SSH login takes 1-2 minutes

kenneho · 01-05-2009, 08:34 AM

Hi.

At least one of my servers is hanging quite a bit when logging in (via SSH). After typing in a username and password, it takes 1-2 minutes before I'm logged in.

The server is a RHEL 5.1 box running on Vmware ESX.

I've noticed that running "hostname -s" takes approximately 5 seconds to complete. If this is a symptom of a DNS-problem than maybe this may explain why login takes so long. But I'm not quite sure where to begin debugging. Does anyone have a tip on what may be causing this?

Regards,
kenneho

colucix · 01-05-2009, 08:41 AM

You can start by using the verbose option of ssh. Use one of the following

Code:

ssh -v user@host
ssh -vv user@host
ssh -vvv user@host

to get an increased level of debugging output. In this way you can see exactly where the ssh command hangs.

TB0ne · 01-05-2009, 08:44 AM

Quote:

Originally Posted by kenneho

Hi.
At least one of my servers is hanging quite a bit when logging in (via SSH). After typing in a username and password, it takes 1-2 minutes before I'm logged in.

The server is a RHEL 5.1 box running on Vmware ESX.

I've noticed that running "hostname -s" takes approximately 5 seconds to complete. If this is a symptom of a DNS-problem than maybe this may explain why login takes so long. But I'm not quite sure where to begin debugging. Does anyone have a tip on what may be causing this?

It does sound like a DNS issue. I'd check to make sure that the DNS servers you've got specified in /etc/resolv.conf are correct. Also, you might want to try to add your server (or make sure it's there), to the /etc/hosts file.

There are some gotchas with RHEL5 on VMware...time drift is one of them, and I know there's a patch specifically to address that on VMware, that you don't need for a 'real' server. Might want to call RedHat and see if there's something out there for it...

kenneho · 01-05-2009, 09:21 AM

Quote:

Originally Posted by TB0ne

It does sound like a DNS issue. I'd check to make sure that the DNS servers you've got specified in /etc/resolv.conf are correct. Also, you might want to try to add your server (or make sure it's there), to the /etc/hosts file.

There are some gotchas with RHEL5 on VMware...time drift is one of them, and I know there's a patch specifically to address that on VMware, that you don't need for a 'real' server. Might want to call RedHat and see if there's something out there for it...

I think you're right: I've lost connection with one of the DNS-servers. After removing it from /etc/resolv.conf everything is back to normal. Thanks for your help (both you and colucix).

TB0ne · 01-05-2009, 09:40 AM

Quote:

Originally Posted by kenneho

I think you're right: I've lost connection with one of the DNS-servers. After removing it from /etc/resolv.conf everything is back to normal. Thanks for your help (both you and colucix).

No problem....glad to have helped.