Here you can find how to’s related to Centos Operating System Administration.
Installation and Recovery¶
Installation (or setup) of a computer program (including device drivers and plugins), is the act of making the program ready for execution. Because the process varies for each program and each computer, programs (including operating systems) often come with an installer, a specialized program responsible for doing whatever is needed for their installation. Installation may be part of a larger software deployment process.
Installation typically involves code being copied/generated from the installation files to new files on the local computer for easier access by the operating system. Because code is generally copied/generated in multiple locations, uninstallation usually involves more than just erasing the program folder. For example, registry files and other system code may need to be modified or deleted for a complete uninstallation.
File System Management¶
A filesystem is the street grid of your hard drive. It’s a map of addresses to where data is located on your drive. Your operating system uses the filesystem to store data on the drive. There are a number of different types of filesystems. Some are better at handling many small files (ReiserFS), some are much better at large files and deleting files quickly (XFS, EXT4). The version of Unix you use will have picked a filesystem which is used by default, on Linux this is often EXT3. Understanding the way filesystems work is important when you have to fix issues related to disk space, performance issues with reading and writing to disk, and a host of other issues. In this section we will discuss creating partitions, file systems on those partitions, and then mounting those file systems so your operating system can use them.
A package manager is a collection of software tools that automates the process of installing, upgrading, configuring, and removing software packages for a computer’s operating system in a consistent manner. It typically maintains a database of software dependencies and version information to prevent software mismatches and missing prerequisites.
Packages are distributions of software, applications and data. Packages also contain metadata, such as the software’s name, description of its purpose, version number, vendor, checksum, and a list of dependencies necessary for the software to run properly. Upon installation, metadata is stored in a local package database.
Package managers are designed to save organizations time and money through remote administration and software distribution technology that eliminate the need for manual installs and updates. This can be particularly useful for large enterprises whose operating systems are based on Linux and other Unix-like systems, typically consisting of hundreds or even thousands of distinct software packages; in the former case, a package manager is a convenience, in the latter case it becomes essential.
A system configuration (SC) in systems engineering defines the computers, processes, and devices that compose the system and its boundary. More general the system configuration is the specific definition of the elements that define and/or prescribe what a system is composed of.
Alternatively the term system configuration can be used to relate to a model (declarative) for abstract generalized systems. In this sense the usage of the configuration information is not tailored to any specific usage, but stands alone as a data set. A properly-configured system avoids resource-conflict problems, and makes it easier to upgrade a system with new equipment.
Software monitors occur more commonly, sometimes as a part of a widget engine. These monitoring systems are often used to keep track of system resources, such as CPU usage and frequency, or the amount of free RAM. They are also used to display items such as free space on one or more hard drives, the temperature of the CPU and other important components, and networking information including the system IP address and current rates of upload and download. Other possible displays may include the date and time, system uptime, computer name, username, hard drive S.M.A.R.T data, fan speeds, and the voltages being provided by the power supply.
Less common are hardware-based systems monitoring similar information. Customarily these occupy one or more drive bays on the front of the computer case, and either interface directly with the system hardware or connect to a software data-collection system via USB. With either approach to gathering data, the monitoring system displays information on a small LCD panel or on series of small analog or LED numeric displays. Some hardware-based system monitors also allow direct control of fan speeds, allowing the user to quickly customize the cooling in the system.
A few very high-end models of hardware system monitor are designed[by whom?] to interface with only a specific model of motherboard. These systems directly utilize the sensors built into the system, providing more detailed and accurate information than less-expensive monitoring systems customarily provide.
kernel and Driver Configuration¶
The Linux kernel is a Unix-like computer operating system kernel. The Linux kernel is the most widely used operating system kernel in the world; the Linux operating system is based on it and deployed on both traditional computer systems, usually in the form of Linux distributions, and on embedded devices such as routers. The Android operating system for tablet computers and smartphones is also based atop the Linux kernel.
Kernel modules are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system.
Security and Authentication¶
Linux Security Modules (LSM) is a framework that allows the Linux kernel to support a variety of computer security models while avoiding favoritism toward any single security implementation. The framework is licensed under the terms of the GNU General Public License and is standard part of the Linux kernel since Linux 2.6. AppArmor, SELinux, Smack and TOMOYO Linux are the currently accepted modules in the official kernel.