101.2 Boot the system Flashcards
Describe the boot process for Boot of a linux system
BIOS - Boot Sector - Linux kernel - Initial - initialization
What are Boot logs
Logs created when the computer is booted up
What is the dmesg command
The traditional utility used for viewing the kernel ring buffer
What is journalctl -k
systemd utility to view the kernel ring buffer within the systemd journal
What is the kernel ring buffer
an area of RAM the kernel writes the system message to
Describe the init system startup
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
What is a runlevel
Predefined conifg that the computer will operate within, computer can only operate at one runlevel at a time
Describe runlevel 0 purpose
Halt - Computer stop services and halts the system
Describe the purpose of runlevel 1
Single user-mode - Root user only one allowed to login, only for repair, maintenance
Describe the purpose of runlevel 3
Multiuser mode (no networking) - allows multi users to login but with no networking
Describe the purpose of runlevel 4
Unused - there for if the user wants to setup a custom level environment
Describe the purpose of runlevel 5
Multi-user, with networking and a graphical desktop
Describe the purpose runlevel 6
Reboot
Describe the parts of a file in the /etc/initab
EX. id3initdefault;
:::
identifier- initdefault
runlevel - 3
action - initdefault - after the system boot it will run the runlevel mode chosen
Where on rehat distros are the scripts that init will use to start the system
/etc/rc.d/
Where on debian distros are the scripts that init will use to start the system
/etc/init.d
what does the command rc.local store
customized by sys add to starup services that dont have their own init files
What is stored inside the /etc/init/d/ file
scripts for the services on the system
What is stored inside the /etc/init.d/rc file
script that orchestrate how the runlevel scripts run and what occurs when a runlevel changes
What is an event?
A change on a linux system
What is a job
Task and services
Where are unit files stored at
/usr/lib/systemd/system
Where can an admin modify unit files
in the /etc/systemd/system
What is a unit file?
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
Where is the runtime unit files located
/run/systemd/system
What command allows you to view all of your systems files?
systemctl list-unit-files
How does the systemd boot the system
The kernel looks for /sbin/init
starts systemd
Explain the linux boot process (Simplified)
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
