101.2 Boot the system Flashcards
What does BIOS stand for?
Basic Input/Output System
What function does the BIOS have?
The BIOS on the motherboard checks on all of the hardware and input and output devices after a computer starts.
What does Grub stand for?
GRand Unified Bootloader
What is the name of the boot program (boot loader) in Linux?
The boot program is called GRUB
What does the GRUB do?
The GRUB will look for the section of the hard drive that contains the data needed to boot the operating system.
Who mounts the file system from the hard disk on a computer at start?
The Linux Kernel
What does the Linux Kernel load at computer start?
Initial RAM disk and the file system
What is the order of First initialization in a computer?
BIOS > GRUB > Linux Kernel > Initial RAM Disk > FS > Initial RAM Disk Removal
What does the Linux Kernel load at computer start?
Initial RAM disk and the file system
What are boot logs?
Boot logs are logs that are generated when the computer itself boots up.
Where do boot logs come from?
Boot logs are generated from the Kernel Ring Buffer
Are boot logs volatile? What does that mean?
Yes, they are typically volatile, meaning that once the computer reboots, these logs are gone.
Is dmesg legacy to pull up info from the Kernel Ring Buffer?
Yes, now in most modern distros, systemd has substituted init and it uses journalctl instead of dmesg.
Is dmesg legacy to pull up info from the Kernel Ring Buffer?
Yes, now in most modern distros, systemd has substituted init and it uses journalctl instead of dmesg.
What does journalctl log?
It logs every event that goes on within the computer, including the kernel messages.
What does journalctl mean?
Journal control
what does the dmesg command show?
The dmesg utility shows the Kernel Ring Buffer messages.
What would you usually look for in the messages (dmesg) in the Kernel Ring Buffer?
You will use the Kernel Ring Buffer to see if hardware is getting recognized by the Linux Kernel.
The version of a init that has been used in Linux Systems is based off of the system _________.
V init system (also known as Sys V init).
After the Linux kernel loads up and it brings in the initial RAM disk, it then seeks out an initialization system to hand over control of the computer. What is the first place the kernel looks at?
/sbin/init
What does /sbin/init read once started?
It reads the config settings in /etc/inittab
What does the init process read in the /etc/inittab file?
It reads which run level the system should be operating in.
What is a downside to the classic init system?
Services are started up one after the other
If a particular service is not yet ready, it could hang the system preventing other services from starting.
What are the 3 main locations where you would find a systemd unit file?
- default location : /usr/lib/systemd/system - where unit files are installed by packages
- /run/systemd/system
- /etc/systemd/system (if modification is needed)
What happens in stage 1 of the boot process?
BIOS passes and it locates a bootloader (boot.img)
What happens in stage 1.5 of the boot process?
core.img file is located by the boot.img file
What is the version of GRUB that can be found in older systems?
Legacy GRUB
Inside the grub shell environment, what command do you use to find out the location of the stage 1 file?
> find /grub/stage1
what happens in stage 2 of the boot process?
The actual boot partition gets read.
What does MBR stand for?
Master Boot Record
How many partitions does MBR support?
24 (4 partitions with one extended to 23 partitions).
What was the largest partition size old MBR allowed?
2TB max.
What does UEFI stand for?
Unified Extensible Firmware Interface
What does UEFI replace?
The old BIOS
What type of architecture does UEFI need to work?
64bit OS
What comes after the MBR to let the system know it is a GPT style disk?
Using a GPT Header and the Partition Entry Array
What does the core.img in GRUB2 look for?
/boot/efi partition
What format does the /boot/efi partition (ESP EFI system partition) have to have?
vfat or FAT32
In GRUB2, what are the 2 files in stage 2 that are under /boot/grub2 ?
grubenv and themes
What is the command to view the default boot entry for the grub configuration file?
grub2-editenv list
Which command re-reads and updates the file /boot/grub2/grub.conf ?
grub2-mkconfig
In GRUB legacy, what key do you use to append or add options to the kernel boot line?
Letter A (A for append)
Once inside the GRUB legacy, what key do you use to open the GRUB command line?
The C key (C for CLI)
In GRUB2, what key do you use to edit a grub menu item?
The E key (E for Edit)
In GRUB2, what keys do you use to boot a selection or modified kernel parameter?
Ctrl+x or F10
In GRUB2, what is the line called that modifies the kernel?
Linux
What is the command you would use to see kernel messages in a Linux distro that uses systemd?
journalctl -k
What does the boot loader GRUB do?
The boot loader loads the Linux Kernel
To what pseudo file system does d-bus send the info to about a piece of hardware that is connected to the computer?
The info is attached to the /dev pseudo file system.
