PrawnOS

A build system for making blobless Debian and mainline Linux kernel for the Asus c201 Chromebook with support for dmcrypt/LUKS root partition encryption

Build Debian filesystem with:

• No blobs, anywhere.
• Sources from only main, not contrib or non-free which keeps Debian libre.
• Currently PrawnOS supports xfce and lxqt as choices for desktop enviroment.
• full root filesystem encryption

Build a deblobbed mainline kernel with:

• Patches for reliable USB.
• Patches to support the custom GPT partition table required to boot.
• Support for Atheros AR9271 and AR7010 WiFi dongles.
• Support for CSR8510 (and possibly other) bluetooth dongles.

Don't want to use one of the two USB ports for the WiFi dongle? check out this

Why

Combined with Libreboot, an AR9271 or AR7010 WiFi dongle, and a libre OS (like Debian with the main repos, the one built by PrawnOS) the Asus c201 is a fully libre machine with no blobs, or microcode, or Intel Management Engine.

WARNING: flashing libreboot to asus c201 chromebooks that have recently been updated to a new version of chromeOS may leave the device in a non-functional (bricked) state.

If you do not have a way to recover your device by using an external flasher as described in the second part of this page https://libreboot.org/docs/install/c201.html it would be safest to wait until this issue is resolved. I have opened a bug with libreboot, which can be found here https://notabug.org/libreboot/libreboot/issues/666 If you have any information that may help with debugging, please post it there.

The install process of PrawnOS does not flash your bios, so it is safe to use along with the default coreboot/depthcharge and does not risk bricking your device

What is a blob?

In the world of free and open-source software, the term is used to refer to proprietary device drivers, which are distributed without their source code, exclusively through binary code; in such use, the term binary blob is common. wikipedia

Image Download

If you don't want to or can't build the image, you can find downloads under https://github.com/SolidHal/PrawnOS/releases

Dependencies

Building PrawnOS has been tested on Debian 10 Buster (in a VM).

NOTE: stretch doesn't work as the version of gcc-arm-none-eabi is too old!

Debian/Buster is the only build enviroment that is supported. These packages are required:

        apt install --no-install-recommends --no-install-suggests \
        bc binfmt-support bison build-essential bzip2 ca-certificates cgpt cmake cpio debhelper \
        debootstrap device-tree-compiler devscripts file flex g++ gawk gcc gcc-arm-none-eabi git gpg \
        gpg-agent kmod libc-dev libncurses-dev libssl-dev lzip make parted patch \
        qemu-user-static sudo texinfo u-boot-tools udev vboot-kernel-utils wget

Build

Clone this Git repo: git clone --recurse-submodules https://github.com/SolidHal/PrawnOS

Build the PrawnOS-*-.img by running sudo make image

This has only been tested on a Debian Buster VM, and borrows some components from the host system to setup apt/debootstrap during the build process so I would recommend using a Debian Buster VM to avoid any issues.

Write to a flash drive or SD card

Write the 2GB image to a flash drive. Make sure to replace $USB_DEVICE with the desired target flash drive or SD card device. If you're not familiar with dd, check out Debian's how to page https://www.debian.org/CD/faq/#write-usb

sudo dd if=PrawnOS-*.img of=/dev/$USB_DEVICE bs=50M status=progress; sync

Installing

There are two ways to use PrawnOS.

The first and recommended option is to install it on a device other than the one you wrote the PrawnOS image to. click here

• This lets you install PrawnOS to the internal emmc, an SD card or a USB device
• This allows you to setup root encryption
• Installing to an external device allows you to try PrawnOS without removing Chrome OS or whatever Linux you are running on your internal storage (emmc), but USB drives especially are a much slower experience as the c201 only has USB 2.0.
• The internal emmc is much faster than a usb device or sd card for both reads and writes, data from some tests is available in #133
• If you want to boot from external media, I would suggest using an SD card.

The second option is to boot from the external USB or SD device you wrote the image to, and expand the image to take up the entire device. click here

• Expanding the PrawnOS image allows you to boot PrawnOS from the same USB or SD device that you wrote the image to
• Expansion does NOT support root encryption. For root encryption the filesystem must be written after the encrypted root is created.

Install to internal drive (emmc) or to SD card or USB drive

Now on the C201, insert the drive you wrote the PrawnOS image to. Press control+u at boot to boot from the external drive.

If you are running stock coreboot and haven't flashed Libreboot, you will first have to enable developer mode and enable USB / external device booting. A quick search should get you some good guides, but if you're having issues feel free to open an issue here on github.

At the prompt, login as root. The password is blank.

Now insert the other USB device or SD card you would like to install PrawnOS on. If you want to boot from the internal emmc, you have nothing to insert! Note: If you are installing to an external device, the filesystem portion may take a loooong time (20 minutes). This is because we are reading from one external device (the boot device) and writing to another external device. This more than saturates the USB and/or SD bus.

WARNING! THIS WILL ERASE YOUR INTERNAL EMMC STORAGE (your Chrome OS install or other Linux install and all of the associated user data) OR WHATEVER EXTERNAL DEVICE YOU CHOOSE AS YOUR INSTALL TARGET. Make sure to back up any data you would like to keep before running this.

Run:

cd /
./InstallPrawnOS.sh

Choose Install and follow the prompts. This will ask what device you want to install to and setup root encryption with a custom initramfs and dmcrypt/LUKS if you want. If you are curious how the initramfs, and root partition encryption work on PrawnOS check out the Initramfs and Encryption section in DOCUMENTATION.md If you run in to any problems please open an issue. If you install to the internal emmc this will show a bunch of scary red warnings that are a result of the emmc (internal storage) having a few unwritable (bad) blocks at the beginning of the device and the kernel message level being set low for debugging. They don't effect anything long-term. All C201s have these bad blocks at the beginning of the emmc

After the partitioning and the filesystem copy is complete, it will prompt you to install either the xfce4 or the lxqt desktop environment, sound, trackpad, and Xorg configurations It will also prompt you to make a new user that automatically gets sudo privileges.

After reboot, remove the external media you had booted from originally. If you installed to the internal emmc press control+d, if you installed to an external device press control+u

If you press nothing, it will boot to the internal storage by default.

Congratulations! Your computer is now a Prawn! https://sprorgnsm.bandcamp.com/track/the-prawn-song

Expand PrawnOS

Now on the C201, insert the drive you wrote the PrawnOS image to. Press control+u at boot to boot from the external drive.

If you are running stock coreboot and haven't flashed Libreboot, you will first have to enable developer mode and enable USB / external device booting. A quick search should get you some good guides, but if you're having issues feel free to open an issue here on github.

At the prompt, login as root. The password is blank. Run:

cd /
./InstallPrawnOS.sh

Choose Expand at the prompt

If you run in to any problems please open an issue.

Now you can choose to install the packages, which are either the xfce4 or the lxqt desktop enviroment, sound, trackpad, and Xorg configurations. It will also prompt you to make a new user that automatically gets sudo privileges.

If you choose in install the packages, when installation is complete it will reboot. Press control+u at boot once again, and you'll get to a login screen.

Congratulations! Your computer is now a Prawn! https://sprorgnsm.bandcamp.com/track/the-prawn-song

If you simply want a basic Linux environment with no desktop environment or window manager:

Say no at the prompt to install packages and a desktop environment. Congratulations: you are done! Welcome to PrawnOS. You should probably change the root password and make a user, but I'm not your boss or anything so I'll leave that to you.

Connecting to WiFi in a basic environment

If have a basic environment without xfce or lxqt you can connect to WiFi using wpa_supplicant by running the following commands:

wpa_passphrase <Network_name> <network_password> > wpa.conf
wpa_supplicant -i wlan0 -c wpa.conf

Now switch to another tty by pressing ctrl+alt+f2 Login as root, and run

dhclient wlan0

When that finishes, you should have access to the internet.

Upgrading the kernel

The script UpgradeKernel.sh located in /InstallResources can be ran be used to copy the kernel, modules, initramfs, and ath9k firmware from a newer version of PrawnOS running on a USB drive or SD card onto an older version of PrawnOS installed on the laptops internal emmc storage.

To use it, write the new PrawnOS image to a USB drive or SD card, boot the laptop to it by pressing control+u at boot, navigate to the /InstallResources folder, and run the script.

Documentation

Some useful things can be found in DOCUMENTATION.md

Make options, developer tools

(All of these should be run as root or with sudo to avoid issues) The makefile automates many processes that make debugging the kernel or the filesystem easier. To begin with:

make kernel_config cross compiles make menuconfig Cross compiling is required for any of the Linux kernel make options that edit the kernel config, as the Linux kernel build system makes assumptions that change depending on what platform it is targeting.

make kernel builds just the kernel

make filesystem builds the -BASE filesystem image with no kernel

make initramfs builds the PrawnOS-initramfs.cpio.gz, which can be found in /build

make image builds the initramfs image, builds the kernel, builds the filesystem if a -BASE image doesn't exist, and combines the two into a new PrawnOS.img using kernel_inject

make kernel_inject Injects a newly built kernel into a previously built PrawnOS.img located in the root of the checkout. Usually, this will be a copy of the -BASE image made by make filesystem. Only use this if you already have a built kernel and filesystem -BASE image.

You can use the environment variable PRAWNOS_SUITE to use a Debian suite other than Buster. For example, to use Debian stretch, you can build with sudo PRAWNOS_SUITE=stretch make image. Note that only stretch and buster have been tested.

You can use the environment variable PRAWNOS_DEBOOTSTRAP_MIRROR to use a non-default Debian mirror with debootstrap. For example, to use Debian's Tor onion service mirror with debootstrap, you can build with sudo PRAWNOS_DEBOOTSTRAP_MIRROR=http://vwakviie2ienjx6t.onion/debian make image.

Crossystem / mosys

crossystem is installed from the debian repos and mosys (a dependency of crossystem, and all around useful tool) is built and installed as part of the PrawnOS filesystem build.

Warning: running these commands can leave you in a state where you cannot boot.

Specifically, enabling dev_boot_signed_only will prevent PrawnOS from booting, as no key is stored in the bootloader for the PrawnOS Linux kernel Its also a bad idea to disable dev_boot_usb unless you are positive you will always be able to boot to the internal emmc. Unless you are running libreboot, the only way to recover if you get in one of these states is to reinstall chromeos using recovery media

Example crossystem and mosys commands, most require root privileges

Kernels signature verification:

sudo crossystem dev_boot_signed_only=1 enable sudo crossystem dev_boot_signed_only=0 disable

External media boot:

sudo crossystem dev_boot_usb=1 enable sudo crossystem dev_boot_usb=0 disable

Legacy payload boot:

sudo crossystem dev_boot_legacy=1 enable sudo crossystem dev_boot_legacy=0 disable

Default boot medium: sudo crossystem dev_default_boot=disk internal storage sudo crossystem dev_default_boot=usb external media sudo crossystem dev_default_boot=legacy legacy payload

Dump system state: sudo crossystem

View mosys command tree: sudo mosys -t

On older PrawnOS releases or other distributions, you can run the buildCrossystem.sh script located in scripts/InstallScripts/ to build and install mosys and install crossystem

sudo /InstallScripts/buildCrossystem.sh

GPU Support

Watch this link for GPU support: https://gitlab.freedesktop.org/panfrost and this one for progress updates: https://rosenzweig.io/blog/gpu-feed.xml

Build the WiFi dongle into the laptop

Sick of having a USB dongle on the outside of your machine for wi-fi? Want to be able to use two USB devices at once without a hub? Check out the instructions here: https://github.com/SolidHal/AsusC201-usb-wifi-from-webcam Warning: decent soldering skills required

Troubleshooting

The pulse audio mixer will only run if you are logged in as a non-root account. This is an issue (feature?) of pulse audio

Credits and Legal Information

Thanks to dimkr for his great devsus scripts for the Chrome OS 3.14 kernel, from which PrawnOS took much inspiration https://github.com/dimkr/devsus

Because PrawnOS started as a fork of devsus-3.14, some of this repo's ancient history can be found at https://github.com/SolidHal/devsus/tree/hybrid_debian

PrawnOS is free and unencumbered software released under the terms of the GNU General Public License, version 2; see COPYING for the license text. For a list of its authors and contributors, see AUTHORS.