Re: Problem running Nmap

[Ron <ron () skullsecurity net>]

Hi Neminath,

Are you specifying the host with a numeric ip address (eg, 12.34.56.78) 
or a name (server.mydomain.x)? I'm assuming the first, baesd on your 
question.

The first problem seems to be that the system you're running it from 
doesn't have the normal DNS file, /etc/resolv.conf. You can create a 
default one with the following command:

  echo "nameserver 4.2.2.1" >> /etc/resolv.conf

That'll set you up with a solid default nameserver. The alternative is 
to specify it on nmap's commandline:

  nmap --dns-servers 4.2.2.1 x.x.x.x

That'll do it without touching the system's configuration.

The other issue seems to be that the server you're scanning isn't 
returning pings, or is offline entirely. If it isn't returning pings and 
you know it's operational, try:

  nmap -PN x.x.x.x
or
  nmap -P0 x.x.x.x
(that's a zero after the 'P')

If that still returns no results, then the target isn't up or you're 
being blocked by something else.

Two more notes:
a) You may need to run these with root privileges, try doing a "su" 
first, or putting a "sudo" in front of the commands.
b) You're running an old version of nmap, you may want to update.

Hope that helps!

Ron

Neminath wrote:
> I m new to Nmap and to linux rather
> have the following problem running Nmap scanner
>
>
> nmap -O x.x.x.x
> when i run the above command i get the following (infact for all the
> commands)
>
> Starting Nmap 4.20 ( http://insecure.org ) at 2008-07-06 11:46 IST
> mass_dns: warning: Unable to open /etc/resolv.conf. Try using --system-dns
> or specify valid servers with --dns-servers
> mass_dns: warning: Unable to determine any DNS servers. Reverse DNS is
> disabled. Try using --system-dns or specify valid servers with --dns_servers
> Note: Host seems down. If it is really up, but blocking our ping probes, try
> -P0
> Nmap finished: 1 IP address (0 hosts up) scanned in 0.171 seconds
>
> whats this message is all about how do i resolve it .
>
> Regards
> Neminath


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