use scanner/smb/smb_version

msf auxiliary(smb_version) > set RHOSTS 172.16.21.170
RHOSTS => 172.16.21.170
msf auxiliary(smb_version) > run

[*] 172.16.21.170:445 is running Windows XP Service Pack 0 / 1 (language: Chinese - Traditional) (name:LIXIULI-VCS86VR) (domain:WORKGROUP)
[*] Scanned 1 of 1 hosts (100% complete)
[*] Auxiliary module execution completed

因为只是扫描了一台主机，所以使用的默认线程参数1，如果是对一个大规模的网络进行扫描，可以考虑使用set THREAD 线程数 增加扫描线程的数量以加快扫描速度

扫描的结果保存在metasploit的数据库以便后续使用，可以使用db_hosts命令查看数据库中保存的结果

msf auxiliary(smb_version) > db_hosts -c address,os_flavor
[-] The db_hosts command is DEPRECATED
[-] Use hosts instead

Hosts
=====

address os_flavor
------- ---------
172.16.21.170 XP