troglobit

The UNIX utility dd is actually inherited from VMS, hence the opt=arg instead of --opt=arg syntax.

Here we write the input file (if) to the output file (of), using a larger block size (bs) than default (512 bytes). We'd like to see the progress of the write, this is not the default, and we want to avoid caching in the Linux VFS, so we set output flag (oflag) to direct, i.e. write-through.

sudo dd if=linuxmint-20-cinnamon-64bit.iso of=/dev/sdb bs=1M status=progress oflag=direct

Watch out, check the output file (/dev/sdb) matches your USB stick, otherwise you'll kill all the kittens!

troglobit

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

troglobit

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

troglobit

-- @author Peter J. Kranz (Absurd-Mind, peter@myref.net)
-- Any questions, criticism or praise just drop me an email

local awful = require("awful")

local M = {}

-- get the current Pid of awesome
local function getCurrentPid()
    -- get awesome pid from pgrep

troglobit

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

troglobit

grep Vm /proc/$(ps aux | grep inadyn |head -1 |awk '{print $2}')/status

troglobit

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.

troglobit

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

troglobit

#BR2_ROOTFS_OVERLAY := $(BR2_ROOTFS_OVERLAY) $(BR2_EXTERNAL_NETBOX_PATH)/jocke

LINUX_OVERRIDE_SRCDIR = /home/jocke/src/linux
#IPROUTE2_OVERRIDE_SRCDIR = /home/jocke/src/iproute2
#MDIO_TOOLS_OVERRIDE_SRCDIR = /home/jocke/src/github.com/jocke/mdio-tools
#MDIO_TOOLS_AUTORECONF = YES
#PLY_OVERRIDE_SRCDIR = /home/jocke/src/github.com/jocke/ply
#PLY_AUTORECONF = YES
#TCPDUMP_OVERRIDE_SRCDIR = /home/jocke/src/github.com/the-tcpdump-group/tcpdump
#LIBPCAP_OVERRIDE_SRCDIR = /home/jocke/src/github.com/the-tcpdump-group/libpcap

troglobit

ANSI Escape Sequences

Standard escape codes are prefixed with Escape:

• Ctrl-Key: ^[
• Octal: \033
• Unicode: \u001b
• Hexadecimal: \x1B
• Decimal: 27