo & Quaglia, Francesco & Pontarelli, Salvatore & Bianchi, Giuseppe. (2021). Metronome: adaptive and precise intermittent…

Blocking Audio Ads

https://gms.tf/blocking-audio-ads.html

Published: June 16, 2024 23:00

This article describes an approach to blocking ads in audio files and introduces software that implements it. Motivation¶ The modern web is unbearable without a good ad-blocker such as uBlock Origin. Unfortunately, the online marketing industry, while…

Shift Typing

https://gms.tf/shift-typing.html

Published: October 7, 2023 16:00

This article introduces shift-tutor, a Linux program that filters shift key events to improve or verify touch typing skills. Rationale¶ Most keyboards contain two shift keys, i.e. one located on the left bottom and the other on the opposite side: Source:…

Fosi Audio TDA7498E Amplifier Review

https://gms.tf/fosi-review.html

Published: December 31, 2022 19:00

Recently, I was in the market for a Class-D amplifier to replace an aging model. This article reviews the very compact Fosi Audio TSA7498E 2 channel amplifier I bought from a China based business, via Amazon. tl;dr: Can't recommend, use something better. …

Scanning I2C addresses

https://gms.tf/i2c-scanner.html

Published: September 21, 2022 14:00

I2C is a simple open-drain bus that is popular for connecting devices to microcontrollers (MCUs), such as sensors, RTCs, displays etc. Devices on the I2C bus are addressed by 7 bits and the bus data and clock lines are pulled-up by a set of pull-up…

Measuring PWM Signals with a Pokit Meter

https://gms.tf/pwm-fft.html

Published: July 3, 2022 13:00

This article describes how to measure a pulse-width-modulated (PWM) signal using the Pokit Meter device. The Pokit Meter is a very small digital multimeter (DMM) like device that can be interfaced over Bluetooth Low Energy (BLE). Due to its design and…

Getting started with the GD32VF103 RISC-V Microcontroller

https://gms.tf/riscv-gd32vf103.html

Published: May 8, 2022 12:00

The GD32VF103 is an inexpensive 32 bit RISC-V CPU that integrates a bunch of peripherals. In other words, it's a cheap RISC-V microcontroller (MCU). This article describes how to hook it up, to set up an development environment and do some first steps with…

On the Costs of Syscalls

https://gms.tf/on-the-costs-of-syscalls.html

Published: August 30, 2021 13:00

It's well known that syscalls are expensive. And that software mitigations against CPU bugs (such as Meltdown) even have made them more expensive. But how expensive are they really? To begin to answer this question I wrote a small micro-benchmark in order…

The Rise of Meson

https://gms.tf/the-rise-of-meson.html

Published: August 7, 2021 11:00

More and more open source projects seem to switch to the Meson build tool, in the last years. In an attempt to quantify this development I looked at the build tools usage by Fedora packages, during the last 14 years. About Meson¶ Meson is a build tool with…

Perfect Hashing

https://gms.tf/perfect-hashing.html

Published: November 22, 2020 15:00

The beauty of perfect hashing is that you never have to deal with any collisions during item lookup. I recently created libphashtable, a perfect hashing hash table library for C/C++ which focuses on minimizing item lookup latency jitter. This article…

Deploying Full Disk Encryption in the Cloud with Ansible

https://gms.tf/fedora-initramfs.html

Published: November 17, 2020 11:00

Deploying a new virtual machine 'in the cloud' is simple enough and fast. As long as one doesn't need to setup an encrypted root filesystem. This article shows how to automate the setup of a Fedora system with an encrypted root filesystem remotely - 'in…

Deploying SSH Host Keys with Digital Ocean Droplets

https://gms.tf/ssh-host-key-deployment.html

Published: June 5, 2020 20:00

When deploying a VM in a remote location one might end up in an impossible situation: a VM base image doesn't contain SSH host keys as otherwise the image couldn't be shared between multiple hosts. But if SSH host keys are auto-generated during the first…

Programming with RISC-V Vector Instructions

https://gms.tf/riscv-vector.html

Published: January 24, 2020 23:00

Perhaps the most interesting part of the open RISC-V instruction set architecture (ISA) is the vector extension (RISC-V "V"). In contrast to the average single-instruction multipe-data (SIMD) instruction set, RISC-V vector instructions are vector length…

Announcing MANPATH.be

https://gms.tf/announcing-manpathbe.html

Published: July 7, 2019 12:00

Recently, I launched MANPATH.be - a site for convenient man page browsing. It provides access to the man pages of different distributions, including Fedora, CentOS and OpenSolaris. The about page concisely describes some of the sites features, e.g. human…

The Anatomy of a Firefox Malware Addon

https://gms.tf/the-anatomy-of-a-firefox-malware-addon.html

Published: March 23, 2019 09:00

Some time ago, I was contacted to fix a computer running Ubuntu. Basically, after many flawless LTS distribution upgrade the last one failed and made the graphical boot hang hard. Thus, the fix was to backup the home directory, re-install a fresh Ubuntu…

Touch Typing

https://gms.tf/touch-typing.html

Published: December 15, 2018 17:00

Getting along without touch typing is possible. But learning touch typing is usually a big productivity boost, reduces stress and may prevent typical keyboard induced health risks. This article describes some learning approaches and optimization…

Configuring SPF to make Google happy

https://gms.tf/configuring-spf-to-make-google-happy.html

Published: May 10, 2018 10:00

Lately, Google mail servers are getting more extravagant in what mail they accept. Setting up a Sender Policy Framework (SPF) DNS record is a relatively low effort way to get mail though users of the Google mail service. (Those users aren't necessarily…

Work-related Movies

https://gms.tf/work-related-movies.html

Published: April 18, 2018 19:10

This article features a watch list of work related movies. A list for getting some peace of mind in the evening after working overtime. Each movie has some relation to a pathological work related setting. Not always on the surface, but more on a deeper…

Dtracing Passwords for Fun

https://gms.tf/dtracing-passwords-for-fun.html

Published: December 17, 2017 21:30

Going through an old hardware stash, I've noticed a harddisk that was part of a Solaris test system of mine I disassembled 10 years ago. The disk contains an interesting artifact I implemented at that time: a proof-of-concept for capturing user entered…

NFS VM Cached Read Illustrated

https://gms.tf/nfs-vm-cached-read-illustrated.html

Published: August 12, 2017 16:12

This article illustrates how the virtual memory (VM) subsystem of the Linux kernel is able to cache files that are located on an NFS server. Environment High-Level View Dstat NFS Traffic Closing Remarks Environment¶ In this small experiment we just…

Check CPU Microcode Version on Linux

https://gms.tf/check-cpu-microcode-version-on-linux.html

Published: July 1, 2017 08:10

Debian recently released a warning advisory regarding a hardware bug in the hyperthreading implementation on certain Skylake/Kaby Lake Intel CPUs. It can be mitigated by a microcode firmware update - at least on some models. This article is about checking…

Reasons for Rooting Android

https://gms.tf/reasons-for-rooting-android.html

Published: June 15, 2017 19:10

A stock Android device is locked down, by default. Rooting is the process of getting access to the root user (think: installing su). This article lists several advantages of a rooted device. NTPsync Create USB Mass Storage devices Simple Backups Separate…

Fedora as Grml replacement

https://gms.tf/fedora-as-grml-replacement.html

Published: March 12, 2017 20:00

Grml is a Linux Live CD distribution geared towards system administration tasks and other console work. Unfortunately, its development has slowed down in the past years, i.e. the latest stable release is from 2014. In 2017, when dealing with modern…

Updating Samsung SSD Firmware in the 21st Century

https://gms.tf/updating-samsung-ssd-firmware-in-the-21st-century.html

Published: February 17, 2017 20:10

The firmware updates for the Samsung 840 EVO SSDs come as ISO images which isn't very helpful if your system doesn't have a CDROM drive. It turns out that the ISO images just contain DOS binaries, though. This article describes how to use a FreeDOS USB…

Btrfs requires noatime

https://gms.tf/btrfs-requires-noatime.html

Published: February 8, 2017 20:10

Traditionally, UNIX filesystems also maintain the access time (atime) of a file. This is very much an anti-feature because it yields a write operation for each read operation. Which is obviously bad for performance. Since Btrfs is a copy-on-write (COW)…

Updating the BIOS on a Dell Latitude E7270

https://gms.tf/updating-the-bios-on-a-dell-latitude-e7270.html

Published: February 6, 2017 09:10

Dell distributes BIOS updates for the Latitude E7270 as PE32 Windows GUI executables. It turns out that the BIOS itself is able to extract the firmware images from such executables and to apply them. HOWTO¶ Get the latest BIOS update executable from e.g. …

When curl sends 100-continue

https://gms.tf/when-curl-sends-100-continue.html

Published: January 28, 2017 09:10

When sending a POST request with curl it sometimes automatically adds an Expect: 100-continue header. The following summarizes under which conditions curl/libcurl adds this header. Background¶ The Expect: 100-continue header is specified in HTTP 1.1 and…

Link Layer Discovery Protocol

https://gms.tf/link-layer-discovery-protocol.html

Published: December 14, 2016 09:10

The Link Layer Discovery Protocol (LLDP) probably isn't the most popular protocol but it can be useful for troubleshooting purposes and for mapping the neighbourhood of a host. Its purpose is basically to send/receive key/value pairs that are of general…

Counting CPU Events

https://gms.tf/counting-cpu-events.html

Published: October 16, 2016 08:10

This article discusses hardware performance counter measurements obtained for a character search benchmark running on Intel x86 and SPARC hardware. Those results help to explain the big runtime differences between a SPARC T5 system and Intel x86 ones…

SPARC and PPC find benchmark results

https://gms.tf/sparc-and-ppc-find-benchmark-results.html

Published: September 16, 2016 08:10

The article std::find() and memchr() Optimizations contains benchmark results for an Intel Core i5, an i7 and an older AMD system. This followup also adds results for a relatively recent SPARC system and an older PPC one. SPARC T5¶ First released in 2013,…

std::find() and memchr() Optimizations

https://gms.tf/stdfind-and-memchr-optimizations.html

Published: September 7, 2016 08:10

Assume you need to parse a record based format with flexible width and one-byte delimiters. When using C++, the std::find() STL algorithm is the obvious choice for efficiently locating the delimiters. The idiomatic C solution is to use memchr(). …

LD_LIBRARY_PATH considered harmful

https://gms.tf/ld_library_path-considered-harmful.html

Published: July 22, 2016 08:10

The purpose of the LD_LIBRARY_PATH environment variable is to instruct the linker to consider additional directories when searching for libraries. Its valid use case is the test of alternative library versions installed in non-standard locations. In…

Shipping Books (in Germany)

https://gms.tf/shipping-books-in-germany.html

Published: July 19, 2016 08:10

There are several products for shipping books in Germany. The 'Warensendung' product may be cheaper for certain books, but they are slowly transported and there is no tracking. The following table compares different attributes and constraints of the…

On sprintf() Fails

https://gms.tf/on-sprintf-fails.html

Published: July 15, 2016 22:00

The sprintf() and snprintf() C library functions are commonly used for formatting a string and writing the result into a buffer. But sometimes it is surprising in how many ways sprintf() can be misused. The Ugly The Pitfalls The Bad The Ugly¶ Some…