How To Fix Telnet Rejection Error of Name or Service Not Known: Illegal Seek

We all know that telnet is a good remote access protocol in the old days. Now, we prefer SSH protocol because SSH is a secure protocol, i.e. it’s not easy to hack.

However, for some reasons, telnet server still installed for some (Microsoft Windows) users who

desperately need remote access facility. (Maybe telnet server will go into history when Windows start to bundle Putty or its own SSH client).

So, this is what happen here, that we have to install and enable the insecure telnet server on all Red Hat Enterprise Linux servers, for obvious reason.

Problem happen today when one user reported that he cannot telnet to the server, with an rejection error message that said “GetAddrInfo: <hostname>: Success. Name or service not known: Illegal seek” (as seen in the following screenshot taken when I telnet to localhost in a SSH session):

Linux telnet server rejected client connection with error message saying Name or service not known: Illegal seek.

Linux telnet server rejected client connection with error message saying Name or service not known: Illegal seek.

How to fix this so-called “Name or service not known: Illegal seek” error (replied by the telnet daemon)?

Well, I guess this has something to do with DNS resolution. It was working fine until we changed the Linux hostname on yesterday. The hostname is not registered to DNS servers that defined in /etc/resolv.conf file and there is no hostname-to-IP mapping in /etc/hosts file as well.

So, to try out the possible solution, I add in hostname-to-IP mapping in /etc/hosts file, and it works:

192.168.20.21      WalkerNews      WalkerNews.net

[ assuming the hostname is WalkerNews and its IP address is 192.168.20.21]

I am not sure (because I haven’t tried) the problem will be fixed, if I remove the hostname-IP mapping in /etc/hosts and register the hostname-IP to DNS servers that defined in /etc/resolv.conf file. (I bet this will work, too).