Fedora™ Unleashed, 2008 edition

[email protected] ftp 0 * c

Related Fedora and Linux Commands

You use these commands to install, configure, and manage FTP services in Fedora:

> epiphany — A graphical GNOME browser supporting FTP

> ftp — A text-based interactive FTP command

> ftpcopy — Copy directories and files from an FTP server

> ftpcp — Retrieve data from a remote FTP server, but do not overwrite existing local files

> gftp — A graphical FTP client for GNOME

> konqueror — KDE's graphical web browser

> lftp — An advanced text-based FTP program

> nautilus — Red Hat's graphical file explorer and browser

> ncftp — A sophisticated, text-based FTP program

> sftp — Secure file transfer program

> smbclient — Samba FTP client to access SMB/CIFS resources on servers

> system-config-services — Red Hat's system service GUI admin utility

> vsftpd — The Very Secure FTP daemon

> webcam — A webcam-oriented FTP client included with xawtv

Reference

> http://www.wu-ftpd.org/ — wu-ftp official website.

> http://www.cert.org/ — Computer emergency response team.

> http://www.openssh.com/ — OpenSSH home page and source for the latest version of OpenSSH and its component clients, such as sftp.

> http://www.cert.org/tech_tips/anonymous_ftp_config.html — CERT anonymous FTP configuration guidelines.

> http://vsftpd.beasts.org/ — Home page for the vsftd FTP server.

> ftp://vsftpd.beasts.org/users/cevans/ — Download site for the latest releases of the vsftpd server.

CHAPTER 21 Handling Electronic Mail

Email is still the dominant form of communication over the Internet. It is fast, free, and very easy to use. However, much of what goes on behind the scenes is extremely complicated and would appear scary to anyone who does not know much about how email is handled. Fedora comes equipped with a number of powerful applications to help you build anything from a small email server right through to large servers handling thousands of messages.

This chapter shows you how to configure Fedora to act as an email server. We look at the options available in Fedora, as well as the pros and cons of each one. You will also learn how mail is handled in Linux, and to a lesser extent, UNIX.

How Email Is Sent and Received

Email is transmitted as plain text across networks around the world using SMTP (Simple Mail Transfer Protocol). As the name implies, the protocol itself is fairly basic, and it has been extended to add further authentication and error reporting/messaging to satisfy the growing demands of modern email. Mail transfer agents, or MTAs, work in the background, transferring email from server to server, allowing emails to be sent all over the world. You might have come across such MTA software such as Sendmail, Postfix, Fetchmail, Exim, or Qmail.

SMTP enables each computer through which the email passes to forward it in the right direction to the final destination. When you consider that there are millions of email servers across the world, you have to marvel at how simple it all seems.

Here is a simplified example of how email is successfully processed and sent to its destination:

1. [email protected] composes and sends an email message to [email protected].

2. The MTA at hudson.org receives andrew's email message and queues it for delivery behind any other messages that are also waiting to go out.

3. The MTA at hudson.org contacts the MTA at hudzilla.org on port 25. After hudzilla.org acknowledges the connection, the MTA at hudson.org sends the mail message. After hudzilla.org accepts and acknowledges receipt of the message, the connection is closed.

4. The MTA at hudzilla.org places the mail message into paul's incoming mailbox; paul is notified that he has new mail the next time he logs on.

Of course, several things can go wrong during this process. Consider these examples:

> What if paul does not exist at hudzilla.org? In this case, the MTA at hudzilla.org rejects the email and notifies the MTA at hudson.org of what the problem is. The MTA at hudson.org then generates an email message and sends it to [email protected], informing him that no paul exists at hudzilla.org (or perhaps just silently discards the message and gives the sender no indication of the problem, depending on how the email server is configured).

> What happens if hudzilla.org doesn't respond to hudson.org's connection attempts? (Perhaps the server is down for maintenance.) The MTA at hudson.org notifies the sender that the initial delivery attempt has failed. Further attempts will be made at intervals decided by the server administrator until the deadline is reached, and the sender then is notified that the mail is undeliverable.

The Mail Transport Agent