Install

This is a guide on installing GrapheneOS for the officially supported devices. It can be followed for both the official releases and custom builds.

Table of contents

Prerequisites

You should have at least 2GB of free memory available.

You need one of the officially supported devices. To make sure that the device can be unlocked to install GrapheneOS, avoid carrier variants of the devices. Carrier variants of Pixels use the same stock OS and firmware with a non-zero carrier id flashed onto the persist partition in the factory. The carrier id activates carrier-specific configuration in the stock OS including disabling carrier and bootloader unlocking. The carrier may be able to remotely disable this, but their support staff may not be aware and they probably won't do it. Get a carrier agnostic device to avoid the risk and potential hassle. If you CAN figure out a way to unlock a carrier device, it isn't a problem as GrapheneOS can just ignore the carrier id and it's otherwise the same.

It's best practice to update the stock OS on the device to make sure it's running the latest firmware before proceeding with these instructions. This avoids running into bugs, missing features or other differences in older firmware versions. Early Pixel 2 and Pixel 2 XL bootloader versions use a non-standard unlocking system not covered by these installation instructions. You can either update the device via over-the-air updates or sideload a full update, which for Pixel phones can be obtained from the full update package page.

Obtaining fastboot

You need an updated copy of the fastboot tool and it needs to be included in your PATH environment variable. You can run fastboot --version to determine the current version. It should be at least 28.0.2. You can use a distribution package for this, but most of them mistakenly package development snapshots of fastboot, clobber the standard version scheme for platform-tools (adb, fastboot, etc.) with their own scheme and don't keep it up-to-date despite that being crucial.

List of distributions with proper packages:

If your distribution doesn't have a proper fastboot package, which is likely, consider using the official releases of platform-tools from Google. You can either obtain these as part of the standalone SDK or Android Studio which are self-updating or via the standalone platform-tools releases. For one time usage, it's easiest to obtain the latest standalone platform-tools release, extract it and add it to your PATH in the current shell. For example:

unzip platform-tools_r29.0.6-linux.zip
export PATH="$PWD/platform-tools:$PATH"

Sample output from fastboot --version afterwards:

fastboot version 29.0.6-6198805
Installed as /home/username/downloads/platform-tools/fastboot

Don't proceed with the installation process until this is set up properly in your current shell. A very common mistake is using an outdated copy of fastboot from a Linux distribution package not receiving regular updates. Make sure that the fastboot found earliest in your PATH is the correct one if you have multiple copies on your system. The fastboot --version output includes the installation path for the copy of fastboot that's being used. Older versions of fastboot do not have support for current devices and OS versions. Very old versions of fastboot are still shipped by Linux distributions like Debian and lack the compatibility detection of modern versions so they can soft brick devices.

Obtaining signify

To verify the download of the OS beyond the security offered by HTTPS, you can use the signify tool. If you do not have a way to obtain signify from a package repository you're already trusting, it does not make sense to use it. GrapheneOS releases are hosted on our servers and we do not have third party mirrors. A compromised signify would be able to compromise your OS and the GrapheneOS download due to the lack of an application security model on traditional operating systems. It would be worse than not trying to verify the signatures. It's far less likely that our servers would be compromised than someone's GitHub account or GitHub itself. You're already trusting these installation instructions from our site, which is hosted on the same static web server infrastructure as the releases.

On many distributions, signify is available via a signify package in the official repositories. On Debian-based distributions like Ubuntu, the package and command were renamed to signify-openbsd. Following Debian tradition, the signify package and command are an unmaintained mail-related tool for generating mail signatures (not cryptographic signatures) with the final 3 releases from 2003-2004 made directly by the developer via the Debian package without upstream releases. This is clearly not what you want, but it's easy to end up trying to use it instead of signify-openbsd.

Enabling OEM unlocking

OEM unlocking needs to be enabled from within the operating system.

Enable the developer options menu by going to Settings ➔ About phone and pressing on the build number menu entry until developer mode is enabled.

Next, go to Settings ➔ System ➔ Advanced ➔ Developer options and toggle on the 'Enable OEM unlocking' setting. This requires internet access on devices with Google Play Services as part of Factory Reset Protection (FRP) for anti-theft protection.

Unlocking the bootloader

First, boot into the bootloader interface. You can do this by turning off the device and then turning it on by holding both the Volume Down and Power buttons.

The bootloader now needs to be unlocked to allow flashing new images:

fastboot flashing unlock

The command needs to be confirmed on the device.

Obtaining factory images

The initial install will be performed by flashing the factory images. This will replace the existing OS installation and wipe all the existing data.

You can either download the files with your browser or using a command like curl. It's generally easier to use the command-line since you're already using it for the rest of the installation process, so these instructions use curl.

Download the factory images public key (factory.pub) in order to verify the factory images:

curl -O https://releases.grapheneos.org/factory.pub

This is the content of factory.pub:

untrusted comment: GrapheneOS factory images public key
RWQZW9NItOuQYJ86EooQBxScfclrWiieJtAO9GpnfEjKbCO/3FriLGX3

The public key has also been published via the official @GrapheneOS Twitter account, the /u/GrapheneOS Reddit account and is available on GitHub. When the current signing key is replaced, the new key will be signed with it.

Download the factory images for the device from the releases page. For example, to download the 2020.04.14.23 release for the Pixel 3 XL (crosshatch):

curl -O https://releases.grapheneos.org/crosshatch-factory-2020.04.14.23.zip
curl -O https://releases.grapheneos.org/crosshatch-factory-2020.04.14.23.zip.sig

Verify the factory images using the signature:

signify -Cqp factory.pub -x crosshatch-factory-2020.04.14.23.zip.sig && echo verified

This will output verified if verification is successful. If something goes wrong, it will output an error message rather than verified.

Flashing factory images

Reboot into the bootloader interface to begin the flashing procedure.

Next, extract the factory images and run the script to flash them. Note that the fastboot command run by the flashing script requires a fair bit of free space in a temporary directory, which defaults to /tmp:

unzip crosshatch-factory-2020.04.14.23.zip
cd crosshatch-qq2a.200405.005
./flash-all.sh

Use a different temporary directory if your /tmp doesn't have enough space available:

mkdir tmp
TMPDIR="$PWD/tmp" ./flash-all.sh

Wait for the flashing process to complete and for the device to boot up using the new operating system.

You should now proceed to locking the bootloader before using the device as locking wipes the data again.

On current generation devices like the Pixel 3, Pixel 3 XL, Pixel 3a and Pixel 3a XL, you'll need to reboot from the userspace fastbootd mode to the bootloader by selecting Reboot to bootloader from the fastbootd menu using the volume keys and the power button in order to continue the installation.

Troubleshooting

A majority of failed flashes tend to be caused by substandard USB connectors, plugging in via hubs or bad cables which aren't properly up to the USB standard. The scrollback from a failed flash will contain valuable diagnostic information which is essential in knowing where and how the process went wrong.

Front I/O ports on desktop computer cases and USB 3.1 or USB C on many laptops often aren't implemented properly or are broken in subtle ways, which may cause flashing to fail even on a USB port that works for other peripherals. Older Linux kernels that predate version 5 may have inadequate or patchwork support for USB C or USB 3. If you are installing from a Linux distribution, ensure your distribution uses a modern kernel.

Always use a high quality USB A to USB C cable with a rear USB port directly on your motherboard, and never use a USB hub for flashing. Never install from a virtual machine; USB passthrough in software emulation may be broken or inadequate and this can cause the flashing to fail.

Locking the bootloader

Locking the bootloader is important as it enables full verified boot. It also prevents using fastboot to flash, format or erase partitions. Verified boot will detect modifications to any of the OS partitions (vbmeta, boot/dtbo, product, system, vendor) and it will prevent reading any modified / corrupted data. If changes are detected, error correction data is used to attempt to obtain the original data at which point it's verified again which makes verified boot robust to non-malicious corruption.

In the bootloader interface, set it to locked:

fastboot flashing lock

The command needs to be confirmed on the device since it needs to perform a factory reset.

Unlocking the bootloader again will perform a factory reset.

Disabling OEM unlocking

OEM unlocking can be disabled again in the developer settings menu within the operating system after booting it up again.

Verifying installation

Verified boot authenticates and validates the firmware images and OS from the hardware root of trust. Since GrapheneOS supports full verified boot, the OS images are entirely verified. However, it's possible that the computer you used to flash the OS was compromised, leading to flashing a malicious verified boot public key and images. To detect this kind of attack, you can use the Auditor app included in GrapheneOS in the Auditee mode and verify it with another Android device in the Auditor mode. The Auditor app works best once it's already paired with a device and has pinned a persistent hardware-backed key and the attestation certificate chain. However, it can still provide a bit of security for the initial verification via the attestation root. Ideally, you should also do this before connecting the device to the network, so an attacker can't proxy to another device (which stops being possible after the initial verification). Further protection against proxying the initial pairing will be provided in the future via optional support for ID attestation to include the serial number in the hardware verified information to allow checking against the one on the box / displayed in the bootloader. See the Auditor tutorial for a guide.

After the initial verification, which results in pairing, performing verification against between the same Auditor and Auditee (as long as the app data hasn't been cleared) will provide strong validation of the identity and integrity of the device. That makes it best to get the pairing done right after installation. You can also consider setting up the optional remote attestation service.

Replacing GrapheneOS with the stock OS

Installation of the stock OS via the stock factory images is the same process described above. However, before locking, there's an additional step to fully revert the device to a clean factory state.

The GrapheneOS factory images flash a non-stock Android Verified Boot key which needs to be erased to fully revert back to a stock device state. After flashing the stock factory images and before locking the bootloader, you should erase the custom Android Verified Boot key to untrust it:

fastboot erase avb_custom_key