Unix/Linux (Study)

mv

move

command mode

delete and change text

useradd

add a user

cat

catagontinate view a script file

Kernel (ring 0): kernel mode

The executing code has full, unrestricted access to the hardware

/bin

binary executables

groupadd

add a group

groupmod

modify a group

pwd

present working directory

passwd

password

default permissions for:

file:

directory:

File = 666

Directory = 777

uname

operating system

uname -srv

verbose operating (output)

tar -xvf

restore or obtain a backup

tar -cvf - create a backup from the beginning 3 layers

Application, Shell, kernel

Daemon

services that run in the background

Cron

daemon used to schedule jobs and tasks

Grub

most important software

/dev

device files and memory block

CLI

shell

ls -a

show hidden files

primary purpose of kernel

resource allocation

/sbin

administrative only available to root

/etc

critical directory

Check permissions

-ls -lisa

-ls -l

-ls -la

What mode do you need to be in to access applications

user mode

Full unrestricted access

kernel mode

6 reboot mode

All processes terminated; system is gracefully rebooted

2 multi-user mode

Allows users to access the system; limited network services

Post runs in

Bios

Place where everyone can execute local binary files

/usr/local/bin

Privileged tasks run in

kernel

Check consistency

fsck

# of permissions so everyone can execute

755 (lowest odd number)

crontab files located

/etc/.crontab

/etc/shadow

authentication

/etc/group

authorization

/etc/passwd

both authentication and authorization

-G

Supplementary/secondary group

tar

tape archive

/tmp

temporary files

Kernel mode

full unrestricted access and executing code

What happens in the Basic Input/Output (BIOS) phase?

Performs the Power on Self-Test (POST) and the master boot record (MBR) is executed.

How can the currently running shell can be determined?

echo $SHELL

Characters 2-4 (first set of permissions)

Owner permissions

Characters 5-7 (second set of permissions)

Group permissions

Characters 8-10 (third set of permissions)

Other permissions