RW_LEGACY or BOOT_STUB – which one to choose?

John’s custom SeaBIOS is able to modify a Chromebook’s BIOS so that it can boot from a USB drive in order to install Linux. Some of you may be wondering, what’s the difference between the RW_LEGACY and BOOT_SLOT BIOS mods?

Although John has explained the differences I thought it would be helpful to reiterate them since I’ve noticed that this question is a reoccurring one amongst commenters.


Using the RW_LEGACY modified BIOS allows you to dual boot Chrome OS and Linux. You can also wipe Chrome OS completely and run Linux on its own if you prefer. Every time you turn on the Chromebook you will need to do the following:

  • To get to Chrome OS you have to press CTRL + D at the initial Chrome screen.
  • To boot Linux you have to press CTRL + L at the initial Chrome screen and then press ESC at the SeaBIOS screen and choose the drive to boot from.

RW_LEGACY is the best option if you’re not comfortable with opening up the Chromebook to disable write protect and are worried about bricking the device. With RW_LEGACY you can’t brick the device and don’t need to disable write protect.


Some people prefer not to press key combinations at boot, so using the BOOT_STUB mod is the better option.

If you choose the BOOT_STUB option the boot process is modified so that you only get the SeaBIOS screen and after a sec or two Linux boots up directly without the need to press any keys. This is the option if you want to wipe Chrome OS entirely and just boot Linux.

For this option you’ll need to roll up your sleeves and disable write protect by removing the Chromebook’s back cover. This carries the risk of bricking your device or damaging the Chromebook’s motherboard when you open it up.

In my opinion the risk of damage is minimal as long as you are careful and follow the instructions provided. After having opened my Chromebook several times to make how to videos I can report that no damage has occurred (I hope I’m not tempting fate!).

For those readers that are not confident with doing this, stick to the RW_LEGACY option, you’ll still be able to run Linux and pressing a few key combinations on startup is only a minor nuisance.



  • Found out the third field is for the RIGHT alt key, and not the LEFT alt key. So, problem solved! 🙂

  • Hello again Captain! Having established dual boot with mint 18.1, I now need to have the function keys work as traditional F1, F2, etc. Then I would like to have the special keys such as browser forward/backward when I press alt-1 for backward and alt-2 to forward. So yes, that would be alt combined with the respective number keys 1 and 2, and not the top row function keys.

    I changed /usr/share/X11/xkb/symbols/pc to

    key { [F1] }
    etc. and I get my function keys back, as desired

    But then, in order to get special keys by mapping alt-,
    I tried changing /usr/share/X11/xkb/symbols/us from:

    key { [ 1, exclam ] };
    key { [ 2, at ] };


    key { [ 1, exclam, XF86Back ] };
    key { [ 2, at, XF86Forward ] };

    shift-1 and shift-2 still map to “!” and “@”, respectively, but alt-1 and alt-2 do NOT map to the special keys to make the browser go forward and backward as desired. According to xkb docs, ‘alt’ is mapped to the third field, in this case XF86Back and XF86Forward, respectively.

    Can you suggest what I need to try? THANK YOU!


  • Got my Chromebook today, the CB5-571-C09S and followed your instructions for setting up dual-boot and installing Mint from your other page. Worked flawlessly! Thank you Captain! Well done videos!

  • Awesome videos and instruction, Captain! Do you know if the seaBios mod is compatible with Chromebook 15 CB5-571-C09S? I didn’t see that model listed on John’s compatibility list. THANKS!

  • When booting from usb CB just hangs with message “booting from usb”. anyone dealt with the problem b4?

      1. it is a brand new sandisk 3.0 usb drive, and i have used the dd method as described in the bootable linux USB. I do appreciate the fast response however. i will go buy a different model and see if that helps . Will report afterwards, Thank you

  • I’m currently trying to put Linux onto a Toshiba Chromebook 2 (Baytrail – Swanky)

    I want to get rid of ChromeOS so I have more space on the internal storage. How can this be done using Boot_Legacy?

    Also, this model in the ‘supported models matrix’ on John Lewis’ site shows ‘yes’ only under the Boot_Legacy column. However it seems you have the same model and you’ve used the Boot_Stub?

  • Hello Captain, big fan of yours btw! So if its not much trouble and when its convenient for you I hope you wouldn’t mind terribly, to take the time to answer a few questions for me, I would be very greatful? Thank you in advance…

    [ Question 1 ] If I choose to use Boot_Stub, will that also entirely erase the possibility of me ever being able to return to using chrome OS? I understand it will take the {scary chrome os is missing!} screen, but does it actually mean you terminated any other way of flashing back to chrome os?

    [ Question 2 ] If it bricks my device, is their anyway to unbrick it with returning to stop, what does a bricked chromebook mean eactly, because in the android field, a bricked device, can always be unbricked with the correct software , stock roms and recovery ,etc..

    And last but not least….

    [ Question 3 ] I am running a Acer Chromebook 15 {CB3-531} banjo. their are literaly no instruction videos on youtube on my model, on any subject it seems, rather its crouton or changing the os, so could you give me some feedback on CB, if you had any information. I have ran crouton, and I finaly got to a comfortable experience usin it, I even went as far as being able to use abd for my android through the xfce4 trusty desktop, with surprising simplicity, but trying to run that does not leave much space. Please feel free to email me. Thankyou.

    1. Glad you like my site Patrick, really appreciate your support!

      On to your questions:
      Firstly, there is a new BIOS mod I would recommend going forward by Mr Chromebox ( It has better support and is more intuitive to use.

      1) Yes you can always go back to ChromeOS after using the boot_stub version. You would just run the script in a terminal and choose to restore the stock firmware. After a reboot you would have to go through the normal ChromeOS recovery.

      2) I haven’t got any experience in the ‘my CB is bricked’ area, although I’ve read various posts on John’s site about people unbricking their devices using some extra equipment. I believe that Mr Chromebook also offers a service to unbrick devices (see previous link). My personal experience is that I have modded and re modded my CB’s BIOS over and over and have had no issues.

      3) Your CB is supported and you should have no problems with installing Linux using the boot_stub option. Be aware that you need to remove the write protect screw which will be similar procedure to my first video

      Hope that helps and happy modding!

  • Hi Captain, if we wipe ChromeOS completely, do we have to do the “ctrl + L or ctrl + D” thing or not ? Thanks for all !

  • Thanks Captain for the link! I used it and it works like a charm. I don’t need to replace the MMC now as I have a plugged 64GB usb at all times. Not only it skips the USB read, but also I was able to remove the ChromeOs bitmat using the code.
    Thanks again and please continue doing such a great work for the community!

  • Hi captain I have a dell chromebook where I upgraded the ssd to 512gb I want to make this ssd the main one for my linux personal files as well as it being my “c” drive. How should I go about it and yes the distro I want is linux mint.

  • Hey Captain! Thanks for the great post!
    I managed to get a single Linux Mint Mate 18 on the Acer CB3-111.
    I cannot upgrade the chromebook so I am stuck with the 16 GB MMC. However, I use a 64 GB usb plugged in all the time.
    The problem that I experience is that when I boot, it looks into the USB and doesn’t boot into the linux.
    Instead, I have to remove the usb and hard reboot.

    Do you know, where and how I can change the boot options so that I can skip the USB check on startup?
    Thanks a lot!

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