I'm running Metasploit in archlinux and when I execute msf> db_nmap -hIt'll return an error: The nmap executable could not be foundNow, I know I am probably missing a binary or something, but how did I end up missing it? I installed ruby1.9 and metasploit-git from the AUR. 
Can't find nmap executable in Metasploit
arch linux;metasploit