Stephen Holdaway stecman

SSH key-based sudo authentication

To run privileged tasks without resorting to passwordless-sudo (NOPASSWD), you can use the libpam ssh_agent_auth module to authenticate based on SSH public keys in a separate authorized keys file.

This module requires SSH connections to be made with the -A command line option, or the ForwardAgent yes config option. You also need a local SSH agent running with the required key added.

I've presented this as an Ansible playbook + variables as it's a useful application

Screen recording in Sway (and other Wayland compositors)

Some notes on screen recording in Wayland / Sway on Ubuntu as I had issues getting a good result. This was using a machine with Intel Arc graphics.

Setup

Install wf-recorder:

sudo apt-get install wf-recorder

MicroPython motor control on Raspberry Pi Pico

Getting started

See getting started with Raspberry Pi Pico. This walks you through installing Thonny, an editor that supports interacting with MicroPython running on the Pico. The board already has MicroPython installed on it, so you can skip that step.

Basics of embedding files in firmware

This is an appendix item for Unicode Input Terminal.

With gcc, the linker can can happily create an object file from arbitrary input files. This is useful for embedding images, fonts, etc into firmware. Full CMake code at the end, but the important parts are:

# Create object file

Bake glyphs from fonts to image files (Python)

This is an appendix item for Unicode Input Terminal.

Protoype code to pre-render 240x240 screens, each with a glyph and codepoint metadata.

# Download Unicode metadata
wget https://unicode.org/Public/UNIDATA/UnicodeData.txt
wget https://unicode.org/Public/UNIDATA/Blocks.txt

Bake glyphs from fonts to image files (Rust)

This is an appendix item for Unicode Input Terminal.

Find all of the Unicode codepoints a font can represent and renders them to invidiaul image files. Note the output directory is hard-coded to /tmp/rendered.

cargo run <font-file, ...>

Writing to LTO tape with a text index and a memory buffer

This script is for writing to LTO tape on Linux with tar and producing a plain text index file. It uses a large memory buffer to keep the destination tape drive fed when the source drive can't consistently match the tape's write speed (eg. when there are a mix of small and large files).

This was written for a small, manually managed tape collection. It writes tape index information and tar listings as text to a file. This file can be stored separately, searched easily, and appended to the end of the tape if you want your tapes to be self-describing:

Automatic speaker power control from multiple audio sources

Switches mains power on for speakers while an audio signal is detected, and times out after a period of silence. Uses the AVR ATTiny13a and a couple of op-amps.

Mains switching is achieved by emulating a MS-6147-RC 433.92 MHz remote control with firmware and a simple simple on-off-keying (OOK) transmit module.

This solves two problems for me:

	# Move workspace left and right (swap if conflicting)
	bindsym $mod+Ctrl+Shift+Left exec $HOME/.i3/i3-swap.py left
	bindsym $mod+Ctrl+Shift+Right exec $HOME/.i3/i3-swap.py right

	# Make the next free workspace number, whatever that is
	bindsym $mod+Ctrl+Return exec $HOME/.i3/i3-makews.py

	# Rotate focus through visible workspaces on different monitors
	bindsym $mod+x exec $HOME/.i3/i3-nextoutput.py

	#!/bin/bash

	# Hide the decorations of a window.
	# Defaults to hiding the focused window's decorations.
	# Pass -m to use the mouse to select the target window.

	# Get the focused window's ID
	ID_OPTION="-id $(xdotool getwindowfocus)"

	while getopts 'm' flag; do