Chapter 11.  System Administration: Core Concepts


11. System Administration: Core Concepts

IN THIS CHAPTER


The job of a system administrator is to keep one or more systems in a useful and convenient state for users. On a Linux system, the administrator and user may both be you, with you and the computer being separated by only a few feet. Or the system administrator may be halfway around the world, supporting a network of systems, with you being simply one of thousands of users. A system administrator can be one person who works part-time taking care of a system and perhaps is also a user of the system. Or the administrator can be several people, all working full-time to keep many systems running.

A well-maintained system

  • Runs quickly enough so users do not get too frustrated waiting for the system to respond or complete a task.

  • Has enough storage to accommodate users' reasonable needs.

  • Provides a working environment appropriate to each user's abilities and requirements.

  • Is secure from malicious and accidental acts altering its performance or compromising the security of the data it holds and exchanges with other systems.

  • Is backed up regularly, with recently backed-up files readily available to users.

  • Has recent copies of the software that users need to get their jobs done.

  • Is easier to administer than a poorly maintained system.

In addition, a system administrator should be available to help users with all types of system-related problemsfrom logging in to obtaining and installing software updates to tracking down and fixing obscure network issues.

of this book breaks system administration into seven chapters:

  • covers the core concepts of system administration, including Superuser, system operation, the Red Hat configuration tools and other useful utilities, general information about setting up and securing a server (including a section on DHCP), and PAM.

  • covers files, directories, and filesystems from an administrator's point of view.

  • covers installing software on the system, including how to use yum, pirut, Red Hat Network (RHN), up2date, BitTorrent, and wget.

  • discusses how to set up local and remote printers that use the CUPS printing system.

  • explains how to rebuild the Linux kernel.

  • covers additional system administrator tasks and tools, including setting up users and groups, backing up files, scheduling tasks, printing system reports, and general problem solving.

  • goes into detail about how to set up a LAN, including setting up and configuring the network hardware and configuring the software.

Because Linux is configurable and runs on a variety of platforms (Sun SPARC, DEC/Compaq Alpha, Intel x86, AMD, PowerPC, and more), this chapter cannot discuss every system configuration or every action you will have to take as a system administrator. Instead, this chapter seeks to familiarize you with the concepts you need to understand and the tools you need to use to maintain a CentOS Linux or Centos Linux system. Where it is not possible to go into depth about a subject, the chapter provides references to other sources.

This chapter assumes that you are familiar with the following terms:

block device (page )

filesystem (page )

root filesystem (page )

daemon (page )

fork (page )

runlevel (page )

device (page )

kernel (page )

signal (page )

device filename (page )

login shell (page )

spawn (page )

disk partition (page )

mount (page )

system console (page )

environment (page )

process (page )

X server (page )


Tip: If something does not work, see if the problem is caused by SELinux

If a server or other system software does not work properly, especially if it displays a permissions-related error message, the problem may lie with SELinux. To see if SELinux is the cause of the problem, put SELinux in permissive mode and run the software again. If the problem goes away, you need to modify the SELinux policy. Remember to turn SELinux back on. For more information refer to "" on page .