General
cancel
Showing results for 
Search instead for 
Did you mean: 

Max telnet sessions Redhat AS2.1

Geoff Dunk_1
Occasional Advisor

Max telnet sessions Redhat AS2.1

I am having trouble with telent sessions failing at about 120 when connecting to our RH AS2.1. We are performance testing our machines and I am getting the error:
xinetd[1037]: telnet: fork failed: Cannot allocate memory (errno = 12)
I need to connect to the machine with around 2000 sessions. Can anyone out there help please?
12 REPLIES
Geoff Dunk_1
Occasional Advisor

Re: Max telnet sessions Redhat AS2.1

I have tried the CONFIG_UNIX98_PTY_COUNT option, but this is an invalid parameter under AS2.1.
Ivajlo Yanakiev
Respected Contributor

Re: Max telnet sessions Redhat AS2.1

Offhand what are the limits for the system? (ulimit -Ha and ulimit -Sa)

/proc/sys/fs/file-nr and inode-nr values What is swap usage ?
#free

It can be lack of indos for FD
or low memory


Ivajlo Yanakiev
Respected Contributor

Re: Max telnet sessions Redhat AS2.1

Also you cant install glance to see waht kernel parm is 100 % used.

Geoff Dunk_1
Occasional Advisor

Re: Max telnet sessions Redhat AS2.1

I have these values on my system, and at the time of error, there was no swapping going on.

inode-nr
132772 132303

file-nr
374 32 262144

core file size (blocks) 0
data seg size (kbytes) unlimited
file size (blocks) unlimited
max locked memory (kbytes) unlimited
max memory size (kbytes) unlimited
open files 1024
pipe size (512 bytes) 8
stack size (kbytes) 8192
cpu time (seconds) unlimited
max user processes 14335
virtual memory (kbytes) unlimited

Any good ideas?
Ivajlo Yanakiev
Respected Contributor

Re: Max telnet sessions Redhat AS2.1

what kind of kernel you use ?
#uname -a



Steven E. Protter
Exalted Contributor

Re: Max telnet sessions Redhat AS2.1

It may be other problems. You may not have the ability to create more processes or inadequate swap memory.

The fact it happens at 120 users does point to a limit in the kernel. The error message itself brings up the possibility of other issues.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
Geoff Dunk_1
Occasional Advisor

Re: Max telnet sessions Redhat AS2.1

Steven
Any pointers the direction or area I need to look?
Ivajlo Yanakiev
Respected Contributor

Re: Max telnet sessions Redhat AS2.1

I have some idea.
do not use xinetd for fork telnet
start telnetd daemon and test again.

Pls give me your kernel version
#uname -a
Geoff Dunk_1
Occasional Advisor

Re: Max telnet sessions Redhat AS2.1

kernel version is:
2.4.9-e.12smp

Re: Max telnet sessions Redhat AS2.1

Hi Geoff,

maybe you limit resources in /etc/xinet.conf
(instances = numer of active services for a particular service).

bye
Matthias
Geoff Dunk_1
Occasional Advisor

Re: Max telnet sessions Redhat AS2.1

Thanks for that Matthias, but my xinet.d limits are set to unlimited. I can't help but think the problem maybe in some other area, maybe something to do with the amount of connections/threads to the box and telenet just happens to be the process we are using most off.
Karsten Breivik_1
Frequent Advisor

Re: Max telnet sessions Redhat AS2.1

This could be a little far fetched, but starting a new telnet session can sometimes take a long time, sometimes ~30 sec to get a login prompt. This is often caused by the server wanting to do a reverse DNS lookup to find out who is connecting. I found this tip online:

If you are running DNS, check named and resolv.conf to find out how IP adresses are resolved.

If you aren't running a DNS which can do a reverse name-lookup to the clients, you can fix this just by listing all the machines in /etc/hosts. Note that you don't have to be accurate about the names: I often use the ip adress with "_" substituted for the "."'s, like "host_192_168_2_3" and so on. A simple script:

#!/bin/ksh
x=1
while [ $x -lt 255 ]
do
echo "192.168.0.$x host_$x"
x=$((x + 1 ))
done >> /etc/hosts

Change the script to fit your subnets. This will append the /etc/hosts file and make reverse resolving fast on a network on which the DNS is unable to reverse lookup the clients.

poi