20250412

Question 1

A simple command that lists users who are logged into a Linux server

Answer 1

who

Question 2

What is | in Linux?
who | wc -l

Answer 2

it is pipe, a command that connects the output of who to the input of wc
The result is the number of lines in the output of who

Question 3

What does cd command do if you don’t provide it with any argments?

Answer 3

Returns you to your home directory like:
/home/smith
The same as echo $HOME or echo ~cd

Question 4

How to quickly go to somebody else’s home directory if you know there username? Like the username is Fred

Answer 4

cd ~fred

Question 5

What are the three parts of system directories in linux and how is it in this directory:
usr/local/share/emacs

Answer 5

• Scope usr/local - The purpose of the entire directory
• Category share - The type of the files found in directory like lib or bin
• Application emacs

Question 6

What are /, /usr, and /usr/local purposes?

Answer 6

/ system files supplied with you distribution (considered lower level)
/usr more system file supplied with you distro
/usr/local system files that are not supplied with your distro - They may be unique to your local Linux distro or your individual computer

Question 7

Name some category parts in Linux file systems and explain if necessary

Answer 7

• bin binary files - executable programs
• sbin programs for superusers
• doc
• info
• man
• etc Configuration files for the system
• init.d Configuration files for booting Linux
• src
• cgi-bin
• html
• public_html
• dev Device file for interfacing with disks and other hardware
• media, mnt, var, lock, log, mail, run, spool, tmp

Question 8

What is systemd and where it is located?

Answer 8

It is an aplication that is a service for configuring Linux machines - systemd contains configuration files for that service

Question 9

Name some kernel-related directories

Answer 9

• /boot - files for booting the system - the kernel lives here, typycally in /boot/vmlinuz or a file of a similar name
• /lost+found - Damaged files that are rescued by a disk recovery tool (permission denied!)
• /proc files for currently running processes - for advanced users
• /sys files for kernel internals

Question 10

What is -d option in ls command of linux

Answer 10

The -d option in the ls command stands for “directory”, and it changes the behavior of ls so that it shows information about the directory itself, rather than listing the contents inside the directory.

Question 11

How to know which shell you are running?

Answer 11

echo $SHELL

Question 12

To print a command’s (like find) location in your search path:

Answer 12

type find
which find

Question 13

To add directories to your shell’s search path temporarily

Answer 13

You can append usr/sbin to your search path:
- PATH=$PATH:/usr/sbin

Question 14

How to determine whether a command is in the filesystem, a built-in command, or an alias?

Answer 14

use the type command
- type wc cd