How To Find the OS of a Remote Computer - Linux and Windows

Although we're primarily a Windows shop, with the proliferation of virtual appliances, I been working more with the Linux OS (YAY!)  With this comes non-Windows questions, like "What is this host on our domain?"

I've found the easiest way to find the OS running on a remote server is by using NMAP (Network Mapper).  The results may not be 100%, but it gets you pointed in the right direction.

I personally run NMAP from my CentOS 7 box.  To install NMAP, go to the location of the nmap distributions and note the latest rpm. 

https://nmap.org/dist/

Log into your CentOS and run the following command to download and install nmap:

sudo rpm -vhU https://nmap.org/dist/nmap-7.40-1.x86_64.rpm

To find the OS, run the following command:

sudo nmap -O servername

Here's an example of the output.  It's not perfect, but you get a general sense of the OS.  In this case, it was a test ESXi host running 6.5.