Chapter 8: Linux Servers on the LAN

8/14/2019 Chapter 8: Linux Servers on the LAN

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Chapter 8: Linux Servers on the LAN


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What Is Linux

Linux is a UNIX-like open source operating system.

Open source software is software in which the source code isavailable.

Linux actually refers to the kernel of the operating system. Thekernel is the operating systems centerpiece.

Other components of the operating system have their own namessuch as X-Windows , Apache and Sendmail . A collection of

components bundled with Linux is known as a distribution .


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What Is Linux Some versions of Linux are freely available for download off the

Internet.

Linux use on the LAN is growing as it can perform many of thefunctions that a Windows server can, without the associated

licensing costs.

A drawback of Linux is that often more complicated to configurethan Windows is. What an organization saves in licensing costs,it might spend on personnel to manage the Linux systems.

Linux computers generally co-exist on the LAN with Windowsand Novell servers and replace older UNIX servers.


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DistributionA specific collection of Linux and programs that run on Linux isknown as a distribution. Anyone can create their own Linuxdistribution with enough time and effort.

Several popular distributions are:RedHat Enterprise Linux . Subscription-based, includes support. Targetedat large corporate LANs. Aims to replace traditional UNIX vendors.

RedHat Fedora . Development branch of Redhat Enterprise Linux used totest new software. Freely available, but less stable than the Enterpriseversion.

Debian. Freely available and highly stable Linux distribution. Does notinclude the very newest versions of software, only those versions that have

proven stable.

Novell SUSE. Novells Linux distribution. Integrated closely with the Novell network operating system. Subscription based.

Mandrake. Popular beginner distribution of Linux. Freely available.


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Source and Packages Source code is the program language text, usually written in the

language C, in text file format.

A binary file is the result of compiled source code.

A dependency is another component of the operating system thatmust already be installed before the new program will function.Some, but not all, software source code will attempt a

dependency check prior to installation.

It can be difficult to uninstall software that you have installed fromthe source code.


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Source and Packages

Packages are pre-configured binary files for specific distributions.Package managers keep track of which packages have been

installed.

When you install software using a package manager , adependency check will occur. If the required packages are not present on the computer, the installation will abort.

Some distributions offer a tracking service that will notify you

when new versions of installed packages are available.


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Command Line Administration

Because of Linuxs UNIX roots, the primary method by which itis administered is the command line .

Commands are often followed by switches , which allowdifferent options to be used.

All administrative tasks can be performed from the commandline, either by issuing specific commands or editing text-basedconfiguration files .


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Command Line Administration Can be accessed without the need to run the X-Windows graphical

environment, which reduces CPU overhead. Can be accessed fromGUI as well.

Can be accessed remotely via encrypted SSH session. Extremely

low bandwidth means that servers can be administered over theslowest modem connections.

Command line administration can offer a more precise control of the operating system than GUI-based administration. The down

side is that it requires precise syntax. Use an incorrect commandswitch and you may get a very unintended result.

Scripts are written in languages like Perl to automateadministration tasks.


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X-Windows Most Linux services and applications do have GUI -based

configuration utilities as well.

Generally though, the GUI-based configuration utilities lack allof the options of command line utilities.

X-Windows can be run remotely, so that you can view graphicutilities running on remote computers.

There are some security issues withrunning X-Windows remotely, so it

is often better to use a remote desktop product such as VNC to remotelyconnect to a Linux GUI.


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Webmin Webmin is a Web-based remote administration tool that can be

run via Web browser.

Offers the ability to configure most Linux services.

Some tools are better than the Linux GUI versions. Command line

still offers the best functionality.


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Single Sign On

In Windows, you log on and authenticate against a domaincontroller. This means that you can use the same logonaccount on any computer for the domain.

Unlike Windows, Linux computers are designed primarily to be stand alone. To have a single sign on solution means thatyou must configure a NIS/NIS+ server.

A NIS+ (Network Information Service plus) server keeps a

copy of the account database each NIS+ client computer.

NIS+ is highly complicated to configure compared to ActiveDirectory .


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File and Print Sharing Linux files can be shared in several ways. The first is via NFS

and the second is via SAMBA . NFS is primarily used to share files with other Linux clients.Linux clients can mount an NFS share as a directory within their local file system.

SAMBA is primarily used to share filesand printers with Windows clients.

Windows Servers can be configured to

print directly to Linux printers. You createa shared printer on Windows Server 2003 which points to the Linux printer.

Windows clients then direct print jobsthrough the Windows Server 2003computer.


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SAMBA Samba allows Windows clients to access resources on Linuxcomputers.

When a request is made for a resource, the Linux computer uses aWindows server to authenticate the user.

Shared files appear to clients the same

as they would if hosted on a WindowsServer.


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Apache Web Server The most popular Web server in the world.

Has been in use since 1995.

Configuration is performed by editing httpd.conf file.

Supports multiple Web sites, differentiated by FQDN, IP and TCP

port. Can restrict access on basis of IP address, domain name, username,

and password.

Apache modules can be added to support different features, such

as scripting languages and encryption. Modules are add-on components that enhance Apachesfunctionality.

Apache modules can be added to support restrictions via digital

certificate.


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E-Mail Servers

Almost all Linux distributions come with a built in e-mailserver.

The most popular is Sendmail . Sendmail supports POP3 ,IMAP4 , and SMTP .

Sendmail is configured by editing sendmail.cf . It has areputation as being very difficult to fine tune.

Another popular mail server is Postfix . Postfix was designedto be a simpler to administer alternative to Sendmail.


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Summary A Linux distribution is a collection of utilities bundled around the

Linux kernel. The most complete administrative interface for Linux is thecommand line. GUI and Web based administration are possible, butdont always offer the same number of configuration options.

When sharing files to UNIX or Linux clients, use NFS. Whensharing files to Windows clients, use SAMBA.

SAMBA allows a Linux computer to use a Windows Server toauthenticate Windows clients.

Apache Web server is the most deployed Web server in the world.Add-in modules extend Apaches functionality.

Sendmail and Postfix are popular Linux mail servers. Sendmail is

more fully featured, but more complex to configure.


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Discussion Questions

Which mail server was designed as a simpler to administer alternative to sendmail?

Describe the difference between source and packages?

What service should you install to provide single sign oncapabilities to Linux?

What do Apache modules do?

What are the disadvantages to command-lineadministration?

Chapter 8: Linux Servers on the LAN

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