- Embedded devices such as Android have a different bootloader, but for Desktop and Servers - GRUB is the main one.
- GRUB comes after POST and BIOS.
- Some part of GRUB will be available on the disk for the BIOS to find. The BIOS finds that and GRUB can load more of itself in.
- GRUB loads the Kernel, initla root filesystem into memory, sets up the Kernel command line and transfers control to the Kernel.
- The file it loads is VMLINUZ for the Kernel and the Initial Root Filesystem.
- The Initial Root Filesystem is a RAM disk image with
/etc and other basic directories. This helps load drivers, that the Kernel requires and can then continue to boot.
- GRUB knows what options to pass to the Kernel.
- GRUB can be interrupted before it starts Linux.
- Can change how it boots Linux and which Kernel it is going to boot. In addition, retrieving a Kernel over the network.
- GRUB has support for filesystems. GRUB can find files like Kernel files by name.
- Can search for a file and also do
file name completion (when pressing tab)
- More commands with
man -k grub and will list all commands with the keyword grub.