Red Hat Enterprise Linux 5 Administration Unleashed

xiiRed Hat Enterprise Linux 5 Administration Unleashed17 Securing Remote Logins with OpenSSH 355Allowing Connections...................................................................355Configuring the Server ..................................................................356Retaining Keys After Reinstalling .............................................356Connecting from the Client ...........................................................358Logging In to a Remote System ...............................................358Executing a Command Remotely ............................................359Transferring Files Securely ......................................................359Creating a Passphrase ............................................................361Remembering the Passphrase ..................................................363X11 Forwarding....................................................................364Port Forwarding ...................................................................365Logging Connections ....................................................................366Summary ....................................................................................36618 Setting Up an Email Server with Sendmail 367Understanding Email Concepts.......................................................367Configuring Sendmail ...................................................................370Using SSL Encryption ............................................................372Starting and Stopping the Server .............................................373Using POP and IMAP ....................................................................374Enabling POP and IMAP ........................................................374Enabling POP and IMAP with SSL............................................375Logging Sendmail Connections.......................................................376Allowing Email Connections ..........................................................377Summary ....................................................................................37819 Explaining Other Common Network Services 379The xinetd Super Server .................................................................379Configuring the xinetd Server.................................................379Allowing xinetd Connections .................................................384Transferring Files with FTP .............................................................387FTP and SELinux ..................................................................387Configuring the FTP Server.....................................................388Allowing Anonymous FTP ......................................................389Allowing FTP Connections .....................................................391Connecting from an FTP Client ..............................................392Logging FTP Connections ......................................................394Keeping Accurate Time with NTP ....................................................395Connecting to NTP from a Client ............................................395Configuring the NTP Server....................................................397Allowing NTP Connections ....................................................398Creating a Network Printer with CUPS .............................................398Summary ....................................................................................400