mass_dns: warning: Unable to determine any DNS servers. Reverse DNS is disabled

Question

I'm using UBUNTU 14.04 as virtual machine on Windows using VMWARE , after logging I installed nmap but after trying to run

nmap -sP 10.42.0.0

I get the following message

mass_dns: warning: Unable to determine any DNS servers. Reverse DNS is disabled. Try using --system-dns or specify valid servers with --dns-servers

I'm using

Nmap version 6.40 ( http://nmap.org ) Platform: x86_64-pc-linux-gnu

any hints ?

Solution

I'm assuming that you are specifying the host with a ip address (eg, x.x.x.x)

It seems that the system you're running it from doesn't have a normal DNS file, /etc/resolv.conf.
So, You can create a default nameserver with any IP (e.g. 6.7.8.9) using following command:

# echo "nameserver 6.7.8.9" >> /etc/resolv.conf

This will set up a default nameserver.

Alternately you can specify it on nmap command without touching the system's configuration.

# nmap --dns-servers 6.7.8.9  x.x.x.x

Comments

[bonsaiviking]

Please clarify what you mean by "on windows." What DNS servers do you expect to be configured? Include diagnostic output regarding your DNS setup: cat /etc/resolv.conf

[Incnis Mrsi]

@Frankenstein: Can anything (but itself and the host system) be pinged from your virtual machine by IP?

[The Beast]

@IncnisMrsi no i can't ping anything

[Incnis Mrsi]

@Frankenstein: Then it’s a network connectivity problem, and DNS is irrelevant. Which efforts did you apply to route or bridge your virtual machine to the outside world? By the way, Ī̲ start to think it’s a Windows question.

[The Beast]

@IncnisMrsi well i don't know , i haven't made any efforts to route or bridge my virtual machine to the outside world because i was thinking that it must be done automatically , please if you know to how to setup up the it will be much helpfull for me