Testing DNS using the default server:

To test whether the DNS server is working properly, we could use the "dig" utility that resolves a hostname and returns its IP address, along with some other information: 


If we don't mention any DNS server, the default one - "" - in "/etc/revolv.conf" will be used:

Using "nslookup" To test the DNS server:

We could also use the nslookup tool as below to test our DNS server:

If we omit the "dns-server", the default one in the "/etc/revolv.conf" file will be used.

The "host" utility:

The "host" utility is a simple tool that could be used instead of "dig" to get the IP address of a host as we can see below:


Using the default DNS from the "/etc/resolv.conf" file:

We could also make the request to a specific DNS server - - as below:


DNS configuration files:


The file contains a mapping between IP addresses and URLs as we can see below:

If we add for example a line with " google.com", it will keep us from accessing "google.com" since it will be mapped to the wrong address "".

Before the system looks up an address via DNS, it checks the "/etc/hosts" file first as stated in the "/etc/nsswitch.conf" file.

"/etc/nsswitch.conf" :

One of the roles of the "/etc/nsswitch.conf " file is that it specifies the order in which the system does the DNS lookup:

The above line for example, means that the system tries to resolve a DNS name by first  looking in the "/etc/hosts" file, before querying the DNS server mentioned in the "/etc/revolv.conf" file .


The "/etc/revolv.conf" file contains a list of name servers. We don't have to edit the file manually, it is populated automatically by the "systemd-resolve" service.


If we change the DNS configuration files, we would need to restart the DNS server using the below command:

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