Linux Fundamentals Part 3

https://tryhackme.com/room/linux3

Task 1 Intro

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Task 2 [Section 5: Advanced File Operations] - cp

cp duplicates(copies) files. The syntax is cp <file> <destination>

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Task 3 [Section 5: Advanced file Operations] - cd && mkdir

Linux allows you to change the location of the current directory through the use of the cd command. The syntax of the cd command is this, cd <directory>.

This brings us to mkdir, occasionally you'll want to make a new directory to store files in, and that is done using mkdir, the syntax of mkdir is mkdir <directory name>.

Using relative paths, how would you cd to your home directory.

cd ~

Using absolute paths how would you make a directory called test in /tmp

mkdir /tmp/test

Task 4 [Section 5: Advanced File Operations] ln

The ln syntax is ln source destination.

The syntax for a symbolic link is the exact same, but it uses the -s flag, so to create a symbolic link, you would run ln -s <file> <destination>.

How would I link /home/test/testfile to /tmp/test

ln /home/test/testfile /tmp/test

Task 5 [Section 5 - Advanced File Operations]: find

The true power of this command though comes from the parameters you can provide it. You can use find dir -user , to list every file owned by a specific user; you can use find dir -group to list every file owned by a specific group.

How do you find files that have specific permissions?

-perm

How would you find all the files in /home

find /home

How would you find all the files owned by paradox on the whole system

find / -user paradox

Task 6 [Section 5: Advanced File Operations] - grep

grep <regular expression> <file>

What flag lists line numbers for every string found?

-n

How would I search for the string boop in the file aaaa in the directory /tmp

grep boop /tmp/aaaa

Task 7 Binary - Shiba3

What is shiba4's password

test1234

Task 8 [Section 6: Miscellaneous]: Intro

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Task 9 [Section 6: Miscellaneous]: sudo

sudo is Linux's run as administrator button, and the syntax goes sudo <command>.

How do you specify which user you want to run a command as.

-u

How would I run whoami as user jen?

sudo -u jen whoami

How do you list your current sudo privileges(what commands you can run, who you can run them as etc.)

-l

Task 10 [Section 6: Miscellaneous]: Adding users and groups

The syntax for both of these commands are adduser username and addgroup groupname.

How would I add the user test to the group test

sudo usermod -a -G test test

Task 11 [Section 6: Miscellaneous]: nano

nano is a terminal based text editor. The syntax for nano is nano <file you want to write to>

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Task 12 [Section 6: Miscellaneous]: Basic shell scripting

#!/bin/bash
echo hello
echo whoami
whoami

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Task 13 [Section 6: Miscellaneous]: Important Files and Directories

• /etc/passwd - Stores user information - Often used to see all the users on a system

• /etc/shadow - Has all the passwords of these users

• /tmp - Every file inside it gets deleted upon shutdown - used for temporary files

• /etc/sudoers - Used to control the sudo permissions of every user on the system

• /home - The directory where all your downloads, documents etc are.

• /root - The root user's home directory

• /usr - Where all your software is installed

• /bin and /sbin - Used for system critical files

• /var - The Linux miscellaneous directory, a myriad of processes store data in /var

• $PATH - Stores all the binaries you're able to run

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Task 14 [Section 6 - Miscellaneous]: Installing packages(apt)

apt install package

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Task 15 [Section 6: Miscellaneous]: Processes

A list of user created processes can be viewed with the ps command

To view a list of all system processes, you have to use the -ef flag

The syntax of kill is kill <PID>.

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