topic Re: it is very slow to get command prompt after entering the password when logging thru putty (ssh) in Operating System - Linux

it is very slow to get command prompt after entering the password when logging thru putty (ssh)

senthil_kumar_1 — Tue, 04 Aug 2009 17:01:15 GMT

Hi All,

In of my Suse linux server, it is very slow to get command prompt after entering the password when logging thru putty (ssh).

How to solve this?

Re: it is very slow to get command prompt after entering the password when logging thru putty (ssh)

Steven Schweda — Tue, 04 Aug 2009 17:29:39 GMT

Is this the same (reverse-) DNS problem as
in:

http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1358233

?

A Forum search for keywords like
ssh slow
might find some of the dozens of similar, old
threads.

Re: it is very slow to get command prompt after entering the password when logging thru putty (ssh)

senthil_kumar_1 — Wed, 05 Aug 2009 11:56:06 GMT

But i am able to resolve the name and ip thru DNS running in that particular Linux server.

Re: it is very slow to get command prompt after entering the password when logging thru putty (ssh)

Ivan Ferreira — Wed, 05 Aug 2009 12:47:40 GMT

To identify if the problem is reverse dns lookups, you could configure the following option in sshd_config and reload the service:

UseDNS no

Re: it is very slow to get command prompt after entering the password when logging thru putty (ssh)

Steven Schweda — Wed, 05 Aug 2009 13:29:52 GMT

> But i am able to resolve the name and ip
> thru DNS running in that particular Linux
> server.

Which "name and ip" can you resolve where?
Evidence?

Re: it is very slow to get command prompt after entering the password when logging thru putty (ssh)

Matti_Kurkela — Wed, 05 Aug 2009 14:08:38 GMT

Can you identify where the slowness happens? Does it happen before /etc/profile starts, or somewhere within /etc/profile or your personal login script?
Add some commands like:

echo "in the beginning of /etc/profile"

to various locations in the login scripts, then try to locate the point where the system spends a lot of time.

One common reason for slow logins is a large wtmp file (/var/log/wtmp in most Linuxes). This usually affects all logins, not only SSH logins. In this case, the slowness usually happens before /etc/profile starts executing.

The wtmp file records all login/logout events. The system must search through it to find & display the last login times. The bigger the file is, the more time the login procedure takes.

RedHat systems have a cron job that periodically truncates the wtmp file (using logrotate to archive a few old versions). This prevents it from ever getting too big. You should check if SuSE has ready-made scripts or cron jobs to manage the wtmp file, and consider enabling them. If there is nothing, write your own.

The simplest script for truncating the wtmp file would be:

#!/bin/sh

# backup the old wtmp file
cp /var/log/wtmp /var/log/wtmp.old
# truncate the wtmp file
> /var/log/wtmp

MK

Re: it is very slow to get command prompt after entering the password when logging thru putty (ssh)

Stephen P. Schaefer — Wed, 05 Aug 2009 23:36:19 GMT

In addition to the other suggestions, check whether ssh is having trouble running xauth - and don't tunnel X if you don't need to.