Increase the number of telnet sessions allowed

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Q. I am using Fedora Linux and it act as telnet server for our University UNIX lab. We have total 250 computers. At a pick time more than 100 people try to connect server. Only 90 connections are allowed (configured by old admin). Now I want to take this limit to 300 connections or instances. How do I increase the number of telnet sessions allowed?

A. Under Fedora Linux (and old Red Hat Linux or RHEL) xinetd use to control telnet server. The eXtended InterNET Daemon, is an open-source daemon which runs on on many Unix systems and manages Internet-based connectivity. It offers a more secure extension to or version of inetd, the Internet daemon.

xinetd features access control mechanisms, extensive logging capabilities, and the ability to make services available based on time. It can place limits on the number of servers that the system can start, and has deployable defence mechanisms to protect against port scanners, among other things.

You need to edit /etc/xinetd.conf or /etc/xinetd.conf/telnet file and set instances = unlimited:# vi /etc/xinetd.confEdit instances line so that it should read as follows:instances = unlimitedORinstances = 300Restart the xinetd service:# /etc/init.d/xinetd restart


Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

5 comment

  1. Q: when more than 5 users login to linux machine via telnet, commands are respoded very slowely and users sessin disconnect after some time.

  2. On Linux 4 I was able to just “reload” the xinetd service to get the change to work. I had active telnet sessions I didn’t want to get disconnected during a restart. Otherwise, it worked like a charm.

  3. Hi ,

    will you please let me know how to configure the ( or increase the) number of telnet sessions allowed for free BSD version number 3.5.1

    I tried with above mentioned procedure for increasing the number of seesions but i am unable to configure it.It seems the above procedure is for unix/linux operating system.

    please let me know how to configure this in free BSD 3.5.1 (kernel version).

    Thanks in advance


  4. Hello,
    I am totly new to Cent OS. i got help from about internet connection sharing and i did it. its very helpful. but the thing i need to know. i am able to connect to my mail server pop 110 using #telnet 110 and smtp 25. but i could not connect these port through client computer using by windows XP. please provide help regarding this. yes on this server mySQL database is also running i need to make telnet without disturbing this database.

    Please anyone help me out

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