Running Linux, 5th Edition - Matthias Kalle Dalheimer [432]
Apache also provides a utility called apachectl that is more convienent for starting, stopping, and reloading the httpd process. In particular, calling:
apachectl configtest
is a good way of checking whether the configuration file is actually correct before starting the server. Finally, we should mention that you can also start, restart, and stop Apache by using /etc/init.d/apache plus one of the parameters start, restart, or stop.
Of course, in order to request documents via HTTP from your browser, you'll need to write them, something that we cannot cover in this book. Two good sources for HTML information are the O'Reilly books HTML & XML: The Definitive Guide and HTML Pocket Reference by Jennifer Niederst. To set up a back-end database to your web server, start with Chapter 25.
Chapter 23. Transporting and Handling Email Messages
Electronic mail (email ) is one of the most desirable features of a computer system. You can send and receive email on your Linux system locally between users on the host and between hosts on a network. You have to set up three classes of software to provide email service. These are the mail user agent or mailer, the mail transport agent (MTA), and the transport protocol.
The mailer provides the user interface for displaying mail, writing new messages, and filing messages. Linux offers you many choices for mailers. They are always being improved, and a particular mailer may provide certain features, such as the ability to serve as a newsreader or as a web browser.
Mailers tend to differ in terms of their MIME support. (MIME stands for Multipurpose Internet Mail Extensions. It is really not multimedia-specific, but more a general standard for describing the contents of email messages.) Some do it better than others. It's difficult to give a recommendation here, though, since all mailers are continually moving toward better MIME support. Also, the problem is often not with the mail software, but rather with the need to register MIME types with the right viewer/handler applications in your environment.
The mailer relies on the MTA to route mail from one user to another, whether locally or across systems. The MTA in turn uses a transport protocol, usually either Unix-to-Unix Copy (UUCP, a very old protocol that was once common and has almost died out in the Western world, but is still common in regions with slow and unreliable dial-up lines) or Simple Mail Transport Protocol (SMTP), to provide the medium for mail transfer.
There are a number of possible scenarios for using email on a Linux system, and depending on those scenarios, you will have to install a different set of software packages. However, no matter which option you choose, you will always need a mailer.
The first scenario applies to dial-up access to the Internet via an Internet service provider (ISP). In this scenario, there is often only one user on the Linux machine, although this is not a requirement. The ISP accepts your mail from the Internet and stores it for you on its hard disks. You can then retrieve the mail whenever you want by using the common Post Office Protocol (POP3) or the newer Internet Message Access Protocol (IMAP). Outgoing mail in this scenario is almost exclusively sent via the SMTP protocol, which is universally used to transport mail over the Internet.
In the easiest case, you use your mailer both to retrieve the mail via POP3 or IMAP and to send it back via SMTP. When you do this, you do not even need to set up an MTA because the mailer handles everything. This is not terribly flexible, but if all you want is to access your mail easily, this might be an option for you. Mailers that support this include KMail from KDE and Mozilla's built-in