Red Hat Enterprise Linux 5 Administration Unleashed

398CHAPTER 19Explaining Other Common Network ServicesTo start the server, execute the service ntpd start command. To stop it, use the servicentpd stop command. To configure the system to start the NTP server at boot time, runthe chkconfig ntpd on command.TIPCheck /var/log/messages for messages from ntpd to verify its status or to readerror messages.Allowing NTP ConnectionsBoth the NTP server and clients connecting to an NTP server need to allow incoming andoutgoing UDP connections on port 123.If custom IPTables rules are being used, refer to Chapter 24 for details on how to allowthese ports.If using the Security Level Configuration tool, start it by selecting Administration,Security Level and Firewall from the System menu on the top panel of the desktop orby executing the system-config-securitylevel command. Enter the root password whenprompted if running as a user. In the Other ports area, click Add to specify the NTP port.Creating a Network Printer with CUPSIn Chapter 2, “Post-Installation Configuration,” you learned how to configure a localprinter or connect to a shared printer. The same graphical interface can also be used toshare a printer with other systems on the network using the Common UNIX PrintingSystem, also known as CUPS. The cups RPM package must be installed.From the System menu on the top panel of the desktop, select Administration, Printingto start the tool, or execute the command system-config-printer. The root password isrequired to continue. The interface shows all configured printers, both locally attachedand shared printers accessible by the system.To share a printer over the network, first configure it as a local printer as described in the“Printer Configuration” section of Chapter 2. After the local printer is added, select theprinter and make sure the Shared state is checked at the bottom of the Settings tab.Then click on Server Settings in the left menu as shown in Figure 19.4 and select Sharepublished printers connected to this system. Click Apply to enable the changes. Allprinters with shared state enabled are broadcast over the network for others to connect tofor printing.By default, if sharing is enabled, anyone can print to the shared printers on the server. Torestrict printer access based on the user sending the print request, select the printer fromthe list on the left, and go to the Access control tab. There are two options:. Allowing printing for everyone except these users. Deny printing for everyone except these users