This may be because
StrictHostKeyChecking option is set to
ask. It may not be set explicitly,
ask is the default value.
man 5 ssh_config:
If this flag is set to
ssh(1) will never automatically add host keys to the
~/.ssh/known_hosts file, and refuses to connect to hosts whose host key has changed. This provides maximum protection against trojan horse attacks, though it can be annoying when the
/etc/ssh/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
ask. The default is
Looks like you would like to set the option to
/etc/ssh/ssh_config the line would be:
Or you can override the option during
scp invocation by passing
-o StrictHostKeyChecking=no to the tool, e.g:
ssh -o StrictHostKeyChecking=no root@host "command"
scp -o StrictHostKeyChecking=no /local/file root@host:"$directory"/
Note there is also
VerifyHostKeyDNS option with the default value
ask. Refer to the manual. If you need to change it, the solution is similar.