CopperheadOS installation instructions

Supported devices

CopperheadOS currently has official support for the following devices:

  • Pixel 2 (walleye)
  • Pixel 2 XL (taimen)
  • Pixel 3 (blueline)
  • Pixel 3 XL (crosshatch)
  • Pixel 3a (sargo)
  • Pixel 3a XL (bonito)
  • Pixel 4 (flame)
  • Pixel 4xl (coral)
  • Pixel 4a (sunfish)

At one point CopperheadOS was supported on the:

  • HiKey (hikey)
  • HiKey 960 (hikey960)
  • Samsung Galaxy S4
  • Nexus 5 (hammerhead)
  • Nexus 5X (bullhead)
  • Nexus 6P (angler)
  • Pixel (sailfish)
  • Pixel XL (marlin)

It can be ported to other Android devices with Treble support via the standard device porting process. Most devices lack support for the security requirements needed to match how it works on the officially supported devices.


You should have at least 4GB of memory on your computer to avoid problems.

You can obtain the adb and fastboot tools from the Android SDK. Either install Android Studio or use the standalone SDK. Do not use distribution packages for adb and fastboot. Distribution packages are out-of-date and not compatible with the latest version of Android. An obsolete fastboot will result in corrupted installations and potentially bricked devices. Do not make the common mistake of assuming that everything will be fine and ignoring these instructions. Double check that the first fastboot in your PATH is indeed from an up-to-date SDK installation:

which fastboot

Installing platform tools on your Mac, Windows or Linux

Download the latest SDK platform-tools directly from Google here

To make your life easier, add the directories to your PATH in your shell profile configuration. This will make it so you do not have to be inside a specific directory to get access to fastboot.

Adding to your $PATH in Mac, Windows and Linux.

Check your $PATH by typing fastboot -h and see if the output matches ..usage: fastboot [OPTION...] COMMAND...

With your $PATH correct and installation complete, you can now flash factory images regardless of the directory.

Setting up the SDK on Linux without Android Studio

To set up a minimal SDK installation without Android Studio on Linux:

mkdir ~/sdk
cd ~/sdk

Run an initial update, which will also install platform-tools and patcher;v4:

tools/bin/sdkmanager --update

For running the Compatibility Test Suite you'll also need the build-tools for aapt:

tools/bin/sdkmanager 'build-tools;25.0.3'

To make your life easier, add the directories to your PATH in your shell profile configuration:

export PATH="$HOME/sdk/tools:$HOME/sdk/tools/bin:$HOME/sdk/platform-tools:$HOME/sdk/build-tools/25.0.3:$PATH"
export ANDROID_HOME="$HOME/sdk"

This is not mandatory, since you can run them from ~/sdk/platform-tools directly.

You should update the sdk before use from this point onwards:

sdkmanager --update

Enabling OEM unlocking

This information covers the Pixel 2, 3 and 3a series of secure phone.

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

Enable the developer settings menu by going to Settings -> About device and pressing on the build number menu entry until developer mode is enabled.

Next, go to Settings -> Developer settings and toggle on the 'Enable OEM unlocking' setting. Certain device models may require connecting to WiFi with a delay before the OEM unlocking setting is toggle-able.

If this setting is grayed out even after connecting to WiFi and selecting/de-selecting Developer Options numerous times, you may have a Bootloader-locked device.

Bootloader-locked devices

Not all devices are created equally and not all devices are unlockable. There is a distinct difference between unlocked devices and bootloader unlockable devices. Often vendors will not know what a bootloader unlockable device is and confuse it with carrier-locked devices. Google has provided refurbished units in the past that are not unlockable even though they may have been unlockable before the refurbished status. To this date no bootloader unlocking exploit has worked or is recommended for installing CopperheadOS. If you encounter a bootloader locked device then you need to return it to the vendor.

Testing the Android bootloader for unlockable compatibility

To test bootloader-unlockable compatibility, use getprop in adb shell

adb shell getprop ro.boot.cid

At the time of this writing the only bootloader unlockable device code is 00000000 (Google)

The following is a non-exhaustive list of locked device codes Copperhead has encountered:

  • VZW_001 : Verizon locked device
  • 00000001 : Google refurbished

Updating stock before using fastboot

It's important to have the latest bootloader firmware before installing CopperheadOS, due to bug fixes for the fastboot mode used to flash CopperheadOS. There are known issues with older versions of the bootloader that are likely to cause problems.

If you're only behind one release, updating within the stock OS makes sense to get an incremental update. If you're behind multiple releases, updating within the OS will usually require installing multiple updates to catch up to the current state of things. The quickest way to deal with that if you have plenty of bandwidth is sideloading the latest full over-the-air update from Google.

Obtaining factory images

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

Latest CopperheadOS images

CopperheadOS currently provides factory images to the Copperhead Partner network and is not open to the public for download.

Legacy installation information (Nexus)

At one point Copperhead supported public downloading of official Nexus factory images on a releases page. Public factory had to be unfortunately images removed because of mass violation of Copperhead's non-Commercial licensing.

Flashing factory images

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. Alternatively, you can use adb reboot bootloader from Android.

Supported devices unlocking directions

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

fastboot flashing unlock

Legacy Pixel 2 XL bootloader unlocking directions

On some older models of Pixel 2 XL it's necessary to unlock the critical partitions.

fastboot flashing unlock_critical

The command needs to be confirmed on the device.

Next, extract the factory images and run the script to flash them. Extracting the factory images depends on the OS you're using and the applications available.

$DEVICE will either be crosshatch, taimen, walleye, sargo, bonito or blueline. The $DATE of the factory image will correspond to our releases.

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:

tar xvf $DEVICE-factory-$DATE.tar.gz
cd $DEVICE-factory-$DATE

Use a different temporary directory if your /tmp doesn't have 2GiB available:

mkdir tmp
TMPDIR=$PWD/tmp ./

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

Pixel 3/3a: setting custom AVB key

The custom AVB key for Pixel 3 and 3a series should automatically be set upon flashing.

Pixel 2 and 2 XL: Setting custom AVB key

On the Pixel 2 and Pixel 2 XL, the public key needs to be set for Android Verified Boot 2.0 before locking the bootloader again

fastboot flash avb_custom_key $DEVICE-avb_pkmd.bin

To confirm that the key is set, verify that avb_user_settable_key_set is yes:

fastboot getvar avb_user_settable_key_set

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 (boot, recovery, 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.

Reboot into the bootloader menu and set it to locked:

fastboot flashing lock

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

Legacy bootloader locking

If your Pixel 2 XL is the same older model that requires unlocking of the critical_partition, lock the critical_partitions again:

fastboot flashing lock_critical

Post installation precautions

OEM unlocking should be disabled again in the developer settings menu within the operating system. This prevents unlocking the bootloader without access to the owner account. CopperheadOS prevents bypassing the OEM unlocking toggle by wiping the data partition from the hidden recovery menu, unlike stock Android. You can still trigger factory resets from within the OS. Note that this means that recovering a device with a forgotten password is not possible without Copperhead doing it, which is the main purpose of this feature (anti-theft). Stock Android can be more forgiving because it's tied to a Google account.

Note: Unlocking the bootloader again will perform a factory reset. Do not plan to do so unless otherwise requried.

You should now disable OEM unlocking and factory reset the CopperheadOS device for optimal hardware security.

CopperheadOS Signing Key Verification

On device boot the device screen will show an OS fingerprint which is used by Android Verified Boot to match the signing keys of the Operating System installed. Comparing the fingerprint on boot to the keys below is a foolproof way to determine if the device has a verified CopperheadOS install. If the fingerprints below do not match the device boot screen there is a possibility it is a non-CopperheadOS install. If that is the case proceed with caution if the device was not purchased from an authorized CopperheadOS partner.

Sunfish (4a)5E1F9C66
Coral (4XL)66B85D8A
Flame (4)E598592C
Sargo (3a)83D59B40
Crosshatch (3XL)61FDA12B
Blueline (3)61FDA12B
Bonito (3aXL)8FF501EB
Walleye (2)6D54301A
Taimen (2XL)FB7A5A93


Update client

See the section in the usage guide.


Updates can also be downloaded from Copperhead and installed via recovery with adb sideloading. The zip files are signed and will be verified by the CopperheadOS recovery image. Sideloading should only be done if OTA updates are not working and there is a critical issue with Updater.

First, boot into recovery. You can do this either by using adb reboot recovery from the operating system or selecting the Recovery option in the bootloader menu.

You should see an Android lying on their back being repaired, with the text "No command" meaning that no command has been passed to recovery.

Next, access the recovery menu by holding down the power button and pressing the volume up button a single time. This key combination toggles between the GUI and text-based mode with the menu and log output.

Finally, select the "Apply update from ADB" option in the recovery menu and sideload the update with adb:

adb sideload $DEVICE-ota_update-$

Clearing custom AVB key

On the Pixel 2 and Pixel 2 XL, reverting back to stock requires clearing the configured public key after unlocking the bootloader and before locking it again with the stock factory images:

fastboot erase avb_custom_key

To confirm that the key is unset, verify that avb_user_settable_key_set is no:

fastboot getvar avb_user_settable_key_set