Security (2025 Edition)
📘 TABLE OF CONTENTS:
1. Introduction to System Administration
o What is System Administration?
o Roles and Responsibilities
o Types of Operating Systems
2. Linux Administration Basics
o Linux Directory Structure
o File Permissions & Ownership (chmod, chown)
o User & Group Management (useradd, passwd, groupadd)
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o Package Management (APT/YUM)
o Cron Jobs and Automation
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3. Windows Server Administration
o Active Directory Overview
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o Group Policy Management
o User/Computer Account Management
o Services and Task Scheduler
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o File Sharing and NTFS Permissions
4. Authentication and Access Control
o Role-Based Access Control (RBAC)
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o LDAP & Kerberos
o Multi-Factor Authentication (MFA)
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o Account Lockout Policies
5. Network Services & Configuration
o DNS, DHCP, FTP, and HTTP Services
o Configuring IP and Host Files
o Static vs Dynamic IPs
6. System Security Concepts
o Firewalls (UFW/Windows Firewall)
o Antivirus & Anti-Malware
o Patch Management
o Event Logging and Monitoring
7. Hardening Operating Systems
o Disable Unused Services
o Secure Boot and BIOS Settings
o File Integrity Monitoring
o Least Privilege Principle
, 8. Backup and Recovery
o Backup Strategies (Full, Incremental, Differential)
o Windows Backup Tools
o Linux Backup with rsync, tar, and cron
o Disaster Recovery Planning
9. Command-Line Essentials
o Linux Command Cheatsheet
o Windows PowerShell Essentials
o Common Admin Scripts
10. Practice Questions & MCQs
o 30+ Multiple Choice Questions
o Command-Based Questions
o True/False Concept Check
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1. Introduction to System Administration
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What is System Administration?
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System Administration is the practice of managing and maintaining computer systems,
networks, and servers to ensure they operate efficiently, securely, and reliably. System
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administrators are responsible for the day-to-day operations of IT infrastructure.
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Roles and Responsibilities
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Key Responsibilities:
User Management: Creating, modifying, and deleting user accounts
Security Management: Implementing security policies and monitoring threats
System Monitoring: Tracking system performance and resource usage
Backup and Recovery: Ensuring data protection and disaster recovery
Software Installation: Managing applications and system updates
Network Administration: Configuring and maintaining network services
Documentation: Maintaining system documentation and procedures
Daily Tasks:
Monitor system performance and logs
Respond to user support requests
Apply security patches and updates
Manage user accounts and permissions
Perform system backups
Troubleshoot hardware and software issues
Types of Operating Systems
,1. Windows Server
Characteristics: GUI-based, Active Directory integration, proprietary
Use Cases: Enterprise environments, Microsoft-centric organizations
Versions: Windows Server 2019, 2022
2. Linux/Unix
Characteristics: Command-line focused, open-source, highly customizable
Popular Distributions: Ubuntu Server, CentOS, Red Hat Enterprise Linux
Use Cases: Web servers, databases, cloud infrastructure
3. macOS Server
Characteristics: Apple ecosystem integration, limited enterprise use
Use Cases: Creative industries, small Apple-focused environments
2. Linux Administration Basics
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Linux Directory Structure
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Root Directory Structure:
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/ (root)
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├── /bin # Essential user binaries
├── /boot # Boot loader files
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├── /dev # Device files
├── /etc # Configuration files
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├── /home # User home directories
├── /lib # Shared libraries
├── /media # Removable media mount points
├── /mnt # Temporary mount points
├── /opt # Optional software packages
├── /proc # Process information
├── /root # Root user home directory
├── /sbin # System binaries
├── /tmp # Temporary files
├── /usr # User programs and data
└── /var # Variable data (logs, mail, etc.)
Important Directories:
/etc: System configuration files
/var/log: System log files
/home: User home directories
, /usr/bin: User executable programs
/proc: Virtual filesystem with system information
File Permissions & Ownership
Permission Types:
r (read): Permission to read file contents (4)
w (write): Permission to modify file contents (2)
x (execute): Permission to execute file or access directory (1)
Permission Groups:
Owner: The user who owns the file
Group: Users in the file's group
Other: All other users
Reading Permissions:
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bash
ls -l filename
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-rwxr-xr-- 1 user group 1024 Jan 15 10:30 filename
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||| |||
||| ||└── Other permissions (r--)
||| |└─── Group permissions (r-x)
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||| └──── Owner permissions (rwx)
||└──────── Number of hard links
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|└───────── File type (- = regular file, d = directory)
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└────────── File permissions
chmod Command:
bash
# Numeric method (octal)
chmod 755 filename # rwxr-xr-x
chmod 644 filename # rw-r--r--
chmod 600 filename # rw-------
# Symbolic method
chmod u+x filename # Add execute for owner
chmod g-w filename # Remove write for group
chmod o=r filename # Set other to read only
chmod a+r filename # Add read for all (a=all)
chown Command: