Chapter Summary

   

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Network services are used as client/server applications on UNIX. Server applications are started as daemons or are invoked using inetd . Common server applications use well-defined ports for communication. System-wide security of commands starting with the letter r is controlled using the /etc/ hosts .equiv file. Any user can also create a $HOME/.rhosts file in the home directory to allow or deny access to his or her account by other users over the network. Security of inetd is controlled using the /var/adm/inetd.sec file. By using this file, selective hosts can be allowed or denied access to services.

If a service is started as a daemon at system boot time, its control files are created in /sbin/rc n .d directories where n represents a system run level. If a service is started with the help of inetd , it is configured using the /etc/inetd.conf file, where a complete path to the server process is defined. The inetd daemon uses the /etc/services file to get service names and corresponding port numbers for defined services.

Ports opened by server processes and established connections can be listed at any time using the netstat -a command. SAM can be used to enable or disable selected services.

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