14.1. The File Transport Protocol ............................................................................. 21314.2. FTP Servers...................................................................................................... 21414.3. Files Installed with vsftpd............................................................................. 21414.4. Starting and Stopping vsftpd......................................................................... 21514.5. vsftpd Configuration Options........................................................................ 21614.6. Additional Resources ....................................................................................... 224III. Security Reference.................................................................................................................... 22715. Pluggable Authentication Modules (PAM)..................................................................... 22915.1. Advantages of PAM ......................................................................................... 22915.2. PAM Configuration Files ................................................................................. 22915.3. PAM Configuration File Format ...................................................................... 22915.4. Sample PAM Configuration Files .................................................................... 23215.5. Creating PAM Modules ................................................................................... 23415.6. PAM and Administrative Credential Caching.................................................. 23415.7. PAM and Device Ownership............................................................................ 23515.8. Additional Resources ....................................................................................... 23616. TCP Wrappers and xinetd............................................................................................ 23916.1. TCP Wrappers.................................................................................................. 23916.2. TCP Wrappers Configuration Files.................................................................. 24016.3. xinetd............................................................................................................. 24616.4. xinetd Configuration Files............................................................................. 24716.5. Additional Resources ....................................................................................... 25117. iptables ....................................................................................................................... 25317.1. Packet Filtering ................................................................................................ 25317.2. Differences between iptables and ipchains ............................................. 25417.3. Options Used within iptables Commands................................................... 25517.4. Saving iptables Rules .................................................................................. 26117.5. iptables Control Scripts............................................................................... 26117.6. ip6tables and IPv6....................................................................................... 26317.7. Additional Resources ....................................................................................... 26318. Kerberos .......................................................................................................................... 26518.1. What is Kerberos?............................................................................................ 26518.2. Kerberos Terminology ..................................................................................... 26618.3. How Kerberos Works ....................................................................................... 26818.4. Kerberos and PAM........................................................................................... 26918.5. Configuring a Kerberos 5 Server ..................................................................... 26918.6. Configuring a Kerberos 5 Client ...................................................................... 27118.7. Additional Resources ....................................................................................... 27219. SSH Protocol................................................................................................................... 27519.1. Features of SSH ............................................................................................... 27519.2. SSH Protocol Versions..................................................................................... 27619.3. Event Sequence of an SSH Connection ........................................................... 27619.4. OpenSSH Configuration Files ......................................................................... 27819.5. More Than a Secure Shell................................................................................ 27919.6. Requiring SSH for Remote Connections ......................................................... 28019.7. Additional Resources ....................................................................................... 281IV. Appendixes ................................................................................................................................ 283A. General Parameters and Modules .................................................................................... 285A.1. Specifying Module Parameters ......................................................................... 285A.2. SCSI parameters................................................................................................ 285A.3. Ethernet Parameters .......................................................................................... 286Index................................................................................................................................................. 291Colophon.......................................................................................................................................... 305