Linux in a Windows World

Telnet Server Configuration

As one of the oldest and most popular remote text-mode login tools available, Telnet is an excellent choice for compatibility—just 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. Telnet’s unencrypted nature, though, is a major drawback. 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 servers are simple and easy to configure in Linux; the worst complication is knowing whether you’re using the inetd or xinetd super server. 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.

Launching a Telnet Server

All major Linux distributions ship with a Telnet server, although many don’t install it by default. Likely package names include telnetd, telnet-server, netkit-telnetd, telnet-bsd, and utelnetd, among others. (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. Although Telnet servers come from several different sources, basic configuration and use is fairly consistent.

Typically, Telnet servers are launched from super servers—usually inetd or xinetd. If you’re not sure which super server your ...