Joachim Wiberg troglobit

Ubuntu Server Setup - with netplan

Introduction

The assumption here is that you're now starting with a Ubuntu 22.04 LTS Server or newer, rather than Desktop, base (Ubuntu Desktop deploys NetworkManager rather than systemd-networkd by default). This box has an AMD Ryzen CPU.

The goal is networking configured for static addressing using systemd-networkd and netplan. Note that punctuation (including hypens, '-') and indentation are significant when working with netplan YAML files.

There are a lot good arguments against using netplan. I have tried NetworkManager (packages named "network-manager", but the service is "NetworkManager.service" -- go figure) on Ubuntu Server, and was

Testing GFM

Heading 1

Starting test 0005-operational_all █ 
2024-10-10 22:42:17 # Starting (2024-10-10 22:42:17)
2024-10-10 22:42:17 # host:    monza
2024-10-10 22:42:17 #     tgt:     swp1
2024-10-10 22:42:17 # target:  alder1
2024-10-10 22:42:17 # mgmt: x10

CFLAGS="-Wall -Werror -Wextra -Wno-unused-parameter -Wformat=2 -Wformat-overflow=2 -Winit-self -Wstrict-overflow=4 -Wno-format-truncation -Wno-format-nonliteral -Wimplicit-function-declaration"

Blinking LEDs in Linux

First check you have the timer trigger loaded:

root@gimli:~# lsmod |grep led
snd_ctl_led            24576  0
input_leds             16384  0
snd                   135168  45 snd_ctl_led,snd_hda_codec_generic,snd_seq,snd_seq_device,snd_hda_codec_hdmi,snd_hwdep,snd_hda_intel,snd_usb_audio,snd_usbmidi_lib,snd_hda_codec,snd_hda_codec_realtek,snd_sof,snd_timer,snd_compress,thinkpad_acpi,snd_soc_core,snd_pcm,snd_rawmidi
soundcore              16384  2 snd_ctl_led,snd

Debug a script callback to console

exec >/dev/console 2>&1
set -x

Ignore error on a particular line in `set -e`

possibly-failing-command ||:

Redirect STDERR to STDOUT

HowTo Insert Unicode Characters in Emacs

The magic keybinding is

C-x 8 RET
Insert character (Unicode name or hex): 2015
―

https://charbase.com/2015-unicode-horizontal-bar

HowTo: using mping for (fun and) profit

Ever since I started working with multicast back in the early 2000's, I've had to make my own tools. There weren't that many useful ones available, at least not in the Open Source space where I worked.

The first tool made, mcjoin, was based on an example an IBM'er had made public. I used that, the standard ping(1) tool, and tcpdump(1), to check my multicast flows.

Developing & debugging libnl

When I started out learning about libnl, around 10 years ago, I did not fully understand it. Mostly because I didn't (want to) understand Netlink. A great way to learn something is to try to fix a bug, or develop a new feature, because then you will want to write both tests and demo applications, which you may end up having to debug! Debuggers give you backtraces, which will help you understand how your program works.

Note: for debugging embedded systems using gdb-server, see the following blog post I wrote

	#!/usr/bin/env python3

	import socket
	import time
	import threading

	class SsdpClient(threading.Thread):
	""" Simple SSDP client probe """
	SEARCH_INTERVAL = 5
	BCAST_IP = '239.255.255.250'