Just append -O and -v to a command-line:
nmap -O -v ip-address
Note you need administrative privileges for this on Mac OS X, so there you run it like this:
sudo nmap -O -v ip-address
If you want to scan more than the default 1000 TCP ports, then use the -p- switch:
sudo nmap -O -v -p- ip-address
For more info about the finger printing algorithms used by nmap:
- Chapter 8. Remote OS Detection.
- Remote OS Detection via TCP/IP Fingerprinting.
- Nmap Overview and Demonstration.
–jeroen
via: Usage and Examples.
The Wiert Corner - irregular stream of stuff 