This is not just a competition to see how many acronyms we can fit into a chapter heading, although, out of four words, having used two already is not a bad start. The GRUB is the system-supplied bootloader that ships with CentOS and Red Hat Enterprise Linux 6. This tiny piece of bootstrap code is used to load the kernel and allows us to dual boot different Linux versions or even with Microsoft Windows operating systems. The GRUB has been the bootloader of choice for many years, although other bootloaders do exist. These include:
EXTLinux: This is part of the SYSLinux family that includes the following:
EXTLinux to boot from fixed drives
ISOLinux to boot from CDs and DVDs
SYSLinux to boot from a USB device
PXELinux to boot from the network
GRUB2: More recently, this is making its appearance as a replacement to GRUB, or what is now referred to as the legacy GRUB. GRUB2 is likely to debut in CentOS 7 in 2014.