101.2 Boot the system

Question 1

Describe the boot process for Boot of a linux system

Answer 1

BIOS - Boot Sector - Linux kernel - Initial - initialization

Question 2

What are Boot logs

Answer 2

Logs created when the computer is booted up

Question 3

What is the dmesg command

Answer 3

The traditional utility used for viewing the kernel ring buffer

Question 4

What is journalctl -k

Answer 4

systemd utility to view the kernel ring buffer within the systemd journal

Question 5

What is the kernel ring buffer

Answer 5

an area of RAM the kernel writes the system message to

Question 6

Describe the init system startup

Answer 6

after the kernel loads up the ram, it seeks out an initialization system to hand over control of the computer in folder /sbin/init
Then init reads the config file in the /etc/inittab

Question 7

What is a runlevel

Answer 7

Predefined conifg that the computer will operate within, computer can only operate at one runlevel at a time

Question 8

Describe runlevel 0 purpose

Answer 8

Halt - Computer stop services and halts the system

Question 9

Describe the purpose of runlevel 1

Answer 9

Single user-mode - Root user only one allowed to login, only for repair, maintenance

Question 10

Describe the purpose of runlevel 3

Answer 10

Multiuser mode (no networking) - allows multi users to login but with no networking

Question 11

Describe the purpose of runlevel 4

Answer 11

Unused - there for if the user wants to setup a custom level environment

Question 12

Describe the purpose of runlevel 5

Answer 12

Multi-user, with networking and a graphical desktop

Question 13

Describe the purpose runlevel 6

Answer 13

Reboot

Question 14

Describe the parts of a file in the /etc/initab

EX. id3initdefault;

Answer 14

:::
identifier- initdefault
runlevel - 3
action - initdefault - after the system boot it will run the runlevel mode chosen

Question 15

Where on rehat distros are the scripts that init will use to start the system

Answer 15

/etc/rc.d/

Question 16

Where on debian distros are the scripts that init will use to start the system

Answer 16

/etc/init.d

Question 17

what does the command rc.local store

Answer 17

customized by sys add to starup services that dont have their own init files

Question 18

What is stored inside the /etc/init/d/ file

Answer 18

scripts for the services on the system

Question 19

What is stored inside the /etc/init.d/rc file

Answer 19

script that orchestrate how the runlevel scripts run and what occurs when a runlevel changes

Question 20

What is an event?

Answer 20

A change on a linux system

Question 21

What is a job

Answer 21

Task and services

Question 22

Where are unit files stored at

Answer 22

/usr/lib/systemd/system

Question 23

Where can an admin modify unit files

Answer 23

in the /etc/systemd/system

Question 24

What is a unit file?

Answer 24

a plain text ini-style file that encodes information about a service, a socket, a device, a mount point, an automount point, a swap file or partition, a start-up target, a watched file system path, a timer controlled and supervised by systemd

Question 25

Where is the runtime unit files located

Answer 25

/run/systemd/system

Question 26

What command allows you to view all of your systems files?

Answer 26

systemctl list-unit-files

Question 27

How does the systemd boot the system

Answer 27

The kernel looks for /sbin/init

starts systemd

Question 28

Explain the linux boot process (Simplified)

Answer 28

BIOS -> Checks hardware of I/O of hardware
BootSector/GRUB -> Looks for the section of the hardrive that stores the data for the OS
Linux Kernel -> Kernel is loaded
Initial Ram disk -> The kernel loads the intial ram disk , loads the computers drivers to mount the filesystem from the disk
Initialization -> Takes over mounting the computer file systems, loads systems and gets computer ready to be used