Linux+ and LPIC-1 Exam 101

Linux+ and LPIC-1: System Administrator - Exam 101

GRUB2

Linux+ and LPIC-1 Exam 101

Differences Between MBR and GPT

MBR (Master Boot Record):• Traditionally supported only 26 total partitions (4 partitions, with one partition extended to 23 partitions)• Partition size limited to 2TB

GPT (GUID Partition Table):• Supports 128 partitions• Partition size up in the ZB (zettabyte) range• Needs UEFI (Unified Extensible Firmware Interface) to boot:

• Replacement for traditional BIOS, can act in legacy BIOS mode

• Requires a 64bit operating system

• Prevents unauthorized operating systems from booting on the system

Linux+ and LPIC-1 Exam 101

GRUB2 on GPT with UEFI

UEFIBIOS

MBR(first 512

bytes)

boot.img

Stage 1

GPTHeader

PartitionEntryArray

Stage 2

/boot/grub2

grubenvthemes

Stage 1.5

core.img

typicallyemptysectors

/boot/efi

vfator

FAT32

ESP

Linux+ and LPIC-1 Exam 101

GRUB2 Configuration Commands:

grub2-editenv list

view the default boot entry for the grub configuration file as written in /boot/grub/grubenv

grub2-mkconfig

creates (or updates) a /boot/grub2/grub.cfg file based on entries from the /etc/default/grub file

(On Debian systems, the ‘2’ is omitted from the command name. e.g. grub-mkconfig)

update-grub

command that can be used to update a GRUB2 configuration after changes to /etc/default/grub have been made, found on Debian based systems