The recovery image is stored on the recovery partition and consists of a Linux image with a simple user interface controlled by hardware buttons. Recovery mode can be accessed in two ways:
- By pressing a certain keypress combination when booting the device (usually by holding the Volume+, Volume-, and Power buttons during the boot up)
- By issuing the adb reboot recovery command to a booted Android system
The following is a screenshot of a stock recovery mode on an Android device:
Android stock recovery
The stock Android recovery is intentionally very limited in functionality. It has the options to reboot the system, apply updates from ADB and SD card, factory reset, and so on. However, custom recovery offers many more options.