Check and change the DNS Resolvers of your Linux Server uses

Below is a step-by-step guide on how to locate your DNS Server settings on a Linux server.

Systemd resolve hierarchy.

This article assumes that /etc/nsswitch.conf is configured to refer to /etc/resolv.conf, which is the case by default on most distributions. This is defined in the hosts: line like the following example of an AlmaLinux Server:

hosts:      files mdns4_minimal [NOTFOUND=return] dns myhostname

SSH into your server as the root user.
Edit the /etc/resolv.conf file using a tool such as vim or nano. In the below example, it is pointing at Indigo Legacy Resolvers, and needs to be changed.
```
nameserver 114.141.193.250
nameserver 114.141.200.250
```
Update it to point to the correct servers, and then save the file.
```
nameserver 221.121.130.3
nameserver 221.121.134.9
```
Your DNS resolvers will now be updated. If this is CentOS, you should have a quick look in your /etc/sysconfig/network-scripts/ifcfg-* files and see if they have DNS1= and DNS2= lines. If they do, you will need to also update those lines to the new Resolvers shown above.
```
DEVICE=enp1s0
TYPE=Ethernet
BOOTPROTO=none
ONBOOT=yes
PREFIX=24
IPADDR=10.0.1.27
GATEWAY=10.0.1.1
DNS1= 221.121.130.3
DNS2=221.121.134.9
```
Barring edge cases, you should now be correctly configured.

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Check and change the DNS Resolvers of your Linux Server uses