linux

630 Articles

iPhone 6 with Linux boot log on its screen

Boot Mainline Linux On Apple A7, A8 And A8X Devices

June 12, 2022 by 10 Comments

[Konrad Dybcio] tells about his journey booting Linux on A7/8/8X processors, playing around with an old iPhone 5 he’s got in a drawer. It’s been a two-year “revisit every now and then” journey, motivationally fueled by the things like Linux on M1 Macs announcement. In the end, what we have here is a way to boot mainline Linux on a few less-than-modern but still very usable iPhones, and a fun story about getting there.

[Konrad]’s work is based on the Sandcastle project research, but he couldn’t quite figure out how to make their code work, and had to make sense of it as he went. At some point, he got stuck on enabling the MMU, which was the main roadblock for a while. Joined by another developer intrigued by Apple hardware, they were hacking away at it, developing tools and neat tricks on their way, but to no avail. With the framebuffer accessible and no other decent debugging methods in sight, he tells about a code snippet they wrote that printed register values as valid barcodes Continue reading “Boot Mainline Linux On Apple A7, A8 And A8X Devices” →

A Linux Distribution For DOOM

June 9, 2022 by 40 Comments

If you’ve gone further into the Linux world than the standard desktop distributions like Ubuntu or Fedora, you have undoubtedly come across some more purpose-built distributions. Some examples are Kali for security testing, DragonOS for software-defined radio, or Hannah Montana Linux for certain music fans. Anyone can roll their own Linux distribution with the right tools, including [Shadly], who recently created one which only loads enough software to launch the 1993 classic DOOM.

The distribution is as simple as possible and loads no bloat other than what’s needed to launch the game. It loads the Linux kernel and the standard utilities via BusyBox, then runs fbDOOM, which is a port of the game specifically designed to run on the Linux framebuffer with minimal dependencies. After most of that, the only thing left is to use GRUB to boot the distribution, and in just a moment, Doomguy can start slaying demons. The entire distribution is placed into a bootable ISO file that can be placed on any bootable drive.

As far as DOOM hacks go, we’re used to seeing the game running on hardware it was never intended for like the NES  or on an office phone. This one, on the other hand, gives us a little more insight into just how little is needed for a full-fledged Linux distribution, as long as what you need to do is relatively straightforward.

Continue reading “A Linux Distribution For DOOM“ →

The SoM on an evaluation board, with two LEDs shining, one USB-C cable connected for power and another plugged into the OTG port

New Part Day: X1501 Makes For A Tiny And Open Linux SoM

June 5, 2022 by 26 Comments

Ever wanted to run Linux in an exceptionally small footprint? Then [Reimu NotMoe] from [SudoMaker] has something for you! She’s found an unbelievably small Linux-able chip in BGA, and designed a self-contained tiny SoM (System on Module) breakout with power management and castellated pads. This breakout contains everything you need to have Linux in a 16x16x2mm footprint. For the reference, a 16mm square is the size of the CPU on a Raspberry Pi.

This board isn’t just tiny, it’s also well-thought-out, helping you put the BGA-packaged Ingenic X1501 anywhere with minimal effort. With castellated pads, it’s easy to hand-solder this SoM for development and reflow for production. An onboard switching regulator works from 6V down to as low as 3V, making this a viable battery-powered Linux option. It can even give you up to 3.3V/1A for all your external devices.

The coolest part yet – the X1501 is surprisingly friendly and NDA-free. The datasheets are up for grabs, there are no “CONFIDENTIAL” watermarks – you get a proper 730-page PDF. Thanks to this openness, the X1501 can run mainline Linux with minimal changes, with most of the peripherals already supported. Plus, there’s Efuse-based Secure Boot if your software needs to be protected from cloning.

More after the break…

Continue reading “New Part Day: X1501 Makes For A Tiny And Open Linux SoM” →

Optimizing Linux Pipes

June 3, 2022 by 28 Comments

In CPU design, there is Ahmdal’s law. Simply put, it means that if some process is contributing to 10% of your execution, optimizing it can’t improve things by more than 10%. Common sense, really, but it illustrates the importance of knowing how fast or slow various parts of your system are. So how fast are Linux pipes? That’s a good question and one that [Mazzo] sets out to answer.

The inspiration was a highly-optimized fizzbuzz program that clocked in at over 36GB/s on his laptop. Is that a common speed? Nope. A simple program using pipes on the same machine turned in not quite 4 GB/s. What accounts for the difference?

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Linux Fu: Easy Widgets

June 2, 2022 by 5 Comments

Here’s a scenario. You have a microcontroller that reads a number of items — temperatures, pressures, whatever — and you want to have a display for your Linux desktop that sits on the panel and shows you the status. If you click on it, you get expanded status and can even issue some commands. Most desktops support the notion of widgets, but developing them is a real pain, right? And even if you develop one for KDE, what about the people using Gnome?

Turns out there is an easy answer and it was apparently inspired by, of all things, a tool from the Mac world. That tool was called BitBar (now XBar). That program places a widget on your menu bar that can display anything you want. You can write any kind of program you like — shell script, C, whatever. The output printed from the program controls what appears on the widget using a simple markup-like language.

That’s fine for the Mac, but what about Linux? If you use Gnome, there is a very similar project called Argos. It is largely compatible with XBar, although there are a few things that it adds that are specific to it. If you use KDE (like I do) then you’ll want Kargos, which is more or less a port of Argos and adds a few things of its own.

Good News, Bad News

The good news is that, in theory, you could write a script that would run under all three systems. The bad news is that each has its own differences and quirks. Obviously, too, if you use a complied program that could pose a problem on the Mac unless you recompile.

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Building Faster Rsync From Scratch In Go

June 1, 2022 by 53 Comments

For a quick file transfer between two computers, SCP is a fine program to use. For more complex, large, or regular backups, however, the go-to tool is rsync. It’s faster, more efficient, and usable in a wider range of circumstances. For all its perks, [Michael Stapelberg] felt that it had one major weakness: it is a tool written in C. [Michael] is philosophically opposed to programs written in C, so he set out to implement rsync from scratch in Go instead.

[Michael]’s path to deciding to tackle this project is a complicated one. His ISP upgraded his internet connection to 25 Gbit/s recently, which means that his custom router was the bottleneck in his network. To solve that problem he migrated his router to a PC with several 25 Gbit/s network cards. To take full advantage of the speed now theoretically available, he began using a tool called gokrazy, which turns applications written in Go into their own appliance. That means that instead of installing a full Linux distribution to handle specific tasks (like a router, for example), the only thing loaded on the computer is essentially the Linux kernel, the Go compiler and libraries, and then the Go application itself.

With a new router with hardware capable of supporting these fast speeds and only running software written in Go, the last step was finally to build rsync to support his tasks on his network. This meant that rsync itself needed to be built from scratch in Go. Once [Michael] completed this final task, he found that his implementation of rsync is actually much faster than the version built in C, thanks to the modernization found in the Go language and the fact that his router isn’t running all of the cruft associated with a standard Linux distribution.

For a software project of this scope, we find [Michael]’s step-by-step process worth taking note of for any problem any of us attempt to tackle. Not only that, refactoring a foundational tool like rsync is an involved task on its own, let alone its creation simply to increase network speeds beyond what most of us would already consider blazingly fast. We’re leaving out a ton of details on this build so we definitely recommend checking out his talk in the video below.

Thanks to [sarinkhan] for the tip!

Continue reading “Building Faster Rsync From Scratch In Go” →

Annotate PDFs On Linux With PDFrankenstein

May 28, 2022 by 20 Comments

On Windows and Mac machines, it’s not too troublesome to add text or drawings (such as signatures) to PDF files, but [Mansour Behabadi] found that on Linux machines, there didn’t seem to be a satisfying way or a simple tool. Being an enterprising hacker, [Mansour] set out to fill that gap, and the way it works under the hood is delightfully hacky, indeed.

The main thing standing in the way of creating such a tool is that the PDF format is a complex and twisty thing. Making a general-purpose PDF editing tool capable of inserting hyperlinks, notes, images, or drawings isn’t exactly a weekend project. But [Mansour] didn’t let that stop him; he leveraged the fact that tools already exist on Linux that can read and create PDF files, and tied them all together into what was at one point “a horrific patchwork of tools” which inspired the name pdfrankenstein.

The tool is a GUI that uses Inkscape and qpdf to convert a PDF page to an SVG file, set it as a locked background, then let the user add any annotations they desire, using Inkscape as the editor. After changes are made, the program removes the background, overlays the annotations back onto the originals, and exports a final file. Annotations can therefore be anything that can be done in Inkscape.

Curious about these and other tools for handling PDFs? We’ve shared some programs and tricks when we previously covered dealing with the PDF format in Linux.