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Mass Storage Management deals with the organization and optimization of secondary storage devices, primarily disks, in modern operating systems. Disks provide the bulk of secondary storage and require efficient management algorithms to handle data access requests. Disk Structure Modern disks contain concentric tracks divided into multiple sectors. The disk structure can be visualized as follows − Disk Structure Sector ... Read More
A bootstrap program is the first code that is executed when the computer system is started. The entire operating system depends on the bootstrap program to work correctly as it loads the operating system. Bootstrap Program Loading Process ROM (Non-volatile) Bootstrap Loads RAM (Volatile) Operating System ... Read More
The truncate command is used to shrink or extend the size of a file to a specified size in Linux. Unlike deletion commands, truncate cannot remove files but can modify their contents and size. When reducing file size, if the specified size is smaller than the actual size, the extra data will be permanently lost. Syntax The general syntax of the truncate command is as follows: truncate OPTION... FILE... Options Brief description of options available in the truncate command: Option Description -c, --no-create Do not ... Read More
Docker containers are built using Dockerfiles which contain step-by-step instructions to define the container environment. Among the various Dockerfile instructions, CMD and ENTRYPOINT are two critical commands that define what processes run inside containers. While they appear similar, they have distinct behaviors and use cases. Before exploring their differences, it's important to understand the two forms of writing instructions in Dockerfiles: Shell Form vs Executable Form Shell Form In shell form, the command is processed by a shell (/bin/sh -c). This allows shell features like variable expansion and command substitution. INSTRUCTION command param1 param2 ... Read More
The Linux kernel manages processes through five distinct states that define their current execution status and resource allocation. Understanding these states is crucial for system administrators and developers working with process management. The Five Process States Running (TASK_RUNNING) − The process is either currently executing on the CPU or is ready to run and waiting in the run queue. This is the most active state where the process can access system resources and CPU time. Interruptible Sleep (TASK_INTERRUPTIBLE) − The process is blocked and waiting for a specific event, signal, or resource to become available. It can ... Read More
Loadable Kernel Modules (LKMs) are object files containing code that can extend the running kernel, also known as the base kernel. These modules allow dynamic addition of functionality such as device drivers, file systems, and system calls without modifying the core kernel code. Loadable Kernel Modules Architecture Base Kernel Core OS Functionality Process Management, Memory Module Interface File ... Read More
The sort command in Linux is used to arrange lines of text files in a specified order. By default, it sorts lines alphabetically in ascending order, but it offers numerous options to customize the sorting behavior based on different criteria such as numeric values, months, or reverse order. Syntax The general syntax of the sort command is as follows: sort [OPTION]... [FILE]... sort [OPTION]... --files0-from=F Common Sort Options Option Description -b, --ignore-leading-blanks Ignore leading blanks when sorting -d, --dictionary-order Consider only blanks and alphanumeric ... Read More
In operating systems, instructions are classified into two main categories based on their access level and potential impact on system security and stability. Privileged instructions can only be executed in kernel mode, while non-privileged instructions can be executed in user mode. This classification ensures system protection and controlled access to critical resources. Privileged Instructions Privileged instructions are machine-level instructions that can only be executed when the processor is operating in kernel mode (also called privileged mode). These instructions have direct access to system resources and can potentially compromise system security if misused. Examples of Privileged Instructions ... Read More
The system boot process is the sequence of steps that occurs when a computer starts up, transforming it from a powered-off state to a fully operational system. The BIOS, operating system, and hardware components must all work correctly for successful booting. System Boot Process The boot process involves several distinct phases, each with specific responsibilities for system initialization. System Boot Process Flow Power On CPU Initialization ... Read More
The split command is used to divide large files into smaller, more manageable pieces in Linux systems. By default, it creates output files with 1000 lines each and uses 'x' as the filename prefix. For example, if no output filename is specified, the split files will be named xaa, xab, etc. When a hyphen (-) is used instead of an input file, the command reads data from standard input. Syntax The general syntax of the split command is as follows: split [OPTION]... [FILE [PREFIX]] Command Options Option Description ... Read More