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SELinux (Security-Enhanced Linux) is a mandatory access control (MAC) security mechanism that provides an additional layer of security to the Linux kernel. By default, SELinux is enabled in CentOS/RHEL 7, but it runs in permissive mode, which means it logs security violations without blocking them. What is SELinux? SELinux is a security module developed by the NSA in partnership with Red Hat that enforces policies governing what actions processes and users can perform on the system. It uses predefined labels assigned to resources such as files, directories, sockets, and devices to define security contexts and control access. ... Read More
A Distributed Operating System is a type of system where applications run across multiple interconnected computers, functioning as a single unified platform. It extends network operating system capabilities by supporting higher levels of communication and integration between machines. For end-users, it appears as an ordinary centralized operating system while leveraging multiple CPUs and distributed resources. The system can share all resources including CPU, memory, disk storage, network interfaces, and computational nodes across different sites, effectively increasing the data and processing power available to the entire network. All processors connect through high-speed communication media like buses and network lines, with ... Read More
Windows Operating System is a type of operating system based on Graphical User Interface (GUI). It creates an interface between user and machine using graphical elements like icons, pictures, colors, and windows to make computing more intuitive and accessible. The Windows operating system was developed by Microsoft Corporation, an American multinational technology company founded by Bill Gates and Paul Allen. Windows is one of the most popular computer operating systems globally, with over 70% market share on desktop computers. The primary reason behind its popularity is its user-friendly interface, multitasking capabilities, and extensive hardware compatibility. ... Read More
SSH (Secure Shell) is a network protocol that enables secure communication between two systems. It establishes an encrypted connection to a remote server over unsecured networks like the internet, making it ideal for remote administration and file transfers. Unlike protocols such as Telnet or FTP, SSH encrypts all data transmission, preventing third-party interception. Importance of Enabling SSH on Debian 9 or 10 Enabling SSH on your Debian system provides crucial remote administration capabilities. System administrators can manage multiple servers from different locations without physical presence at each machine. This remote access minimizes infrastructure-related downtime by allowing quick issue ... Read More
Operating systems play a vital role in managing computer resources and providing a platform for executing programs. Two fundamental types are Time Sharing Operating Systems and Multiprogramming Operating Systems. While both aim to improve resource utilization and user experience, they differ significantly in their approach to achieving these goals. Time Sharing Operating Systems Time Sharing Operating Systems (TSOS) focus on providing an interactive computing environment where multiple users can simultaneously access the system and share its resources. TSOS achieves this by rapidly switching between different user programs using small time intervals called time slices or quantum, giving each ... Read More
Application Programming Interfaces (APIs) and system calls are both mechanisms that enable communication and service requests, but they operate at different levels of the computing stack. Understanding their differences is crucial for grasping how software components interact with each other and the operating system. Application Programming Interface (API) An API is a set of protocols, routines, and functions that allows different applications and devices to communicate and exchange data. It acts as an intermediary that takes requests from users or applications, informs the system about what needs to be done, and returns the appropriate response. APIs enable ... Read More
If you are familiar with command line interface, you have probably encountered a double-dash (--) in some of the commands you use. This article explains what the double-dash means and how it affects the behavior of shell commands. What is a Double-Dash in Shell Commands? A double-dash (--) is a syntax used in shell commands to signify the end of command options and the beginning of positional arguments. In other words, it separates command options from arguments that the command operates on. Many shell commands allow you to specify options or flags that modify the behavior of ... Read More
The Raspberry Pi is a popular, credit-card sized computer that can be used for various purposes such as media center, gaming console, and even as a web server. These devices run on different operating systems such as Raspbian (a version of Debian Linux), Windows 10 IoT Core, and Ubuntu among others. One of the key functionalities provided by these devices is the ability to connect remotely via Secure Shell (SSH). What is SSH? SSH (Secure Shell) is a network protocol that allows users to securely access remote computers over an unsecured network. It uses encryption to protect all ... Read More
A process and a program are fundamental concepts in operating systems, yet they are often confused. Understanding their differences is crucial for grasping how operating systems manage tasks and resources. What is a Program? A program is a passive entity that consists of a set of instructions written in a programming language. It is stored as an executable file on secondary storage (like a hard disk). A program by itself does not consume system resources like CPU time or memory until it is executed. Key characteristics of a program: It is a static entity stored on ... Read More
Linux is a popular operating system widely used for its open-source nature and flexibility. The Linux command line interface (CLI) provides powerful tools for system control and manipulation. However, there appears to be some confusion about "opt" as a command in Linux. Let's clarify what this actually refers to and explore the correct concepts. What Does "opt" Actually Mean in Linux? There is no standalone "opt" command in Linux. The term "opt" typically refers to command-line options (also called flags or switches) that modify how commands behave. These options are prefixed with hyphens and provide additional functionality to ... Read More