One Pager Cheat Sheet

• Linux is an open-source, Unix-like, freely-distributable computer operating system (OS) built around the Linux Kernel, responsible for managing system hardware and resources, and considered quicker and more secure than Windows, as demonstrated by the comprehensive list of Linux interview questions in this article.
• Linux is composed of five distinct elements, such as the Kernel, System Libraries, System Utility, Hardware and Shell, which together form its System Architecture.
• Popular Linux distributions include Ubuntu, Debian, SUSE Linux, Gentoo, and Fedora.
• The Linux OS's kernel is a primary component, connecting the hardware and software of the system and serving as a low-level system software that loads on startup, performing functions such as managing RAM, controlling processor time, and managing peripherals.
• BASH (Bourne Again Shell) is a command language interpreter that has additional capabilities such as command-line editing, making it the default user shell on most Linux installations and a non-compiled, interpreted process that can be executed in the terminal window.
• Linux users have access to three types of permissions (read, write, and execute) that can be set using the chmod command.
• The permission readout for a file with reading permissions granted to the user and writing and executing permissions granted to the group and other is r---wx-wx, indicating that the user can Read the file but not Write or Execute it, while the group and other have Write and Execute permissions.
• The most popular Linux bootloader, LILO, is used to load Linux into memory and launch the OS, as well as finding, identifying, loading, and running the kernel.
• A daemon is software that runs in the background on Linux and Unix systems without requiring any user input.
• Cron and anacron are Linux programs used for scheduling automatic recurring tasks at specific times, though they function slightly differently.
• A process in Linux is in one of five states—Created/Ready, Running, Waiting, Terminated, and Zombie—which determine its current activity and whether it has ended or needs resources.
• Anacron is a scheduling program that runs commands at certain times, but not every hour; it is useful for non-time dependent tasks, but not designed to be a real-time scheduler.
• Anacron automatically schedules jobs for execution and tracks times when the system was not running, typically run once a day by the cron daemon.
• To terminate a running Linux process, use the ps command to find its process id, and then run the kill command with that Id as an argument.
• The main advantage of pkill over kill is that it allows you to terminate a process without needing to know its exact process id, but instead by specifying its name or other attributes.
• Boldly run the locate command to find a file location in Linux.