Linux Basics for Beginners: Essential Commands and Examples

1. User Management

Managing users is crucial in any Linux system, whether for security or resource allocation.

Create a User

Use the useradd command to create a new user.

sudo useradd newuser
sudo passwd newuser

Delete a User

Remove a user and their home directory with:

sudo userdel -r newuser

---

2. Group Management

Groups allow better access control and management of multiple users.

Create a Group

Use the groupadd command to create a new group.

sudo groupadd developers

Delete a Group

Remove a group using:

sudo groupdel developers

Add a User to a Group

sudo usermod -a developers newuser

---

3. File and Directory Management

Files and directories are the building blocks of Linux. Knowing how to create and manage them is essential.

Create a File

Use touch to create a blank file:

touch file.txt

Create a Directory

Create a new directory using mkdir:

mkdir my_directory

Delete a File

Remove a file with:

rm file.txt

Delete a Directory

Use rmdir to remove an empty directory or rm -r for directories with contents:

rmdir my_directory
rm -r my_directory

---

4. Searching with grep and awk

Using grep

grep searches for patterns in files:

grep "pattern" file.txt

Example: Find all lines containing "error" in a log file:

grep "error" /var/log/syslog

Using awk

awk is a text-processing tool:

awk '/pattern/ { print $0 }' file.txt

Example: Print the second column of a file:

awk '{ print $2 }' file.txt

---

5. File Permissions Management

File permissions determine who can read, write, or execute a file.

View File Permissions

Use ls -l to see permissions:

ls -l file.txt

Change Permissions

Use chmod to modify permissions:

chmod 755 file.txt

Change Ownership

Change the owner or group of a file:

sudo chown user:group file.txt

---

6. SSH and SCP for Remote Connections

SSH (Secure Shell)

SSH lets you connect securely to a remote server:

ssh -i "example.pem" user@remote_server_ip

SCP (Secure Copy)

Copy files securely between local and remote systems:

scp -i "example.pem" file.txt user@remote_server_ip:/path/to/destination

---

Sample Workflow

Here’s a sample use case combining these commands:

1. Create a user and assign them to a group:

    sudo useradd john
    sudo passwd john
    sudo groupadd engineers
    sudo usermod -a engineers john
   

2. Create a file and set permissions:

    touch project.txt
    chmod 644 project.txt
    sudo chown john:engineers project.txt
   

3. Search a file for errors using grep:

    grep "error" /var/log/syslog
   

4. Transfer the file to a remote server:

    scp project.txt john@192.168.1.100:/home/john/
   

   Thank you for reading :)

   Ramya R