How to make SeaBIOS the default on your Acer C720

Divulged this evening by Duncan Laurie on the coreboot mailing list:

If you want to boot SeaBIOS by default and you have unlocked the SPI flash write protection you can set flags in the (write protected) “GBB” flash region that will make it boot legacy mode by default.

In Chrome OS there is a script called that will do this for you. Run the script with no arguments to get a list of possible flags and then to enable short dev mode screen (1 second timeout) followed by default legacy mode boot you could use these flags:


/usr/share/vboot/bin/ 0x489

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79 thoughts on “How to make SeaBIOS the default on your Acer C720”

  1. I’m coming across a problem where I do this, it displays the correct hex 1e9 as the gbb flag, but will still look for the chrome os. I still have to press ctrl+l every time, but now I have to do it within a second of it posting. I don’t get it.

  2. This sounds like a SPAM comment. The exact command is given, but, you need to have developer mode enabled. That’s covered on the ChromiumOS website. Search.

  3. Thank you so much for publishing this info. Would you be willing to write out the exact commands needed to execute these changes? I have limited command line experience.


  4. If you hold down ctrl + D at the boot screen (I think) it will attempt to boot ChromeOS. You can then recover and use the gbb_flags script to set the flags back to 0 i.e. 0x000

  5. Hello.

    I’ve tried it and it works fine.
    But now I want go back to only ChromeOs.
    How can I reset the Bios-Settings?
    Can anyone help me?


  6. If you aren’t getting a “ChromeOS is missing or damaged screen”, it means you’re still using one of my custom ROM’s. You flash the backup back using “./flashrom -w backup-date.rom” while cd’ed into the directory the USB stick is mounted on.

  7. Ok
    I will try a gain soon and write down exactly the steps I took, I know its not very clear now.
    How do I determine which ROM I am using?


  8. That doesn’t make a lot of sense to me. If you have written the backup ROM back to the device, using Flashrom, you will be able to load ChromeOS from a recovery, and so also boot ChromeOS. Please indicate which ROM your Chromebook is currently running.

  9. yes I do and I can install chrome os back, the issue is I am not sure how to undo the script, it wont let me log back into the command line with any keyboard shortcuts.
    and so chrome os will not boot

  10. Hi I have followed the procedure as stipulated here and it works. However now I would like to restore the device to factory settings.

    Does anyone know the procedure?

    Thank you

  11. Hello. You are doing some neat stuff. I set my daughter up with an ACER C720 for Christmas. It is running Ubuntu 14, not a dual boot though. I would like to get rid of the scary screen though because my daughter has already once wiped every thing clear by hitting the space bar instead of ctrl-L.

    Can I set these flags in Ubuntu or do I have to be in ChromeOS? I have a recovery image of ChromeOS and am prepared to start over if necessary but it would sure be nice if I didn’t have to.


  12. It is okay to change the flags before OS install. If your battery dies again, you will lose the GBB flags you’ve set, but you can set them again with a ChromiumOS USB stick instead of wiping your beloved distro off. It’s a “feature” of the original C720 firmware.


    Perhaps you should consider the custom firmware I provide, which will get rid of the ChromeOS specific stuff completely, and make your Chromebook behave like a conventional laptop.

  13. Hey John. Thank you for the article, this looks like exactly what I’m looking for. However, I’m still having some issues I’m wondering if you could give me some advice on, please:

    I originally found this post after having my c720 with Elementary OS installed on it die after I let the battery die and reset the settings regarding legacy boot. Should’ve been no problem to put back, but I haven’t been able to install Elementary OS without it corrupting my Chrome OS installation. So, two questions:

    Is it ok to carry out what you’ve detailed in this post before installing another OS, and will it stick if Chrome OS gets messed up? I’m worried about resetting these flags and then having the Elementary installation mess up and then not being able to get into any OS at all because it defaults to a legacy boot.

    Is there a way that you know of to either edit these flags or edit the legacy boot settings from the Chrome BIOS? Pressing TAB at the Scary Spacebar Screen gives me information on both of these but doesn’t let me edit them.

    Cheers for any help. I’m determined to make my cheap Chromebook into a reliable Linux machine that doesn’t randomly render my whole installation inaccessible when the battery dies!

  14. Thank Duncan Laurie, I just parroted his info.

    You can run it from within a ChromeOS image. There’s an article on here about extracting one. Then it’s just like chrooting into any other Linux image – bind mount dev proc and sys, and then chroot.

    It kind of stopped with the C720/HP14. We’ll have to see what the Broadwell based Chromebooks bring, next year, but sockets and connectors cost money, and Chromebooks are all about saving it. My recommendation is not to get too hung up on upgrading the interior storage – I’ve been running my HP14 with the original SSD and a *really* slow 128GB USB 3.0 stick, mounted to Downloads, the last 6 weeks, and it’s an almost undistinguishable experience from the upgraded SSD (which eventually b0rked) the previous 6 months.

    Stay away from the Baytrail/ARM Chromebooks. Although the high IPS screens are really nice, the processors are way too slow and more suiting of a mobile phone. Broadwell will be the one to watch.

  15. Thank you for your article.

    Is there any way of doing this from Linux (Ubuntu)? I don’t seem to have ChromeOS any more? Can we just download the script and run it or does it call other stuff?

    I just wanted to have an easy to use Linus laptop where I don’t have to worry about the battery running flat and then losing my Linux environment (this happened to me a while back).

    Cheers Mike

    PS Are there other chromebooks that allow you to upgrade the SSD and come with a processor that’s easy to use with Linux. I quite like the Celeron the C720 comes with but would prefer nicer hardware like the original Toshiba 13″ but sadly the SSD is fixed. 4GB RAM would also be nice.

  16. Unable to 0x489, keep getting an error:
    /usr/bin/old_bins/ 109: flashrom: not found


    chronos@localhost / $
    Changes ChromeOS Firmware GBB Flags value.

    Usage: /usr/bin/old_bins/ [option_flags] GBB_FLAGS_VALUE

    Defined flags (some values may be not supported by all systems):


    To get a developer-friendly device, try 0x11 (short_delay + boot_usb).
    For factory-related tests (always DEV), try 0x39.

    -d,–[no]debug: Provide debug messages (default: false)
    -f,–file: Path to firmware image. Default to system firmware. (default: ”)
    –[no]check_wp: Check write protection states first. (default: true)
    -h,–[no]help: show this help (default: false)
    chronos@localhost / $ 0x489
    /usr/bin/old_bins/ 109: flashrom: not found

  17. The script has moved to /usr/share/vboot/bin/ and the flashrom command isn’t in your PATH by default so…

    export PATH=/usr/sbin:$PATH
    sudo /usr/share/vboot/bin/ 0x489

  18. I have the impression that functionality may have been moved into another script which *is* in (/usr)/(s)bin somewhere. If you could find it and tell me what it is, I can update the article accordingly.

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