Enjoy your Linux journey! 😊🐧✨

Don't be intimidated by the terminal; mastering Linux commands can be an enjoyable and empowering experience! 🤓

To view what's written in a file.
```
 cat file.txt
```

To change the access permissions of files.

 chmod 777 file.txt #owner-group-other has read-write-execute permission

To check which commands you have run till now.
```
 history
```

To remove a directory/ Folder.

 rm -rf file.txt
 rmdir -rf /folder/myfolder

To create a fruits.txt file and to view the content.
```
 vim fruits.txt #create a file
```

Add content in devops.txt (One in each line) - Apple, Mango, Banana, Cherry, Kiwi, Orange, Guava.

 # After creating file using vim, type 'i' to insert content as - Apple, Mango, Banana, Cherry, Kiwi, Orange, Guava
 #save it by ':wq!' 
 cat fruits.txt #see the content of the file

To Show only top three fruits from the file.
```
 head -3 fruits.txt
```
To Show only bottom three fruits from the file.
```
 tail -3 fruits.txt
```
To create another file Colors.txt and to view the content.
```
 touch colours.txt
 cat colours.txt
```

Add content in Colors.txt (One in each line) - Red, Pink, White, Black, Blue, Orange, Purple, Grey.

vim colours.txt # Red, Pink, White, Black, Blue, Orange, Purple, Grey.
                                #OR
echo "Red" >> Colors.txt
echo "Pink" >> Colors.txt

To find the difference between fruits.txt and Colors.txt file.
```
diff <fruits.txt> <Colors.txt>
```

Write a Shell Script to take user input, input from arguments and print the variables.

########### WRITE A SIMPLE CODE TO TAKE INPUT FROM THE USER & PRINT ##########
#!/bin/bash
echo "Hello, who am I talking to?" # Ask the user for their name
read varname
echo "It is nice to meet you $varname"

Write an Example of If else in Shell Scripting by comparing 2 numbers

#!/bin/bash
echo "Enter a number:"
read num

if [ $num -gt 0 ]; then
    echo "It's a positive number!"
elif [ $num -lt 0 ]; then
    echo "It's a negative number!"
else
    echo "It's zero!"
fi

Create 90 directories (day1 .. day 90)within seconds using a simple command
```
mkdir day{1..90}
```
Write a bash script createDirectories.sh that when the script is executed with three given arguments (one is directory name and second is start number of directories and third is the end number of directories ) it creates specified number of directories with a dynamic directory name.
```
# $1-Day(Directory Name) $2-StartDay $3-EndDay
#!/bin/bash
start_day=$2
end_day=$3
for (i=start_day;i<=end_day;i++)
do
mkdir $1$i
done
```
Execute as ./createDirectories.sh day 1 90

if we run like ./createDirectories.sh Movie 20 50 then it creates 50 directories as Movie20 Movie21 Movie23 ...Movie50

Create a Script to backup all your work done till now. backup.sh

#!/bin/bash
src_dir=/home/ubuntu/myprofile/scripts/*.sh
target_dir=/home/ubuntu/backup

current_time=$(date +"%Y-%m-%d-%H:%M")
backup_file=$target_dir/$current_time.tgz

echo "Started Backup for $src_dir"
tar -czf $backup_file --absolute-names $src_dir
echo "Backup Completed!"

Automate the backup Script - Visit https://crontab.guru/

* 2 0 * * /root/backup.sh #first of every month at 2 am.

Create 2 users and just display their Usernames

sudo useradd user1
sudo useradd user2
cat /etc/passwd

Create a simple file and see the details of the files

touch file1.txt
ls #see the files 
ls -a # -a show hidden files as well

Change the owner of a file from ubuntu to kshitija

sudo chown kshitija file.txt #Now owner of file.txt is kshitija
ls -ltr

Modify file permission
```
sudo chmod 755 file.txt
ls -ltr
```

ACL commands getfacl and setfacl

getfacl <file or directory name>
#To add permission for user -m : modify
setfacl -m u:kshitija:rwx test/declarations.h
#To add permissions for a group
setfacl -m "g:group:permissions" /path/to/file
#To remove ACL permission of user: -x = remove
setfacl -x "u:user:permissions" /path/to/file
#To remove ACL permission of group:
setfacl -x "g:group:permissions" /path/to/file

You have to install docker and jenkins in your system from your terminal using package managers

#!/bin/bash

#Docker Installetion
sudo apt update 
sudo apt  install docker.io -y
sudo apt install docker-compose -y

#Jenkins Installetion 
#for jenkins firstly you need java so 
sudo apt update
sudo apt install openjdk-11-jre -y

#Jenkins
curl -fsSL https://pkg.jenkins.io/debian-stable/jenkins.io-2023.key | sudo tee \
  /usr/share/keyrings/jenkins-keyring.asc > /dev/null
echo deb [signed-by=/usr/share/keyrings/jenkins-keyring.asc] \
  https://pkg.jenkins.io/debian-stable binary/ | sudo tee \
  /etc/apt/sources.list.d/jenkins.list > /dev/null
sudo apt-get update
sudo apt-get install jenkins -y

#for start jenkins
sudo systemctl start jenkins
sudo systemctl enable jenkins

📂 File and Directory Management

ls: List files and directories in the current location.
cd: Change the current directory.
pwd: Print the working directory – know where you are!
mkdir: Create a new directory.
touch: Create a new file.
cp: Copy files or directories.
mv: Move or rename files or directories.
rm: Remove files or directories (be cautious with this one! 😅).

🌐 Networking Magic

ping: Check network connectivity to a specific server or IP address.
ifconfig: Display network interface configuration (older command; use ip command on newer systems).
ssh: Securely connect to a remote server.
wget: Download files from the web directly in the terminal.

🔧 System Configuration

sudo: Execute a command with superuser (root) privileges.
top: Monitor system processes and resource usage.
apt: Advanced Package Tool - install, update, or remove software packages (Debian-based systems).
yum: Install, update, or remove software packages (Red Hat-based systems).

🛡️ Security

passwd: Change your user password.
chmod: Change file permissions.
chown: Change file ownership.

📅 Date and Time

date: Display or set the system date and time.

🚮 Trash Talk

rm (with caution!): Move files to the trash instead of permanently deleting them. Use alias to set up a trash command.

🌟 Bonus Tips

Use man followed by a command to access the manual page and learn more about it (e.g., man ls).
Combine commands using pipes (|) to create powerful one-liners.

THANK YOU! :)