Change DNS settings on Linux
You might need to change your server’s DNS settings, either because you find that they are misconfigured or because you want to use your own. This article describes how to change your server’s DNS settings.
Add name servers to the configuration file
On Linux, 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 IP addresses of the name servers when entering
them, because the system won’t know what to do with domain names until
after it knows how to get to the DNS servers.
Open the resolv.conf file with an editor, such as
nano, to make the necessary changes (if it doesn’t exist already, this command creates the file):
sudo nano /etc/resolv.conf
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 center Name server IP address Hong Kong (HKG) nameserver 126.96.36.199
Northern Virginia (IAD) nameserver 188.8.131.52
London (LON) nameserver 184.108.40.206
Chicago (ORD) nameserver 220.127.116.11
Dallas/Fort Worth (DFW) nameserver 18.104.22.168
Sydney (SYD) nameserver 22.214.171.124
Save the file.
To ensure that your new settings are working,
pingthe domain name:
ping -c 3 rackspace.com
You should see a result similar to the following one:
PING rackspace.com (126.96.36.199) 56(84) bytes of data. 64 bytes from 188.8.131.52: icmp_req=1 ttl=249 time=25.3 ms 64 bytes from 184.108.40.206: icmp_req=2 ttl=249 time=25.2 ms 64 bytes from 220.127.116.11: icmp_req=3 ttl=249 time=25.2 ms --- rackspace.com 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 same 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:
hostto get the name of the server:
$ host 18.104.22.168 240.128.3.72.in-addr.arpa domain name pointer cachens1.dfw1.rackspace.com.
Use the domain name you got back in another
$ host cachens1.dfw1.rackspace.com cachens1.dfw1.rackspace.com has address 22.214.171.124 cachens1.dfw1.rackspace.com has IPv6 address 2001:4800:d::1
If an IPv6 address is returned, you can add that as another
line in the resolv.conf file, as follows:
Then test as previously shown, by using the
ping6 command instead of the
ping command to force the system to use IPv6.
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