dragora-c201

Installing Dragora 3 on the Asus Chromebook C201

This repo is a guide on how to install Dragora version 3 on the C201 Chromebook. Some of the things require some GNU/Linux know-how but I will attempt to make it easy to understand. This will not only help you install Dragora but should also help you boot your own modified version of Linux/Linux-libre or any ARMv7l-supported GNU/Linux distributions on the C201.

Recommendations

Before I start, there are some recommendations I would like to give. I highly recommend removing the original BIOS, coreboot, with the fully-free libreboot. This will not only make the system more free but it will actually boot slightly fast this way. Plus it removes the ChromeOS nonsense at startup. This is not a guide for libreboot; that is found here. I also recommend using Linux-libre instead of Linux because Linux contains nonfree software blobs. That being said, this guide will work with Linux but I will be using Linux-libre. If you do decide to use Linux-libre make sure to get a USB wireless dongle. There is no support for the internal wireless card. I highly recommend the ath9k wireless card beause they are fully free. They can be found on ThinkPenguin.

I also recommend that you install your system on an external source (at least 8GB is good). Just in case things go wrong, you can still use ChromeOS to fix the issues. Once you've gotten a working external system, you can then install onto the internal eMMC at your own risk for it hasn't been tested yet.

Prerequisites

If you installed libreboot on your system, you can skip all prerequisites!

Before you can boot anything, you must do some stuff on ChromeOS. First and foremost, you are going to want an external media. I used a thumb drive in this guide but you may use an SD card. It is recommended that you use an 8GB one because this guide assumes you are using one. You should also make sure that you have the newest version of ChromeOS on your system but you probably already do.

Enabling Developer Mode

In order to have access to a shell on ChromeOS, you will need to enable developer mode. You will also need developer mode to enable external booting and to disable signed kernel verification.

To enable developer mode:

• Hold down the ESC and refresh (the circular arrow) keys then power on the device.
  • The device will reboot and display a recovery mode screen.
• Press ctrl + d to make the system boot into recovery
• Switching to recovery mode will delete any content/data stored on your device
• Confirm. This can take 10+ minutes. Be patient.

Enable External Booting

There are technically 2 different ways to enable this feature, however, I will only show 1 of these ways because it doesn't require any additional software. You can see the other way here.

• Boot up the system and login to ChromeOS as guest.
• Open the Chrome browser and press ctrl + alt + t.
  • This will open crosh a terminal-like prompt for the Chrome browser.
• Type shell and press enter.
  • You are now in a GNU/Linux shell.
• You must now login as root, to do this, type sudo -s and hit enter.
  • If you are prompted for a password, follow these steps to reset the device. This should fix that issue.
• Now type crossystem dev_boot_usb=1 and press enter.
  • You have enabled external booting

NOTE: When you reboot the machine, you can press ctrl + u to boot off an external device and ctrl + d to boot off the internal eMMC. If you wait 30 seconds (or 3 seconds on libreboot) it will boot off the eMMC.

Installing Dragora ARM onto an External Media

NOTE: From this point on, things may be different if you wish to install a different GNU/Linux distribution.

Plug in the media you wish to install Dragora on in the device. You must now partition the media with 2 partitions: kernel and root. However, we must use GPT for our partitioning scheme. Make sure that you change the device (/dev/sdX or /dev/mmcblk1X) to the appropriate value. I used a thumb drive and my media was under the name /dev/sda. If you use an SD card, you will have something like /dev/mmcblk1.

• Start by creating a new GPT table like so: # fdisk /dev/sda

  • Then type g and press enter. This will create a new GPT table on the media.
  • Now type w and press enter to write the data to the media.

• Obtain cgpt either from your package manager or steal it from ChromeOS like so:

  # mount -o ro /dev/mmcblk0p3 /mnt
  # cp /mnt/usr/bin/cgpt /usr/bin
  # umount /mnt
  

• Now we can create the GPT scheme with:

  # cgpt create /dev/sda
  

• Create a kernel partition with:

  # cgpt add -i 1 -t kernel -b 8192 -s 32768 -l Kernel -S 1 -T 5 -P 10 /dev/sda
  

• Run the command

  # cgpt show /dev/sda
  

  • It will print out something like this: ``` localhost / # cgpt show /dev/sda start size part contents 0 1 PMBR 1 1 Pri GPT header 8192 32768 1 Label: "Kernel" Type: ChromeOS kernel UUID: E3DA8325-83E1-2C43-BA9D-8B29EFFA5BC4 Attr: priority=10 tries=5 successful=1
    

  15633375 32 Sec GPT table 15633407 1 Sec GPT header

  * Take the *start number* from the GPT table sector (in this example, it's
  15633375) and subtract 40960 from it. In my case, that's 15592415. Take that
  number and replace it where the "xxxxxx" is in this command:
  

  cgpt add -i 2 -t data -b 40960 -s xxxxxx -l Root /dev/sda

  This will create a root partition that will fill up the rest of the device.
  * NOTE: I have yet to test have multiple partitions such as /tmp, /boot, etc.
  * Now that you have both partitions made it's time to populate them. Format your
  second partition to ext4:
  

  # mkfs.ext4 /dev/sda2 ```

• Extract the rootfs tarball onto our external media. Let us go somewhere safe:

  # cd /tmp
  

  • While here create a new directory to mount our media:

    # mkdir root
    

  • Download the tarball:

    # wget http://dragora.org/dragora3/armv7-a/dragora-armv7-a-3.0.0-rootfs.tar.lz
    

  • Alternatively, you can build the system from scratch using the armv7-a architecture with qi: http://dragora.org/repo.fsl/artifact/01db86c75037bc24

  • Mount your media to the temporary directory:

    # mount /dev/sda2 root
    

  • Finally, unpack the tarball into the temporary directory:

    # tar -xf dragora-armv7-a-3.0.0-rootfs.tar.lz -C root
    

• You have a very minimal version of Dragora 3 installed to the media now.

(Untested) Flashing the Kernel (using Devsus)

The easiest way to use a deblobbed version of the ChromeOS kernel is to follow the instructions for building Devsus (https://github.com/dimkr/devsus/). Install that sucker onto a thumb drive and steal that kernel from there like so:

• Boot into the Devsus system.

• Run the following command to flash the kernel to the kernel partition:

  # dd if=root/boot/vmlinux.kpart of=/dev/sda1
  

• NOTE: Remember to change /dev/sda1 to the appropriate value for your device!

• Unmount the device:

  # umount root
  

• Sync the system for good measure:

  # sync
  

At this point you should have a working Dragora 3 install. Before rebooting the system, read through the next few sections for some more information and possible issues you may run into. If you don't want to read anymore, reboot the system and happy hacking!

Flashing the Kernel (non-free)

If you don't wish to run a free system, you can steal the kernel from the ChromeOS kernel partition like so:

• Run the following command to flash the kernel to the kernel partition:

  # dd if=root/boot/vmlinux.kpart of=/dev/sda1
  

• NOTE: Remember to change /dev/sda1 to the appropriate value for your device!

• Unmount the device:

  # umount root
  

• Sync the system for good measure:

  # sync
  

At this point you should have a working Dragora 3 install. Before rebooting the system, read through the next few sections for some more information and possible issues you may run into. If you don't want to read anymore, reboot the system and happy hacking!

Booting with Linux-libre

Let me guess, you tried to boot your new fully-free system and it didn't work. You got stuck at a white screen. This is actually a good thing! This is currently one of the major bugs with using Linux-libre (see Bugs). This bug is super annoying and will probably take you forever to get past it. Try the following:

• Power off the device.
• Unplug all external devices. (SD Card and thumb drives)
• Reset the system by holding the refresh and power keys.
  • The system will reboot and the screen will turn off quickly. Note that the power LED will remain on as long as you hold the power key.
• Plug in the media you wish to boot off and power on the device.
  • You should get "stuck" on the white screen again. Wait approximately 2-3 minutes and hopefully it will boot.
  • If it doesn't boot, try these steps again. It may take a couple (it took me 4-5) tries until the system boots.

Creating a Bootable Kernel

There are a few things you're going to need in order to create your own Linux-libre binary. I'll explain this just in case I don't update to the version that you wish to use. This will give you the freedom to choose whatever version of Linux-libre you want! Firstly, you will need a copy of Linux-libre, whether from source or just binary forms. If you choose the binary forms, make sure that there is AT LEAST a vmlinuz or zImage AND dtbs directory. You will need them! If you choose to compile from source be sure to do make ${MAKEFLAGS} zImage modules dtbs to create the dtbs directory and the zImage file.

Once you have a the necessary items from the kernel itself, you will need to get a hold of a few items.

• vbutil_kernel
  • This program will create signed kernels for you to boot.
  • It can be obtained from the default ChromeOS install on the eMMC or from your package manager usually under the name vboot-utils.
• mkimage
  • This will make the image for vbutil_kernel to sign.
• All the items in this repo
  • kernel.keyblock and kernel_data_key.vbprivk for kernel signing
  • config.txt for proper booting
  • kernel.its to create the correct image for the C201 (may need modified)
  • make-c201-kernel.sh to make it all work

Once you've collected all of the programs and files listed you can run the make-c201-kernel.sh script and it should create a kernel that you can copy to the kernel partition of your external media. Make sure to double check that everything is correct for your system and device before running it! Simply run # dd if=newkernel of=/dev/${kernel-partition} replacing ${kernel-partition} with the correct partition.

Obtaining vbutil_kernel

As mentioned, you can obtain this program by installing a package usually called vboot-utils. However, I imagine that you don't have this program nor care about it enough to try and build it for Dragora. Luckily, you can easily get it by copying it from ChromeOS. While on an externally booted system just do the following:

# mount -o ro /dev/mmcblk0p3 /mnt
# cp /mnt/usr/bin/vbutil_kernel /usr/bin
# rsync -a /mnt/usr/share/vboot /usr/share
# umount /mnt

The second to last step will give you access to those kernel signing files from before (kernel.keyblock and kernel_data_key.vbprivk). It is also a good idea to obtain dump_kernel_config for dumping the command line, not the kernel config. It makes more sense to use this when scripting. Obtain it like this:

# cp /mnt/usr/bin/dump_kernel_config /usr/bin

Installing to the eMMC (NOT TESTED)

As the header suggests, this section is purely theoretical and hasn't been tested yet. According to Debian, installing onto the eMMC requires you to simply copy everything off your external media. Boot on your external media and follow these steps to do so:

• Start by shrinking the ROOT-A and ROOT-B partitions:

  # cgpt add -i 3 -s 32 /dev/mmcblk0
  # cgpt add -i 5 -s 32 /dev/mmcblk0
  

• Expand the STATE partition:

  # cgpt add -i 1 -b 282688 -s 30470080 /dev/mmcblk0
  

• Reformat the partition to ext4:

  mkfs.ext4 /dev/mmcblk0p1
  

• Copy everything on your external media (be patient, this will take a while):

  # mount -t ext4 /dev/mmcblk0p1 /mnt
  # cp -ax / /mnt
  # umount /mnt
  

• According to Debian, you need to reconfigure the kernel. I'm not sure if this is actually necessary, thus, I won't put it here yet.

• Flash your kernel to the eMMC's kernel partition:

  # dd if=/mnt/boot/yourkernel of=/dev/mmcblk0p2
  

• Also according to Debian, you also should set the priorities of the kernel partitions:

  # cgpt add -i 2 -P 10 -S 1 /dev/mmcblk0
  # cgpt add -i 4 -P 0 -S 0 /dev/mmcblk0
  

In theory, you should now be able to boot off the eMMC onto your new Dragora system!

Bugs

• White screen booting issue
  • See Booting with Linux-libre for information.
• No eMMC recognition.
  • Debian has a fix for this, however, I haven't got it working yet.

Sources

• https://archlinuxarm.org/platforms/armv7/rockchip/asus-chromebook-flip-c100p#installation
• https://wiki.debian.org/InstallingDebianOn/Asus/C201
• https://plus.google.com/+OlofJohansson/posts/34PYU79eUqP
• https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/custom-firmware
• Some dude from freenode #parabola