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.The virtual host example lines read as follows:# VirtualHost ip.address.of.host.some_domain.com# ServerAdmin webmaster@host.some_domain.com# DocumentRoot /www/docs/host.some_domain.com# ServerName host.some_domain.com# ErrorLog logs/host.some_domain.com-error_log# CustomLog logs/host.some_domain.com-access_log common# /VirtualHostUncomment all of the lines, and add the correct information for the virtual host.In the first line, change ip.address.of.host.some_domain.com to your server s IP ad-dress.Change theServerNameto a valid DNS name to use for the virtual host.You will also need to uncomment one of theNameVirtualHostlines below:#NameVirtualHost 12.34.56.78:80#NameVirtualHost 12.34.56.78Next change the IP address to the IP address and port, if necessary, for the virtual host.If you set up a virtual host and want it to listen on a non-default port, you will need to setup a virtual host for that port and add aListendirective for corresponding to that port.Then add the port number to the first line of the virtual host configuration as in the followingexample:VirtualHost ip_address_of_your_server:12331Chapter 15.Apache 205This line would create a virtual host that listens on port 12331.You must restart httpd to start a new virtual host.See Section 15.2 for instructions on howto start and stophttpd.Comprehensive information about creating and configuring bothname-based and IP address-based virtual hosts is provided on the Web athttp://httpd.apache.org/docs/vhosts/.Please check the Apache.org s virtual hostdocumentation for more details on using virtual hosts.15.6.Additional ResourcesTo learn more about Apache, refer to the following resources.15.6.1.Useful Websites" http://httpd.apache.org  The official website for the Apache Web server with documen-tation on all the directives and default modules." http://www.modssl.org  The official website for mod_ssl." http://www.apacheweek.com  A comprehensive online online weekly about all thingsApache.15.6.2.Related Books" Apache Desktop Reference by Ralf S.Engelschall; Addison WesleyWritten by ASF member and mod_ssl author Ralf Engelschall, the Apache Desktop Referenceprovides a concise but comprehensive reference guide to using Apache at compilation,configuration, and run time.This book is available online at http://www.apacheref.com/." Professional Apache by Peter Wainwright; Wrox Press LtdProfessional Apache is from Wrox Press Ltd s "Programmer to Programmer" series and isaimed at both experienced and novice Web server administrators." Administering Apache by Mark Allan Arnold; Osborne Media GroupThis book is targeted at Internet Service Providers who aim to provide more secure ser-vices." Apache Server Unleashed by Richard Bowen, et al; SAMS BOOKSAn encyclopedic source for Apache." Apache Pocket Reference by Andrew Ford, Gigi Estabrook; O ReillyThis is the latest addition to the O Reilly Pocket Reference series.206 Chapter 15.ApacheChapter 16.EmailEmail is one of the most widely used services on the Internet.Red Hat Linux offers manyways for you to utilize email, whether you are a desktop user or a system administrator.This chapter looks at popular email protocols that are in use today and various programsdesigned to accomplish different types of tasks when dealing with email.16.1.ProtocolsEmail, like other network services, uses a variety of protocols.These protocols allow differ-ent machines, often running different operating systems and utilizing different email pro-grams, to communicate with one another and transfer mail so it arrives in the proper place.The following protocols are those most commonly used to transfer email from system tosystem.16.1.1.IMAPThe Internet Message Access Protocol (IMAP) is a method used by email client applicationsto access remotely stored messages.When using IMAP, commonly called IMAP4 after theversion of the protocol used, the email messages remain on the remote mail server, wherethe user can read or delete them and create, rename, or delete mailboxes to store the email.In addition, IMAP is fully compatible with important Internet messaging standards, suchas the Multipurpose Internet Mail Extensions (MIME), to allow attachments to be received.Many email clients that use IMAP can also be configured to cache a copy of the messages lo-cally, so that you can browse previously read messages when you are not directly connectedto the IMAP server.IMAP is primarily utilized by users that may access their email using multiple machines,as messages are stored in a central location and can be accessed by any system with anIMAP mail client and a connection to the remote IMAP server.Also, users that connect to theInternet or a private network via a low-bandwidth connection often use IMAP because onlythe email header information is pulled off at first.This allows them to defer the downloadingof messages containing large attachments until a time when their limited bandwidth is notin use.In the same way, email that the user does not want can be deleted without viewingthe message body, saving the need to even download it through their network connection.The Request for Comment (RFC) documents that cover IMAP contain the assorted details andspecifics about how the protocol is designed to work.RFC-1730 first defined the way IMAPis used in version 4, but RFC-2060 discusses the current IMAP implementation used withmany IMAP servers, called version IMAP4rev1.The imap package in Red Hat Linux allows users to connect to your system and receivetheir email using IMAP.Secure IMAP connections are supported through SecureSocket Layer (SSL) technology built into the imapd daemon, allowing it to use the/usr/share/ssl/certs/imapd.pemcertificate file.Thestunnelprogram is not required toprovide SSL-encryption for IMAP connections, though it can be used.See Section 16.6.2 formore information concerning these two encryption options.Other free, as well as commercial, IMAP clients and servers are available, many of whichextend the IMAP protocol and provide additional functionality.A comprehensive list can befound at http://www.imap.org/products/longlist.htm.208 Chapter 16.Email16.1.2.POPThe Post Office Protocol (POP) allows email clients to pull off email from remote servers andsave those messages on their local machine.Most POP email clients are automatically con-figured to delete the message on the email server after it has been successfully transferred tothe client s system, though this can usually be changed.To connect to a POP server, the email client opens a TCP connection to port 110 on the server.At the time the connection is made, the POP server sends the POP client a greeting, afterwhich the two machines send each other commands and responses specified in the protocol.As part of this communication, the POP client is asked to authenticate itself in what is calledthe Authentication State, where the user s username and password are sent to the POP server.If authentication is successful, then the POP client moves on to the Transaction State, wherecommands likeLIST,RETR, andDELEcan be used to list, download, and delete the messagesfrom the server, respectively [ Pobierz całość w formacie PDF ]