SSH "Are you sure you want to continue connecting"表示をなくす

2016 Dec. 10. より

sshクライアント側の /etc/ssh/ssh_config のStrictHostKeyChecking設定をnoにする。(ask/yes/noを設定できる)
  StrictHostKeyChecking no

$ man ssh_config
If this flag is set to ``yes'', ssh(1) will never automatically
add host keys to the ~/.ssh/known_hosts file, and refuses to con-
nect to hosts whose host key has changed. This provides maximum
protection against trojan horse attacks, though it can be annoy-
ing when the /etc/ssh_known_hosts file is poorly maintained or
when connections to new hosts are frequently made. This option
forces the user to manually add all new hosts. If this flag is
set to ``no'', ssh will automatically add new host keys to the
user known hosts files. If this flag is set to ``ask'', new host
keys will be added to the user known host files only after the
user has confirmed that is what they really want to do, and ssh
will refuse to connect to hosts whose host key has changed. The
host keys of known hosts will be verified automatically in all
cases. The argument must be ``yes'', ``no'', or ``ask''. The
default is ``ask''.