Several boot loaders are used on Linux systems, such as the Grand Unified bootloader (GRUB) and theLinux Loader (LILO). ESX uses LILO as the boot loader and has system components that expect the presence of LILO as the boot loader, so don't replace LILO with another boot loader, or your server may experience problems. The configuration parameters for the bootloader are contained in /etc/lilo.conf in a human-readable format, but the actual bootloader is stored in a binary format on the boot sector of the default boot disk. This section explains the boot process of ESX Server, as well as how to load the VMkernel and configuration files.

High-Level Boot Process for ESX Server

1. BIOS is executed on the server.

2. BIOS launches LILO from the default boot drive.

3. LILO loads Linux Kernel for the Service Console.

4. The Service Console launches VMkernel.

5. MUI Server is started.

6. Virtual machines can then be launched by VMkernel and managed through MUI.

Brief Notes:

LILO - LILO stands for Linux boot loader. It will load the MBR, master boot record, into the memory, which tell the system which partition and hard drive to boot.

Grub - GRUB stands for GRand Unified Bootloader. It is a multiboot loader that can deal with many types of hardware and knows how to load a wide variety of UNIX-based operating systems as well as Windows.

MBR - A master boot record (MBR), or partition sector, is the 512-byte boot sector that is the first sector ("LBA Sector 0") of a partitioned data storage device such as a hard disk. (The boot sector of a non-partitioned device is a Volume Boot Record. These are usually different, although it is possible to create a record that acts as both; it is called a multi boot record.)

VMkernal -

VMkernel is a POSIX-like operating system developed by VMware. The VMkernel is the liaison between virtual machines (VMs) and the physical hardware that supports them. VMware calls VMkernel a microkernel because it runs on bare metal, directly on VMware ESX hosts. The VMkernal is responsible for allocating memory, scheduling CPUs and providing other hardware abstraction and operating system (OS) services.