How To Use ADB & Fastboot Commands Without A Computer But Using Another Smartphone [GUIDE]


Today we will see with this guide how to use the ADB and Fastboot commands without a computer, in order to be able to use these powerful tools we will need nothing more than two smartphones freeing you completely from the PC. With the use of smartphones and tablets, it is not uncommon to find homes where computers are no longer present, many use the phone only for browsing or for some games, so they have no need to have a PC at home. But things get complicated when there is to use the ADB and Fastboot tools, in this case, in fact, there was need of a computer to be able to use it, but as we will see in this guide, by now it will be enough to have a smartphone to run ADB and Fastboot and all its commands instead of the computer.

Before Android Marshmallow it was possible to execute the commands for ADB and Fastboot through the smartphone itself, but later this possibility was removed. However, thanks to the Magisk ADB and Fastboot module, it will be possible to enable this feature again on your Android device. With this guide you will see how to use the ADB and Fastboot commands without a computer but instead using a smartphone with which you can go to unlock the bootloader of other phones, with which you can install the TWRP and with which you can run the device Root via Magisk, all without the need for a PC.

To be able to use ADB and Fastboot commands without a computer you will need the following requirements:

  • The device that will have to take the place of the computer with already active Root permissions and USB OTG support
  • Magisk Manager installed on the device that you will need to use instead of the PC
  • USB data cable or alternatively an OTG adapter to connect the two Android smartphones together

The guide requires the device to be used instead of the computer with already active root permissions, otherwise, it will not be possible to proceed. You can then use an old phone with the Root permissions that you had already activated or you can borrow a phone with Root permissions unlocked by some of your friends. Alternatively, you could buy an Android smartphone for a few tens of euros, may be used, be used only for ADB and Fastboot commands.

Let’s see below all the steps necessary to be able to use ADB and Fastboot commands without a computer:

How to use ADB and Fastboot commands without a computer- install ADB and Fastboot for Android

From the smartphone with already active Root permissions, so to speak what you will have to use instead of the computer:

  • Access the Magisk Manager application and press the button on the left corresponding to the Menu
  • Then go to Download
  • Now press the search icon and search for “adb” to view the form that is needed to perform this guide ( ADB & Fastboot for Android NDK )
  • Tap the arrow to download the download and then press the Install button
  • At this point you will need to grant Magisk Manager the permissions to access your media files and if required you will need to click on Allow in order to start the installation
  • Now wait for the installation to complete, which should normally not take long
  • Once the module is installed proceed with the restart of the smartphone

How to use ADB and Fastboot commands without a computer- install the Termux application

Once the ADB module has been installed and the phone has been restarted, you will still have to use the smartphone with Root access to install a terminal application from which you can send ADB and Fastboot commands to the other device. Some smartphones already have an app that works as a terminal, but I also suggest for practical reasons in this guide to proceed with downloading the Termux application in order to proceed with sending commands.

How to use ADB and Fastboot commands without a computer- enable USB debugging

Now we have to switch to the second phone, the one to which you want to receive commands. In this case we need to enable USB Debugging from the Developer Options so the smartphone will be able to receive commands from the other telephone device just as if it were receiving them from a computer. Generally the procedure is similar for all Android devices and refers you to reading the guide on how to activate Developer Options on Android. Once the Developer Options are active, you will be able to access them and also enable USB Debugging.

How to use ADB and Fastboot commands without a computer- connect the two Android smartphones

If the two smartphones you have are of recent construction you could probably need only one USB Type-C cable to be able to connect them together. However, if you do not have a Type-C cable with the same connector on both ends, then you will need to use an OTG adapter. There are several smartphones that incorporate this adapter in their packaging, so before you buy one or ask for a loan from a friend of yours, check the smartphone box if you find one.

If one of the smartphones has a Micro USB socket and the other instead of Type-C, you will need instead of:

  • 1 x Micro USB OTG cable
  • 1 x USB to USB Type-C cable

If you need to use an OTG adapter, connect it to the smartphone on which you already have active Root and Termux permissions installed, then connect the USB cable to the other smartphone to which you will have to send the commands. If instead, you use a Type-C cable, it is not important which device you connect first as both smartphones make use of the same connector.

How to use ADB and Fastboot commands without a computer- allow USB Debug authorization

Once the two smartphones are connected to each other through the cable you have decided to use, you should display the message “Allow USB Debugging” on the phone without Root permissions, otherwise, if the warning message does not appear, disconnect the device and connect it again until you see the writing appear. Once you have shown the message with reference to USB Debugging, press on the option “Always allow from this computer“, then confirm everything by pressing OK. From this moment on you can use the phone on which you installed Termux to be able to send ADB and Fastboot commands, just like you would normally do from your computer.

If your secondary device is a Samsung (ie the one that should receive commands) of recent construction, you will probably have to change the “USB controlled by” option via the file transfer notification. The change must be made by switching from “Device connected” to “This phone, so once this is done you should see the USB debugging prompt.

If you then use devices with Type-C port and you don’t want one smartphone to download the other’s battery, using it in practice as an external battery, make sure to turn off the “Charge connected device” option. However, this only applies to smartphones with a Type-C type charging port.

How to use ADB and Fastboot commands without a computer- grant Root access

For this step you will need to use the smartphone where you have already installed Termux :

  • Access the Termux application, then type the command su followed by the Enter key. This will require Termux to acquire Root permissions via Magisk
  • Confirm the Superuser request by clicking on Grant (GRANT) in this way you will have access from now on to the Root
  • The command seen above you will have to run it every time you do something that requires Root access in a terminal, but after the first time, you no longer have to press Concede every time.

How to use ADB and Fastboot commands without a computer- check that the two smartphones communicate correctly with each other

Just like it normally happens when using ADB and Fastboot to connect a computer with the smartphone, even in this case where two smartphones are connected to each other, it will be necessary to test that they manage to communicate with each other without problems. Here’s how:

  • From the phone with Root permissions and on which you have installed Termux as a terminal app, open it and type the following adb devices command then press Enter and if the two smartphones are able to communicate with each other via ADB you should see a code on Termux composed of numbers and letters followed by “device” under the heading List of device attached (eg. 678KPOTRE2G device). So if you see a similar code it means that everything is going well and that the two smartphones are communicating correctly with each other
  • Try to see if the ADB and Fastboot commands work properly. Enter the adb reboot command to test the smartphone with Termux to restart the device to which the command was sent. If everything is working properly, you will now see the device reboot after it received the reboot order

Now that ADB and Fastboot are working properly and you can send commands from one smartphone to another instead of the computer, you can finally install all the types of mods you want on the phone, for example, you can proceed with the installation of the TWRP, run Root with Magisk, etc.. You can also use the smartphone instead of the computer to unlock for example the bootloader of a friend of yours directly to his home or why not also to the bar, in class at school, at work, without the need to bring an inconvenient and bulky computer.


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