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The Windows Boot Manager (BOOTMGR) is the bootloader provided by Microsoft for Windows NT versions starting with Windows Vista and Windows Server 2008.It is the first program launched by the BIOS or UEFI of the computer and is responsible for loading the rest of Windows. [1]
If a UEFI Option ROM is not available, the system will revert to the legacy Option ROM. UEFI systems can utilize legacy Option ROMs through the Compatibility Support Module (CSM). When Secure Boot is enabled, the execution of CSM and legacy Option ROMs is prohibited as legacy firmware drivers do not support authentication, which creates a ...
UEFI requires the firmware and operating system loader (or kernel) to be size-matched; that is, a 64-bit UEFI firmware implementation can load only a 64-bit operating system (OS) boot loader or kernel (unless the CSM-based legacy boot is used) and the same applies to 32-bit.
The first stage of PC boot loaders (FSBL, first-stage boot loader) located on fixed disks and removable drives must fit into the first 446 bytes of the master boot record in order to leave room for the default 64-byte partition table with four partition entries and the two-byte boot signature, which the BIOS requires for a proper boot loader ...
GRUB 2, elilo and systemd-boot serve as conventional, full-fledged standalone UEFI boot managers (a.k.a. bootloader managers) for Linux. Once loaded by a UEFI firmware, they can access and boot kernel images from all devices, partitions and file systems they support, without being limited to the EFI system partition.
Once all the boot and system drivers have been loaded, the kernel starts the session manager (smss.exe), which begins the login process. After the user has successfully logged into the machine, winlogon applies User and Computer Group Policy setting and runs startup programs declared in the Windows Registry and in "Startup" folders.
If UEFI Secure Boot is supported, a "shim" or "Preloader" is often booted by the UEFI before the bootloader or EFI-stub-bearing kernel. [11] Even if UEFI Secure Boot is disabled this may be present and booted in case it is later enabled. It merely acts to add an extra signing key database providing keys for signature verification of subsequent ...
rEFInd is a boot manager for UEFI and EFI-based machines. [2] [3] It can be used to boot multiple operating systems that are installed on a single non-volatile device. It also provides a way to launch UEFI applications. [4] [5] It was forked from discontinued rEFIt in 2012, with 0.2.0 as its first release. [6] [7]