Debug Button Shortcuts

Chrome OS devices provide a variety of advanced keyboard and button shortcuts that are useful for debugging. We document those here, as well as highlight some differences between devices with and without keyboards.

Devices With Keyboards

See the official support page for non-debug keyboard shortcuts.

Note that some of the below debug keyboard shortcuts are implemented at a very low level and are not keyboard-layout aware. When in doubt, assume debug shortcuts refer to the physical mapping of a US keyboard layout.

Shortcuts with an asterisk (*) also work with tablets/detachables with a keyboard attached.

Notes:

• AP = Application Processor; EC = Embedded Controller.
•  EC hibernate is supported only on devices with select Embedded Controllers.
• Alt + Volume-Up is treated as the Magic SysRq key. When in Developer mode, you can enable SysRq key combinations as documented in the Linux kernel docs.
• Overriding the charging port is only supported on Samus.

Firmware Keyboard Interface

• Recovery mode: Hold Esc + Refresh and press Power.

  • From here, follow the instructions at https://google.com/chromeos/recovery to recover your device using external media.

• Recovery mode: Engage the small Reset pinhole with a paperclip, hit Power and continue engaging Reset for 2 seconds. Typically (only?) for chromeboxes with a QWERTY keyboard attached.

  • From here, follow the instructions at https://google.com/chromeos/recovery to recover your device using external media.

• Developer mode: To enter Developer Mode, first enter recovery mode, then press Ctrl + D, followed by Enter to accept.

  • Note that Developer Mode disables security features and may leave your device open to attack. Only enable if you understand the risks.
  • Devices in Developer Mode will show a warning screen on every boot. The screen will time out after 30 seconds, playing a warning beep.
  • From the warning screen, the following keyboard shortcuts are available:
    • Ctrl + D: Boot the system from the internal disk.
    • Ctrl + U: Boot the system from an external USB stick or SD card. The option crossystem dev_boot_usb=1 must be set from the command line before this option is available.
    • Ctrl + L: Chain-load an alternative bootloader (e.g. SeaBIOS). This may allow booting other Operating Systems more easily. Not all devices are shipped with alternative bootloaders. New alternative bootloaders can be manually installed on the device from Developer Mode. The option crossystem dev_boot_legacy=1 must be set from the command line before this option is available.
    • 0 through 9: On newer (2019+) platforms, more than one alternative bootloader can be installed and Ctrl + L will show a selection menu. On these devices, the number keys can be used to directly boot the numbered bootloader without going through the menu.
  • The option crossystem dev_default_boot=usb can be set to override the default boot behavior if no key combination is pressed for 30 seconds.

Some devices do not support Esc + Power + Refresh for entering Recovery Mode:

• Chromeboxes have a recovery button. To enter Recovery Mode, hold down the recovery button and press Power.
  • To enter Developer Mode on a Chromebox, first enter recovery mode and press Ctrl + D on the keyboard, then push the physical recovery button on the Chromebox to accept.
• Older devices have a physical Developer Mode switch. You can read up on your particular device under the device-specific developer information table.

Note: An additional, deeper reset (with forced memory retraining) can be triggered on some devices on the way to recovery mode by holding Left-Shift during the normal recovery sequence (i.e., Left-Shift + Esc + Refresh + Power).

Devices Without Keyboards

Shortcuts

Starting in 2018, keyboardless Chrome OS devices are being built, in tablet and detachable form factors. Without a keyboard, some typical keyboard-based debugging shortcuts can't be supported. Below are the shortcuts for performing various system and debugging tasks with only the limited physical buttons and touch screen found on tablets or detachable devices.

Note that some of the following behaviors work on convertible devices when used in tablet mode.

Notes:

• Filing feedback from the power button menu is currently (as of 2018-10-19) only supported on canary (for all users) and dev/beta/stable (for Google employees) release channels. All users can still file feedback via the browser options menu (Help > Report an issue...).
• Battery cutoff shortcut is supported only on devices with a smart battery (e.g., not Scarlet, Dru).

Firmware Menu Interface

The boot firmware screen is accessible through keyboard shortcuts on devices with keyboards; on keyboardless devices, the following methods are supported:

• Recovery mode: Power + Volume-Up + Volume-Down, hold for 10 seconds. If the screen turns off or on during that period, ignore it and make sure you keep all three buttons held down for the whole 10 second period, then release them.
  • From here, follow the instructions at https://google.com/chromeos/recovery to recover your device using external media.
  • To change the UI language or display additional debugging information, you can press either Volume-Up or Volume-Down. This leads to a menu that can be navigated with the volume buttons, and menu items can be selected with the power button.
• Developer mode: Enter recovery mode and press Volume-Up + Volume-Down simultaneously, then select “Confirm Enabling Developer Mode” in the menu.
  • Note that Developer Mode disables security features and may leave your device open to attack. Only enable if you understand the risks.
  • Devices in Developer Mode display a similar menu on every boot that allows selecting developer boot options. The menu will time out and boot after no key has been pressed for 30 seconds, playing a warning beep.
  • The “USB or SD card” and “Legacy BIOS” boot menu options need to be enabled on the command line before they work, same as with the firmware keyboard UI.
  • In addition to selecting boot options in the menu, the following shortcut combinations are available in the developer warning menu:
    • Press Volume-Down for 3+ seconds, then release: Boot the system from the internal disk.
    • Press Volume-Up for 3+ seconds, then release: Boot the system from an external USB stick or SD card.
    • If a keyboard is connected, all boot shortcuts from the firmware keyboard UI are also available in the developer warning menu.

Note: An additional, deeper reset (with forced memory retraining) can be triggered on some devices on the way to recovery mode by holding Power + Volume-Up + Volume-Down for 30 seconds (until the LED starts flashing).

EC Debug Mode

Not all debugging shortcuts are implemented with a simple combination of buttons—some are found by utilizing multi-button sequences, initiated after entering a special EC state called “debug mode”. To enter debug mode, press Volume-Up + Volume-Down for 10 seconds. Release once the charging LED starts flashing. Once in debug mode, any of the following actions can be taken, using Volume-Up (U) and Volume-Down (D) buttons.

Supported codes:

Debug mode is canceled when a sequence finishes, or after 10 seconds without a volume button press.