Linux Fundementals

Question 1

When was linux released ?

Answer 1

1991

Question 2

To output simple text we use ?

Answer 2

Echo

Question 3

To check name of machine we use ?

Answer 3

whoami

Question 4

Command to find a file on linux ?

Answer 4

find -name file_name
find -name *.format_type

Question 5

What shell operators are there ? And what does each do ?

Answer 5

1. & - run cmd in the background, can also use CTRL + Z for scripts.
2. && - combine multiple commands
3. >
   • redirect output
4. > >
   • redirect output without overwriting

Question 6

Commands that we use regularly ?

Answer 6

Touch - create file
mkdir - create folder
cp - copy
mv - move
rm - remove
file - determine type

Question 7

How do we check what permissions files in a directory have ?

Answer 7

ls -l

Question 8

Switching to another user in linux command ?

Answer 8

su username
su -l username

Question 9

What are the 4 common directories ? What do they do ?

Answer 9

/etc - stores system files that OS uses, also stores “shadow” and “passwd” which has password storing method in sha512 encryption.
/var - accessed by running apps and services, has /var/log that stores variable data about these apps and services
/root - home directory of the root user
/tmp - like ram, stores data until shudown

Question 10

How to download files from a website ? via what ?

Answer 10

wget via HTTP

Question 11

Securely trasnfering files via SSH protocol command ? Syntax for sending and receiving to and from a remote server ?

Answer 11

scp - secure copy

scp file_name remote_user_name@remote_ip:path - to send

scp remote_user@remote_ip:path_to_file

Question 12

What command opens a running server via python ?

Answer 12

python3 -m http.server - to serve files

Question 13

Command to get from a server after python server deployment ?

Answer 13

wget http://machine_ip:port/file_name

Question 14

What are processes, what are they managed by ? How do they identify ?

Answer 14

Processes are programs ran on machine, managed by the kernel. They identify by their PID’s, and incremented in order i.e 60th process’s PID = 60

Question 15

How do we check the list of processes ?

Answer 15

ps command

Question 16

Command to check which user is running what process and processes that don’t run in that session ?

Answer 16

ps aux

Question 17

what does the top command do ?

Answer 17

gives real time stats of processes

Question 18

what does ps command do ? what does ps aux command do ?

Answer 18

ps command shows the processes ran in the session. ps aux shows users that run them and also processes not ran in the session

Question 19

How do we eliminate a process ?

Answer 19

kill “PID”

Question 20

what are other commands like kill what do they do ?

Answer 20

sigterm - kill the process but do cleanup beforehand
sigkill - kill without cleanup
sigstop - stop suspend a process

Question 21

What is the method of splitting resources up for specific processes called ? what is it good for and what is it’s specificity ?

Answer 21

Method is called namespaces, it is good for security since only the processes assigned the same resource (cpu, ram,etc..) can see each other.

Question 22

What is the first process when booting linux ?

Answer 22

systemd

Question 23

how do we communicate with systemd ?

Answer 23

systemctl [option] [service]
options : start, stop, enable, disable.

Question 24

What are the two states that processes can run in ? Give an example for both.

Answer 24

Foreground and background
If we take command “echo”
echo “hi” -> returns hi
if we do
echo “hi” & -> returns the ID for echo

Question 25

How do you foreground a process ?

Answer 25

fg

Question 26

How do we communicate with cron ? what is cron ?

Answer 26

crontabs. Cron helps us manage at what time a certain process will be deployed.

Question 27

What values does cron take ?

Answer 27

min - what minute to exec at
hour - what hour to exec at
DOM - what day of the month to exec at
MON - what month of the year to exec at
DOW - what day of the week to exec at
CMD - actual command that will be executed

Question 28

What is the syntax of the crontabs ? Helpful syntax ?

Answer 28

min hour DOM MON DOW CMD
Useful syntax : “/n” every n’th example : 0 */12 every 12’th hour.

Question 29

how do you edit crontabs ?

Answer 29

crontab -e

Question 30

Where do devs submit their software ?

Answer 30

to an apt repo