Change DNS settings on Linux

If you find that your server's Domain Name Server (DNS) settings are
misconfigured or you prefer to use your own, this article describes how to
change your Linux® server's DNS settings.

If you want to test your site without the test link prior to going live with SSL
or verify that an alias site works prior to DNS changes, you can
Modify your hosts file to override the
DNS for a domain on a specific machine.

Add name servers to the configuration file

On most Linux operating systems, the DNS servers that the system uses for name
resolution are defined in the /etc/resolv.conf file. That file should
contain at least one nameserver line. Each nameserver line defines a DNS
server. The name servers are prioritized in the order the system finds them in
the file. Use the Internet Protocol (IP) addresses of the name servers when
you enter them into the configuration file because the system doesn't know
what to do with domain names until after it knows how to get to the DNS

In some cases, /etc/resolv.conf could be a directly managed file,
populated by the network service (network by using initscripts or
NetworkManager). To directly edit the configuration file, use the
following steps to add the DNS servers:

  1. Open the resolv.conf file with an editor, such as nano, to make the
    necessary changes. If the file doesn't already exist, this command creates it:

    sudo nano /etc/resolv.conf

  2. Add lines for the name servers that you want to use. The following table
    displays which name server IP addresses to use depending on which datacenter
    houses your cloud servers. The "Name server IP address" column shows the
    lines to add to the configuration file:

    Data centerName server IP address
    Hong Kong (HKG)nameserver
    Northern Virginia (IAD)nameserver
    London (LON)nameserver
    Chicago (ORD)nameserver
    Dallas/Fort Worth (DFW)nameserver
    Sydney (SYD)nameserver
    Frankfurt (FRA)nameserver
  3. Save the file.

  4. To ensure that your new settings are working, ping the domain name by
    using the following command:

    ping -c 3

You should see a result similar to the following one:

PING ( 56(84) bytes of data.
64 bytes from icmp_req=1 ttl=249 time=25.3 ms
64 bytes from icmp_req=2 ttl=249 time=25.2 ms
64 bytes from icmp_req=3 ttl=249 time=25.2 ms

--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 25.236/25.292/25.392/0.147 ms

If you receive an unknown host message, double-check the IP addresses that
you set as your DNS servers.

Add the same name servers with IPv6 addresses

If you're using IPv6 on your server, you might need to add the IPv6
addresses of your name servers to the resolv.conf file. You can see if a
DNS server has an IPv6 address by performing the following steps:

  1. Use the following host command to get the domain name of the server
    (substitute your DNS server IP address):

    $ host domain name pointer
  2. Use the domain name you got back in another host lookup:

    $ host has address has IPv6 address 2001:4800:d::1

If an IPv6 address is returned, you can add that as another nameserver
line in the resolv.conf file, as follows:

nameserver 2001:4800:d::1

Then test as previously shown, by using the ping6 command instead of the
regular ping command to force the system to use IPv6.