linux

626 Articles

Linux Fu: A Warp Speed Prompt

March 20, 2025 by 26 Comments

If you spend a lot of time at the command line, you probably have either a very basic prompt or a complex, information-dense prompt. If you are in the former camp, or you just want to improve your shell prompt, have a look at Starship. It works on the most common shells on most operating systems, so you can use it everywhere you go, within reason. It has the advantage of being fast and you can also customize it all that you want.

What Does It Look Like?

It is hard to explain exactly what the Starship prompt looks like. First, you can customize it almost infinitely, so there’s that. Second, it adapts depending on where you are. So, for example, in a git-controlled directory, you get info about the git status unless you’ve turned that off. If you are in an ssh session, you’ll see different info than if you are logged in locally.

However, here’s a little animation from their site that will give you an idea of what you might expect: Continue reading “Linux Fu: A Warp Speed Prompt” →

Linux Fu: Use The Source (Command), Luke

March 13, 2025 by 12 Comments

You can argue if bash is a good programming language or not, but you can’t argue that it is a programming language. However, there are a few oddities about it that make it different from most other languages you probably know. For one thing, variables are dynamically scoped. Second, you can easily change variables in an upper scope. This leads to a problem when you want to do something like reset your path:

#!/bin/bash
#: This does NOT work
PATH=/usr/bin:/bin

Well, actually, it does work; it just doesn’t work the way you imagine it might. The key is to realize that when you execute our script (say, resetpath), a new copy of bash runs. It inherits all the variables from your shell. Now the script sets PATH for the new copy of bash. Anything else you run in that script will see your change. But when the script exits, the new copy of bash is gone and the old copy sees the same old PATH it always did.

Continue reading “Linux Fu: Use The Source (Command), Luke” →

Bits of GRUB syntax on pink background

Wake, Boot, Repeat: Remote OS Selection With GRUB And ESP

March 3, 2025 by 14 Comments

What do you do when you need to choose an OS at boot but aren’t physically near your machine? [Dakhnod]’s inventive solution is a mix of GRUB, Wake-on-LAN (WOL), and a lightweight ESP8266 running a simple HTTP server. In the past, [dakhnod] already enlightened us with another smart ESP hack. This one’s a clever combination of network booting and remote control that opens up possibilities beyond the usual dual-boot selector.

At its core, the hack modifies GRUB to fetch its boot configuration over HTTP. The ESP8266 (or any low-power device) serves up a config file defining which OS should launch. The trick lies in adding a custom script that tells GRUB to source an external config:

#!/usr/bin/env cat 
net_dhcp 
source (http,destination_ip_or_host:destination_port)/grub/config

Since GRUB itself makes the HTTP request, the system needs a running web server. That could be a Raspberry Pi, another machine, or the ESP itself. From there, a WOL-enabled ESP button can wake the PC and set the boot parameters remotely.

Is it secure? Well, that depends on your network. An open, unauthenticated web server dishing out GRUB configs is risky, but within a controlled LAN or a VLAN-segmented environment, it’s an intriguing option. Automation possibilities are everywhere — imagine remotely booting test rigs, toggling between OS environments for debugging, or even setting up kiosk machines that reconfigure themselves based on external triggers.

For those looking to take it further, using configfile instead of source allows for more dynamic menu entries, although it won’t persist environment variables. You could even combine it with this RasPi hack to control the uptime of the HTTP server. The balance between convenience and security is yours to strike.

If you’ve got your own wild GRUB customisation, let’s hear it!

Linux Fu: USB Everywhere

February 27, 2025 by 20 Comments

It is a common problem: I have a USB device on a computer out in the shop, and I want to use it from the comfort of my office. What to do? Well, you could remote desktop into the distant machine. But, honestly, I always find any remote desktop more than ssh clunky and somewhat undesirable. Fortunately, Linux can do virtually anything if you only know how to do it. So, this time, I’ll show you how to transport a USB device over your network. Of course, I have a network that reaches out to the shop. It should be a simple matter to tell my desktop machine that one of its USB devices lives across the network. Well, it wasn’t that simple, but it is doable.

The Tools

The whole thing involves a program called usbip. That should be the end of it, but of course, it isn’t. In order for this to work, both machines on the network will need some kernel modules and a daemon on the server: the machine with the USB devices to share.

You may be able to install usbip from your package manager. On Ubuntu, it is in the linux-tools-common package, so a simple apt-get might give you everything you need. I wasn’t so lucky. Continue reading “Linux Fu: USB Everywhere” →

Give Your Animal Crossing Villagers The Gift Of Linux

February 18, 2025 by 11 Comments

If you’ve played any of the versions of Nintendo’s Animal Crossing over the years, you’ll know that eventually you get to the point where you’ve maxed out your virtual house and filled it with all the furniture you could possibly want — which is arguably as close to “winning” the game as you can get.

But now thanks to the work of [decrazyo] there’s a piece of furniture that you can add to your Animal Crossing house that will never get old: an x86 emulator that boots Linux. As explained in the video below, this trick leverages the fact that Nintendo had already built a highly accurate Nintendo Entertainment System (NES) emulator into Animal Crossing on the GameCube, which could be used to run a handful of classic games from within the player’s virtual living room. But it turns out that you can get that emulator to load a user-provided ROM from the GameCube’s memory card, which opens the doors to all sorts of mischief.

Continue reading “Give Your Animal Crossing Villagers The Gift Of Linux” →

Screenshot of Linux in a PDF in a browser

Nice PDF, But Can It Run Linux? Yikes!

February 10, 2025 by 21 Comments

The days that PDFs were the granny-proof Swiss Army knives of document sharing are definitely over, according to [vk6]. He has managed to pull off the ultimate mind-bender: running Linux inside a PDF file. Yep, you read that right. A full Linux distro chugging along in a virtual machine all encapsulated within a document. Just when you thought running DOOM was the epitome of it. You can even try it out in your own browser, right here. Mind-boggling, or downright Pandora’s box?

Let’s unpack how this black magic works. The humble PDF file format supports JavaScript – with a limited standard library, mind you. By leveraging this, [vk6] managed to compile a RISC-V emulator (TinyEMU) into JavaScript using an old version of Emscripten targeting asm.js instead of WebAssembly. The emulator, embedded within the PDF, interfaces with virtual input through a keyboard and text box.

The graphical output is ingeniously rendered as ASCII characters – each line displayed in a separate text field. It’s a wild solution but works astonishingly well for something so unconventional.

Security-wise, this definitely raises eyebrows. PDFs have long been vectors for malware, but this pushes things further: PDFs with computational power. We know not to trust Word documents, whether they just capable of running Doom, or trash your entire system in a blink. This PDF anomaly unfolds a complete, powerful operating system in front of your very eyes. Should we think lightly, and hope it’ll lead to smarter, more interactive PDFs – or will it bring us innocent looking files weaponized for chaos?

Curious minds, go take a look for yourself. The project’s code is available on GitHub.

Continue reading “Nice PDF, But Can It Run Linux? Yikes!” →

UScope: A New Linux Debugger And Not A GDB Shell, Apparently

February 7, 2025 by 7 Comments

[Jim Colabro] is a little underwhelmed with the experience of low-level debugging of Linux applications using traditional debuggers such as GDB and LLDB. These programs have been around for a long time, developing alongside Linux and other UNIX-like OSs, and are still solidly in the CLI domain.  Fed up with the lack of data structure support and these tools’ staleness and user experience, [Jim] has created UScope, a new debugger written from scratch with no code from the existing projects.

GBD, in particular, has quite a steep learning curve once you dig into its more advanced features. Many people side-step this learning curve by running GDB within Visual Studio or some other modern IDE, but it is still the same old debugger core at the end of the day. [Jim] gripes that existing debuggers don’t support modern data structures commonly used and have poor customizability. It would be nice, for example, to write a little code, and have the debugger render a data structure graphically to aid visualisation of a problem being investigated. We know that GDB at least can be customised with Python to create application-specific pretty printers, but perhaps [Jim] has bigger plans?

Continue reading “UScope: A New Linux Debugger And Not A GDB Shell, Apparently” →