SSH Login delay

[nmeyers at javalinux.net (nmeyers at javalinux.net)]

On Wed, Feb 16, 2005 at 08:14:43AM -0500, Jerry Feldman wrote:
> On Tuesday 15 February 2005 4:14 pm, David Cass wrote:
> > My server is running Red-Hat 9, and when I access the server via SSH, the
> > server responds immediately with a login request, and after I type in my
> > login id the system responds immediately with "Sent username foo", and
> > then there is a LONG pause (up to 30 seconds) before the system asks for
> > my password.
> >
> > I would be pleased if anyone can shed any light on this.
> In addition to what others have said, is it possible (put probably not 
> proabable) that you are spawning sshd via xinetd rather than running sshd 
> as a daemon.
> 
> I would think that RH9 would set up SSHD as a daemon. 

I took a look at my RH9 box - yes, sshd is running as a daemon.

I encountered a similar delay (using a different authentication) and
it was, as others have suggested, reverse DNS lookup. Some google hits
suggested that trying to disable that through sshd_config doesn't always
work - a bug, apparently - and recommended a different approach that did
indeed solve the problem for me. Create a file called /etc/sysconfig/sshd,
containing the following line:

OPTIONS="-u0"

then restart your ssh daemon. This disables the reverse DNS lookup in
a way that doesn't seem possible through sshd_config.

Nathan