Increasing the number of telnet sessions

  • 3000932
  • 10-Oct-2006
  • 09-Oct-2012

Environment

Novell SUSE Linux Enterprise Server 10
Novell SUSE Linux Enterprise Server 9
Novell Open Enterprise Server (Linux based)
Novell Linux Small Business Suite

Situation

Users are connected to the telnet service but no new connections are accepted by the telnet service. For instance, users trying to connect receive an ERROR: Connection closed by foreign host.

Resolution

Access to the telnet service is mediated by xinetd,the extended Internet services daemon which is configured (in /etc/xinetd.conf) to accept a maximum of 30 connections to a service by default.
To change this for the telnet service only, proceed as follows:
 
1.  Open the file /etc/xinetd.d/telnet in an editor. In the curly braces delimited block for "service telnet", add a line specifying the desired maximum number of connections, e.g.
 
instances = 100
 
or
 
instances = unlimited
 
2.  Activate the new setting through
 
rcxinetd restart

Additional Information

Security considerations

The telnet service does not provide for confidentiality of any part of the connection (including authentication credentials like passwords) and should thus only be used in network environments which are trusted completely.


In network environments which should not completely trusted, for example ones connected to the Internet, a remote connection protocol which provides for confidentiality of the connection and for peer authentication should be used instead of telnet. The SSH (secure shell) protocol is often used as a more secure replacement for the telnet protocol.

On Linux systems, the "openssh" package provides both a client and a server for the SSH service. On Microsoft Windows systems, several SSH client implementations exist, for example PuTTY which is free software.

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