What is De-Chroming?
This talk is an instructional companion to the SFLC @ 10 Disposable Computing talk.
De-Chroming is the process of taking a Chromebook laptop, in this case the Acer c720, and replacing the Chrome operating system with a full-featured Debian install.
Why would you De-Chrome a laptop?
Perhaps you want access to all the great programs in Debian, perhaps you want a high security computer for use doing humanitarian work in hostile conditions, or perhaps you just want to tinker with some cool new hardware. There are many reasons you might be interested.
What do you need?
- A small Philips-head screwdriver
- A USB flash drive or an SD card with 100 megabytes free
- A chromebook (this guide is for the Acer c720 model but other models are supported)
- A wireless network
How to De-Chrome the c720 in 10 simple steps
This series of steps is designed to replace the default coreboot BIOS shipped on the laptop with a community-built version. This process brings a theoretical risk of bricking your device, which would require ~$50 of hardware and some technical knowledge to repair. You should be safe if you read all the instructions carefully but, if you would like to know more, take a look at the community wiki.
- Start the computer and log in to the chromebook guest account.
- Activate developer mode (note: this will delete all the user data on the machine so if you have been using the laptop you should back up your documents first).
- When you are logged in hold down Escape+Refresh(F3) and press the power button to reboot into recovery mode.
- Press Ctrl+D at the Recovery screen and then confirm that you would like to activate developer mode.
- Wait as it reboots and switches to developer mode, then shut down the machine.
- Remove write-protect screw as shown in: this video (available as mp4 or mkv).
- Reboot and re-log in as guest.
- Press Ctrl+Alt+t to get a Google terminal.
- In that terminal type "shell" to gain access to the full set of capabilities.
- Plug in your USB thumbdrive or insert your SD card.
- Run this command, which will download a script. (enter this as one unbroken line):
Press 4 to backup your old BIOS and press 5 to install a community version from John Lewis.
cd; rm -f flash_chromebook_rom.sh; curl -k -L -O https://johnlewis.ie/flash_chromebook_rom.sh; sudo -E bash flash_chromebook_rom.sh
- Once that has completed successfully and without errors, reboot. Now you can install Debian or your free software distribution of choice. If you received errors, do not reboot and seek help from the coreboot on chromebooks community.
Installing free software
Once you have replaced the default BIOS you will be able to boot from a USB device and install whatever version of a free software operating system you have handy. Everything on the c720 except for the bluetooth is supported with free software drivers so installation should be straightforward, though you may need to install the most recent kernel from your distribution to enable support for the trackpad. Some tips and tricks for dealing with any hardware issues you may run into are available from Kevin Keijzer's blog on the FSFE site.
As with all of our SFLC machines, we install Debian and use the Debian installer to encrypt the hard drive. I am happy to report that that works perfectly well here whether you are installing to the internal drive or to an external USB thumb drive or SD card. That is important since, for most people, the only thing to consider when De-Chroming one of these laptops is what to do with the hard drive.
What to do with the hard drive
To keep costs down, Chromebooks are sold with hard drives that may be too small for most people to comfortably use as their only storage, generally 16 or 32 gigabytes. Those of us De-Chroming the laptops have a few general options for how to deal with this potential limitation: use it as is, replace the drive, or add extra storage with a USB drive or an SD card.
Use as is
16 GB is plenty of space for a Debian install, even using some for swap. This is especially true if you want to have your home partition on a separate thumb drive or SD card. This is also the cheapest and most straightforward option so, if cost is a factor or you just want to test out different versions of linux on the laptop, you should have plenty of space and can always expand it later.
Replace the drive
Larger SSDs are available for ~$50-60 online so if you want more space it is simple enough to just get a larger drive. Just make sure the disk you buy is compatible with the c720 laptop since there are a number of different format options available. There are only a couple dozen machines using these disks so far so any website selling them should list which ones are compatible. To replace the drive just open the case the same way you did to remove the write-protect screw and unscrew the one screw holding the drive in.
If I were going to use the laptop as my primary machine this is what I would do.
Expand the storage with USB or SD devices
Since the c720 has both a USB3 port and an SD card slot, it is easy enough to expand your available storage space with removable media. 64gb USB3 drives are available from $30-40 online. If you do not know how much space you will need, 64gb is probably enough space for you.
If you are buying a thumb drive you also have the opportunity to install the whole operating system to the thumb drive and leave no information about you on the laptop. This is particularly useful for people operating in high security situations like those doing humanitarian work in hostile countries, anyone who is worried about bringing a business machine back inside a secure facility, or anyone who is worried about having to decrypt a hard drive when crossing a hostile national boarder. With no information about you or your activities on the device, you can simply leave your laptop at whatever risky location you have traveled to and De-Chrome yourself a new one when you return to safer ground.
Updated July 22, 2015 with options for updated script from John Lewis.
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