EMZETT.Bootloader
In short: The bootloader is the small program that the firmware starts after the self-test and that then loads and starts the operating system kernel in memory.
In more detail: The firmware can read files only roughly and is not meant to load a whole operating system. So the bootloader takes over: it finds the kernel, loads it with startup parameters and hands over control.
In Depth
| System | Bootloader |
|---|---|
| Windows | Windows Boot Manager (bootmgfw.efi) and Winload (winload.efi) |
| Linux | GRUB, systemd-boot, rEFInd |
| macOS | boot.efi (iBoot on Apple Silicon) |
| Android | Manufacturer bootloader (often locked) |
- Several systems (dual boot): The bootloader shows a menu and starts the chosen system.
- Locations: With UEFI it lives as an
.efifile in the EFI system partition; with legacy in the MBR plus active partition. - Tasks: Load the kernel, provide the initial RAM disk, pass command-line parameters, offer recovery options, check signatures (Secure Boot).
- Problems: “Operating system not found”, “BOOTMGR is missing”, “No bootable device” point to damaged startup files, wrong boot order or a missing partition. Repair:
bootrec /fixmbr,bootrec /rebuildbcd(Windows),grub-install(Linux). - Security: A manipulated bootloader is a dangerous attack point (bootkits). Secure Boot and encryption (BitLocker) reduce the risk.
- Android/iOS: “Unlock bootloader” allows custom systems but wipes data and can affect warranty and banking apps.
See also: Boot process of a Windows 11 computer, EFI system partition and system partition, Boot files