Re: [tlug] Slooooooow down: logs, smartctl, DNS? [SOLVED?]

[Darren Cook <darren@example.com>]

> Basically, it amounted to editing a file called /etc/ssh/sshd_config
> and making two changes.
> 
> One was to add this line to the bottom of the file:
> 
> UseDNS no

I've been following this thread closely as I've also noticed
intermittent slowdowns/lockups. Maybe time I put a caching DNS server on
the LAN gateway machine.

The manual ([1]) says:
    UseDNS  Specifies whether sshd should look up the remote
       host name and check that the resolved host name for the
       remote IP address maps back to the very same IP address.
       The default is yes.

So it is more than just for logging. But what security hole, if any, is
being opened by switching it off? Is the answer different for a server
on a LAN, and one that is listening on a global IP?

Darren

[1]: E.g. http://man-wiki.net/index.php/5:sshd_config