Function: Contains the public part of the host key. This file is writable
 by the system account only and readable by world. 
Creation: Together with the private part of the host key during SSH
 server configuration (if requested). The new key can be created any time
by  a system manager running the key generation utility, SSH_KEYGEN, which
creates  both keys).
Scope: Systemwide
Use: Server host identification. Required on the SSH client in the [username.SSH2.KNOWNHOSTS] directory in order to use
any authentication method. Also required on the server for host-based authentication.