No new telnet sessions allowed ?

[Al Licause]

Customer has about 61 or 62 people/sessions logged in using telnet and any new sessions simply get no prompt.

This is RHES V4.

tty.max is set to 4096 and the number of psuedo devices in /dev seems to be about 63.

In Tru64unix if this happens, we simply create more psuedo devices with /dev/MAKEDEV. It would appear you can do the same in linux with the MAKEDEV utility giving pty and tty as arguments in seperate commands. This creates several hundred new devices.

But the customer says they still can't telnet....no response. Only if someone logs out, can they start a new session.

So my question is, must the system be rebooted inorder for the kernel to see the new psuedo devices or are there any other parameters that need to be set ?

I don't yet know if there are any errors or other in the messags file, but I've asked the customer to check this.....any other ideas ?

[Ivan Ferreira]

First, as you use RHES V4, a very recent version, you should start by disabling legacy and insecure devices, such telnet and replace it by ssh.

Anyway, check the /etc/xinetd.d/telnet file:

service telnet
{
disable = no
instances = 100
flags = REUSE
socket_type = stream
wait = no
user = root
server = /usr/sbin/in.telnetd
log_on_failure =
log_on_success -= HOST

}

Look at the instances parameter. I think that telnet sessions uses /dev/pts/* files, what is the output of tty in a telnet session?

[Al Licause]

Ivan...thanks yes, we're aware of the ssh and security issues which the customer will address at a later time. They simply wanted to get the system up and in production....unfortunately they didn't test this before going production.

I am having him send me the xinetd.d/telnet file contents but I'm not sure that it has a limit by default.

The tty command does show /dev/pts/x so it is using the system 5 style devices by default.

I was just told that the default for the value of "instances" in /etc/xinetd.d/telnet is 60 even if it is not specified in the file.

I am asking the customer to add the line and set it to some value greater than the max number of telnet users they expect and then restart xinetd. I'll report the results later.

[rick jones]

FWIW the xinetd.conf manpage does say the default is unlimited, but in addition to the xinetd.d/telnet file you may want to check in /etc/xinetd.conf itself since IIRC that can set things which will be "inherited" by the stuff in .d.

[Al Licause]

Thanks again for the information. This is definately one for the personal notes for future use.