Install /e/OS on a Teracube Teracube 2e (2021) - “emerald”

The instructions in this guide will assist you to install /e/OS on your emerald. Please read through the instructions at least once before actually following them, so as to avoid any problems later.

It is important that you know that downgrading Smartphones on OS versions greater than the /e/OS OS version you plan to install, can cause instability or at worst brick some devices. We recommend that you check your current OS version, before attempting the installation.

It is advisable to flash your device only if you know what you are doing and are ok taking the associated risk. All /e/OS builds are provided as best effort, without any guarantee. The /e/OS project and its project members deny any and all responsibility about the consequences of using /e/OS software and or /e/OS services.


  • If required take a backup of all important data from your phone on an external storage device before proceeding.
  • Do not take a backup on the same device as some of these actions will format the device and delete the backup.
  • Ensure your phone is charged more than 50%
  • Check that adb and fastboot are enabled on your PC. If not you can find the setup instructions here
  • Download all the files and images mentioned in the download section below before starting the installation
  • Make sure you have a working data cable to connect your device to the PC. There are cables which are only for charging and do not transfer data.

  • Enable USB debugging on your device. You can find the instructions here
  • Make sure that your model is listed in the Smartphone Selector. Check the model supported. Where available, information on the model supported should show as a pop-up when you hover the cursor on the Device name. The model number supported should be the exact same.
  • Boot your device with the stock OS at least once and check every functionality.
Warning: Make sure that you can send and receive SMS and place and receive calls (also via WiFi and LTE, if available), otherwise it will not work on /e/OS as well. Additionally, some devices require that VoLTE/VoWiFi be utilized once on stock to provision IMS.

Please share your experience , suggest tips or changes to this install guide documentation by visiting the Teracube 2e (2021) specific topic on our community forum.

To report issues in /e/OS please refer this guide

Caution: Before moving forward, ensure your device is a Teracube 2e (2021). Please look at the serial number under the battery or dial *#06#. If the serial number starts with 2021 (ex: 202111T2Exxxxxx), you are at the right place! If it starts with 2020, please move to Teracube 2e (2020) documentation

Downloads for emerald

To understand the difference between /e/OS builds check this guide

Warning: Please note some of the above links can lead to external sites

Unlock the bootloader

Caution: Please take a backup of your data as unlocking the bootloader will reset your device to factory defaults.
  1. Enable USB debugging and Allow OEM Unlock following the guide given here
  2. Reboot in fastboot.

  3. You can follow either of two methods (Automatic or Manual) to continue. We give details of both the methods below. Only one needs to be selected

    • Automatic
      • From your computer, run

        adb reboot bootloader

    • Manual
      • Turn off your phone and start it with power + volume up keys.
  4. The menu will present three options, press volume up until Bootloader is selected. Press volume down to accept this choice.

OEM unlock the device

  1. Once your phone is in fastboot mode, on your PC type in a console the below command

    fastboot flashing unlock

  2. Press volume up on your phone to accept.
  3. The device will reboot automatically after an unlock.

Installing /e/OS from the bootloader

  1. Download the build package linked in the Downloads section above and extract it to a folder of your choice
  2. Connect the device to your PC if not already done

    Ensure you have a cable which allowed file transfer. Some cables can only be used for charging.

  3. Move to the directory where you have extracted the files in the first step. To do that type the below command in a console
    cd path-of-the-extracted-files
  4. Install /e/OS by typing the following commands in the console
fastboot erase userdata
fastboot format md_udc

fastboot flash boot_a boot.img
fastboot flash dtbo_a dtbo.img
fastboot flash vbmeta_a vbmeta.img
fastboot flash vbmeta_system_a vbmeta_system.img
fastboot flash vbmeta_vendor_a vbmeta_vendor.img
fastboot flash super super.img
fastboot flash lk_a lk.img
fastboot flash logo logo.bin
fastboot flash preloader_a preloader_emerald.bin
fastboot flash tee_a tee.img
fastboot flash gz_a gz.img
fastboot flash sspm_a sspm.img
fastboot flash scp_a scp.img
fastboot flash spmfw_a spmfw.img
fastboot flash md1img_a md1img.img

fastboot --set-active=a
fastboot reboot
Tip: If your device is not detect by fastboot, try to use sudo fastboot instead

Locking the Bootloader

Once you have completed the above steps and before rebooting you can lock your Bootloader.

  1. Boot your device into bootloader if not already there, and plug it to your computer
  2. Lock the device with the following command
    • fastboot flashing lock
    • Approve with Volume up
  3. Reboot with fastboot reboot
Success: Congratulations !! Your phone should now be booting into /e/OS !!
To find some troubleshooting tips… click here


  • Getting a Total xFer ':' 0.01x message - Try to upload the /e/OS to internal storage and retry to install
  • adb ':' sideload connection failed ':' insufficient permissions for device error - Try to execute the commands adb kill-server and adb start-server and retry
  • Running adb shell twrp install /sdcard/</e/OS zip package> raise non-existent directory error - Try to check solution here
  • Getting an insufficient permissions error - Try the solution given here
  • When running "adb devices" in bash a device is shown as "unauthorized" - Try the solution given here


  • Errors while running TWRP version 3.4.x.x or above - Try downloading and using a previous TWRP version.. below 3.4.x.x
  • In TWRP if this error shows up failed to mount /preload - Try in TWRP wipe screen in advanced menu select preload and swipe to wipe
  • /cache/recovery/xxx -> no such file or directory error while flashing a ROM - On PC run adb shell in the console now create a folder called recovery for e.g. here the devicecode name is violet "violet :/cache# mkdir recovery"


  • Trying to troubleshoot mobile connectivity issues - Read this guide

Please share your experience , suggest tips or changes to this install guide documentation by visiting the Teracube 2e (2021) specific topic on our community forum.

To report issues in /e/OS please refer this guide