I was looking into: 'last -d' command.
-d: For non-local logins, Linux stores not only the host name of the remote host but its IP number as well. This option translates the IP number back into a hostname.
At first, I was looking at similar questions, This one in particular: 'last -d' is REALLY slow
Before I updated my hosts file and added: 0.0.0.0 localhost I received less hostnames and more IP addresses. So that means Linux stores the hostnames somewhere in the OS, If that's the case, is there any way of reaching the hostnames without the command