![]() Some of the more common and useful Telnet server options include: In the case of inetd, you place these options at the end of the Telnet server's configuration line for xinetd, you place them on the server_args line, which you may need to add to the configuration file. Whether you launch the server via inetd or xinetd, you can add a few options that modify the server's behavior. In xinetd, the disable = yes option disables the server this line must be changed to read disable = no to activate the server. To use Telnet, you must remove that character. In the case of inetd, the line defining the Telnet server is commented out by placing a hash mark ( #) at the start of the line. Many systems disable Telnet by default in the super server configuration files. Linux distributions that use xinetd typically place configurations for individual servers in files located in /etc/xinetd.d the Telnet server's file (typically called telnet or telnetd) looks like this: service telnet An equivalent configuration for a system that uses xinetd doesn't use TCP Wrappers because xinetd incorporates features similar to those provided by TCP Wrappers. This example calls the server via the TCP Wrappers ( tcpd) program, which provides added security options. A typical Telnet server configuration looks something like this: telnet stream tcp nowait root /usr/sbin/tcpd in.telnetd The inetd super server is controlled through the /etc/nf file, which devotes one line to each server it manages. If neither is present, you may need to install, or at least launch, your distribution's super server package. If you're not sure which super server your system runs, type ps ax | grep inetd and examine the output for a process called inetd or xinetd. Typically, Telnet servers are launched from super serversusually inetd or xinetd. Although Telnet servers come from several different sources, basic configuration and use is fairly consistent. (Kerberized or other encrypting variants are also available.) The server program itself is usually called telnetd or in.telnetd, and is usually stored in /sbin or /usr/sbin. Likely package names include telnetd, telnet-server, netkit-telnetd, telnet-bsd, and utelnetd, among others. Launching a Telnet ServerĪll major Linux distributions ship with a Telnet server, although many don't install it by default. Although Telnet's security features are severely lacking, you may be able to improve matters using a Kerberized Telnet or by implementing limited access controls in your super server. Telnet servers are simple and easy to configure in Linux the worst complication is knowing whether you're using the inetd or xinetd super server. Thus, you should use Telnet only when you have no other choice (say, because of limited client OS software options) or on highly protected local networks. Telnet's unencrypted nature, though, is a major drawback. ![]() As one of the oldest and most popular remote text-mode login tools available, Telnet is an excellent choice for compatibilityjust about every OS with a TCP/IP stack comes with a Telnet client, so using a Telnet server under Linux makes your system accessible from just about everywhere. ![]()
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