Linux is now running inside a PDF because people are amazing

Just weeks after getting 1993’s Doom running inside a PDF file, ‘ading2210’ has returned by getting an operating system to run inside one. In a new video, the high school programmer has managed to get Linux running, with a demonstration of the terminal and plenty of security warning messages.

It’s obviously not a viable option to run in the day-to-day, but ading2210’s pushing of the PDF is nothing short of fascinating. On his GitHub, he elaborates how he managed to get the software working, which includes leveraging often overlooked features of the PDF file format.

PDFs aren’t just static images and text but can involve video and some interactivity. As Ading points out, PDFs can also harness the power of Javascript, which can then be leveraged to run much more advanced things, like Linux or Doom.

The student points out that “C code can be compiled to run within a PDF”, the basis of Linux. Ading then has it target a compiled “modified version of the TinyEMU RISC-V emulator”, which replaces the original file the PDF would look for.

This creates a virtual machine, which can then be used as you would typically use a Linux terminal. It’s not fully featured and is very slow, but it’s utterly fascinating to poke at.

Effectively, the PDF file is emulating Linux through an emulation of the RISC-V architecture. RISC-V has been around for years but is quickly coming into its own recently, with more projects utilizing it. It’s meant to be an open-source alternative to processor architectures like x86 and ARM, which are used by Intel, AMD, and Qualcomm.

Products like the Raspberry Pi Pico 2 microcontroller have launched with a RISC-V chip onboard for additional processing.

The projects are available for anyone to tinker around with and even use, but you’ll need to use a Chromium-based browser. This includes browsers like Chrome, Brave, and Arc. In Firefox, both the Linux and Doom PDF files display visual errors.

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