You have compromised a server on a network and successfully opened a shell. You aimed to identify all
operating systems running on the network. However, as you attempt to fingerprint all machines in the networkusing the nmap syntax below, it is not going through.
invictus@victim_server:~$ nmap -T4 -O 10.10.0.0/24
TCP/IP fingerprinting (for OS scan) xxxxxxx xxxxxx xxxxxxxxx.
QUITTING!
What seems to be wrong?

A.
OS Scan requires root privileges.

B.
The nmap syntax is wrong.

C.
This is a common behavior for a corrupted nmap application.

D.
The outgoing TCP/IP fingerprinting is blocked by the host firewall.

Explanation:
You requested a scan type which requires root privileges.
http://askubuntu.com/questions/433062/using-nmap-for-information-regarding-web-host