Bootloader
A bootloader is
a computer program that loads an operating system (OS) or runtime environment
for the computer after completion of the self-tests.
The
bootloader configures the device to an initial known state and has a means to
select where to start executing the kernel. It can allow you to make this
selection, which give you for example the opportunity to start an alternative
Linux kernel, or Windows. Because the bootloader is an essential component of
the boot process, it is stored in non-volatile memory, such as flash memory.
Bootloaders
are written by hardware vendors and are specialized for the hardware they run
on.
For
Android devices, the bootloader typically starts either Android or Recovery.
Android bootloaders often have a basic interactive mode that can be triggered
by holding the "volume down" button while the bootloader is
executing.
Locked/unlocked bootloaders
A
locked bootloader is one that will only boot an OS that it "approves"
of. This may mean that device's boot partition has an approved digital
signature, or the carrier ID (CID) hard-coded into the OS matches a value
hard-coded into the bootloader itself. See also Wikipedia:Hardware
restrictions#Verified/trusted/secure boot and Wikipedia:SIM lock.
For
devices with a locked bootloader, booting an unsanctioned OS (e.g. CyanogenMod
or Ubuntu) requires the device's owner to first unlock (or even replace[1]) the
bootloader. Unlocking the bootloader sometimes voids the device's warranty.
Procedures vary typically by manufacturer.
Bootloader
unlocking should not be confused with Android rooting.
No comments:
Post a Comment