On the phone, select Settings -> About Phone. Locate the option called Build number and press on it 7 times in succession. You will then find that Developer Options is enabled in the About Phone menu.
First enable Developer Options. On the phone, select Settings -> About Phones -> Developer Options. Locate an option named Android debugging and change the toggle to On. The phone will now be in USB Debugging mode.
If you create a Linux Virtual Machine using VirtualBox, then you will find that when an Android Phone is connected to the computer via USB port, it will not be detected in the Linux virtual machine. To overcome this, in VirtualBox select Machine->Settings->USB and check Enable USB Controller and also check Enable USB 2.0 (EHCI) … Continue reading Phone not detected with adb in the VirtualBox Ubuntu guest