Analyzing and Managing Networks
35
will open the
resolv.conf file in the
/etc directory
in my specified graphical
text editor, Leafpad. The file should look something like Figure 3-1.
Figure 3-1: A typical resolv.conf
file in a text editor
As you can see on line 3, my nameserver is set to a local DNS server at
192.168.181.2.
That works fine, but if I want to replace that DNS server with,
say, Google’s public DNS server at 8.8.8.8, I could place the following line in
the
/etc/resolv.conf file to specify the nameserver:
nameserver 8.8.8.8
Then I would just need to save the file. However, you can also achieve the
same result exclusively from the command line by entering the following:
kali >
echo "nameserver 8.8.8.8"> /etc/resolv.conf
This
command echoes the string
nameserver 8.8.8.8
and redirects it (
>
)
to the file
/etc/resolv.conf
, replacing the current content. Your
/etc/resolv.conf
file should now look like Figure 3-2.
Figure 3-2: Changing the resolv.conf
file to specify Google’s DNS server
If
you open the /etc/resolv.conf file now, you should see that it points the
DNS requests to Google’s DNS server rather than your local DNS server.
Your system will now go out to the Google public DNS server to resolve
domain names to IP addresses. This can mean domain names take a little
longer to resolve (probably milliseconds). Therefore,
to maintain speed but
keep the option of using a public server, you might want to retain the local
DNS server in the
resolv.conf file and follow it with a public DNS server. The
operating system queries each DNS server listed
in the order it appears in
/etc/resolv.conf, so the system will only refer to the public DNS server if the
domain name can’t be found in the local DNS server.
N O T E
If you’re using a DHCP address and the DHCP server provides a DNS setting, the
DHCP server will replace the contents of the file when it renews the DHCP address.