ssh localhost

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@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
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IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
56:73:2d:4b:da:0a:12:f5:02:5f:16:c8:64:4f:90:c9.
Please contact your system administrator.
Add correct host key in /home/hadoop/.ssh/known_hosts to get rid of this message.
Offending ECDSA key in /home/hadoop/.ssh/known_hosts:1
  remove with: ssh-keygen -f "/home/hadoop/.ssh/known_hosts" -R localhost
ECDSA host key for localhost has changed and you have requested strict checking.
Host key verification failed.