Enabling Linux telnet

This has to be one of the more common support calls that I get. The telnet daemon is no longer usually installed by default, so people are surprised when their newly installed Linux system won't answer telnets. By the way, I am always careful to explain why telnet isn't there anymore; that they probably should be thinking about ssh. But sometimes there are perfectly reasonable reasons: it's only going to be used for a few internal users, there's no path from the outside world, or their firewall is going to tightly control access. I'd still rather see them use ssh, but if they understand its weaknesses and still want to go ahead, so be it. The first task is to install telnetd. That's the Telnet Daemon that will respond to connection requests from telnet clients. The "telnet" client is installed by default; the telntd daemon is not. If you have a system that is connected to the internet and that has a package manager like up2date, yum or apt-get, you can use that to load this. For example, on a RedHat system, you might do "up2date telnetd" and that would go fetch the appropriate rpm, download it and install it. You still need to get it running (see below) but it's now installed. If you don't have that ability, you need to find the software on your CD's. I'll lead you through an example from a RedHat 9 install. We have to start by putting one of the CD's into the machine. I happen to know that what we want is on CD 3 for RedHat 9, but we're going to pretend that I have forgotten that, so I'll first insert CD 2. Your system may mount the CD automatically. Give it a second, and type "mount". If you see /dev/cdrom in one of the output lines, you can proceed to the next step. If not, you need to mount it manually. For RedHat 9, "mount -r /dev/cdrom /mnt" will work. Now you need to find the rpm that has telnetd. This command will search the appropriate place: ls /mnt/RedHat/RPMS | grep telnet If you don't have RedHat 9, you are going to have to search around for the proper drectory yourself. You can "cd /mnt" and do "ls" and continue until you find what you want. Remember, you are only looking for rpm's if you are using an rpm based system. You need to know what your OS uses. If you can't find anything that looks like telnet (and you won't on CD 2 of RedHat 9), you have to move on to the next CD. If you have cd'd into the mounted directory, you have to cd off that before you can unmount and eject the cd. If not, you'll get "device is busy" and won't be able to remove the cd. In our sample case, we'll do: cd / umount /dev/cdrom I could have also done: cd / eject cdrom Now mount the next CD and repeat your search. On RedHat 9, the grep will turn up something like "telnet-server-0.17-20.i386.rpm". I don't remember the exact numbers from the cd - the important thing is that it's "telnet-server". However, on other systems, it may not be so obvious. For example, from a RedHat ES system: # rpm -q --whatprovides `which telnetd` krb5-workstation-1.2.7-44 chkconfig telnetd on Confirm that telnet now works by "telnet localhost" or "telnet 127.0.0.1". However, if you installed the RedHat firewall, telnet won't be accepting outside connections, not even from your LAN. For RedHat, you can correct that by running "setup", choosing "Firewall Configuration", select "Customize", and "Allow Incoming Telnet". Other systems have other methods for enabling telnet. Most likely, they use APLawrence.com Add to document.write("Del.icio.us") | Yahoo! My Web A.P. Lawrence provides SCO Unix and Linux consulting services http://www.pcunix.com