Linux Servers

GNU/Linux Servers

NFM 2008

Majour Servers
● Apache HTTP Server
● Squid Proxy and Cache
● Samba Server
● FTP Server [vsftpd]
● Database Server [Postgresql,Mysql,Sqllite]
● Email Server [sendmail,postfix]
● Firewall

Introduction to Apache
● The Apache group was formed in 1995
● Apache => A Patchy Server
● Largely because the patches to NCSA server that
resulted in this new webserver. It actually got its
name from the native American Tribe
● Apache Version 1.0 was released in December, 1995
● World's most used webserver since April, 1996
● http://news.netcraft.com/archives/web_server_survey.ht
● 50.43% october 2008

Facts
● Easy administration using web based
interface [webmin]
● No cost to setup a server.
● As easy as download a CD and install.
● Lower maintenance.
● Keeps running for years.
● Better Security than IIS

Features
● Virtual Hosting
● Acess Configuration
● Security
● mod_rewrite

Single website/Virtual Hosting
● Single Website
● The host definitions go into the main configuration
● Any connection to the server returns the same set of page
● Virtual Hosting
● Ip based virtual hosting
– Multiple IP addresses to the same machine
● Name based virtual hosting
– Multiple domain names to the same IP address
● Port based virtual hosting
– Hanlding the request in a particular port

Access Configuration
● Allow from
● Allow access from the given networks and addresses or
when the environment satisfies a condition
● Deny from
● Deny access from the given networks and addresses or
when the environment satisfies a condition

Security
● mod_ssl
● Set SSLCertificateFile and SSLCertificateKeyFile
● Digital certificates from OpenSSL
● mod_security
● can the incoming requests for attacks and can
proactively prevent attacks on the server
● mod_userdir
● nables “~username” urls for user

mod_rewrite
● Rewrite Incoming Url based on regular
expressions
● Help Making Clean Urls in dynamic content
generation like php
● Can Use Regular Expressions for rewrite
● Using .htaccess in each directory

More ...
● mod_proxy can take care of proxy, both
reverse and forward
● Perl, Python and Ruby have script engines
that come as modules to Apache
● Apache is the most used webserver, since
1996 :)
● 59% of world wide web servers are apache

Introduction to Proxy
● In a typical setup a WebProxy requests
pages from the Internet on behalf of the clients
on the local network and serves them to the
local clients.
– Enhances security on LAN
– When caching is enabled, gives a better browsing
experience
● Proxy servers also cache data and avoid
redundant and repeated requests to servers for
the same data.
●

Features of Squid
● Web Proxy and Cache for HTTP, FTP
● DNS Lookup Cache
● Reverse Proxy to accelerate speed of web
servers
● Access Control Lists
● Bandwidth management

Network File Sharing Server

Samba

Introduction to SMB
● NetBIOS by IBM and Sytec
● NetBIOS + Disk I/O redirection => SMB
– Server Message Block Protocol by Microsoft
– Now called the CIFS [Common Internet File System]
● Windows machines advertise their services
and presence on the network using this
protocol
● The “Network Neighbourhood”

Introduction to Samba
● Andrew Tridgell published his code in early
1992
● Actual development started two years later
● Opening windows to the wider world
● Samba runs on unix platforms, but speaks to
Windows clients like a native windows machine
● Lets you share files and printers over the
network
● Works with SMB as well as its latest form
CIFS

Features Samba
● File and Printer sharing
● Access controls
● Remote Logons
● Work As a part of windows Network
● Can Act as the Primary Domain Controller
● SWAT (Samba Web Administration Tool)

Introduction to FTP
● File Transfer Protocol
● Criticisms
– Passwords are sent in cleartext
– Multiple TCP/IP connections needed
– No integrity check in case of connection failures
● Alternatives
– SFTP and FTPS for secure copying
– Secure Copy or SCP is nowadays largely used

Features of vsftpd
● A simple FTP server
● Anonymous access
● Security considerations
● Easy Configuration

Active Directory

Open LDAP

Features
● Active Directory is essentially LDAP and
Kerberos tied together (although slightly
Modified)
● OpenLDAP is the usual LDAP implementation
● If you decide to keep Active Directory, Samba
version 3.0 or higher is needed to integrate well
with it

Domain Name System (DNS) server

BIND
[Berkeley Internet Name Domain]

Features of BIND
● Berkeley Internet Name Domain (BIND) is one
of the many industry standard Open Source
packages that make up much of the Internet
infrastructure.
● Domain name serving is one of the easiest (and
most transparent to the end user) conversions
you' face.
● BIND works from plain text configuration files,
not a GUI.

Dynamic Host Configuration
Protocol
(DHCP) server

ISC’s DHCP

Features
● ISC’s DHCP is industry standard Open Source
Package
● it works better with Windows clients than a
Windows DHCP server
● DHCP server keeps its configuration data in
a .mdb file

Web Application Server (Java)
● Lots of products in this area. Probably the
same ones that you run on Windows are
available for Linux
– WebSphere
– BEA WebLogic
– Iplanet
– Jboss
● Installation, configuration and management
should be the same or very similar across
platforms

Remote Access Server
● Use the pppd package that comes with your
distribution
● pppd supports a variety of authentication
protocols, such as PAP, CHAP, and RADIUS
● IP forwarding must be turned on in the Linux
kernel
● Kpp GUI is available

Email Server
● lots of choices on Linux
● Sendmail,
● Exim,
● Postfix,
● The email delivery piece is the easy part

Groupware Server
● Bynari’s Insight server is one, but only scales
up to about 50,000 email boxes.
● Ximian Insight Connector (now owned by
Novell) is another
●

Database Server
● The two most popular Open Source ones are
● MySQL and PostgreSQL
● MySQL easy flexible
● PostgreSQL is strong and enterprise class.

Firewall
● Linux comes with a native firewall capability
● Linux also has native support for Network
Address Translation (NAT), also known as IP
masquerading
● The iptables command is what is used to create
firewall and NAT rules. There are GUI front
ends available to make that easier.
● • Commercial firewalls are also available for
Linux, such as Check Point’s Firewall1,
Phoenix, StoneGate, etc.

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