Answer by Govind Karamta for Copy ssh keys from one server to another server

You can try it like this

cat ~/.ssh/id_rsa.pub | ssh <user>@<hostname> 'cat >> .ssh/authorized_keys && echo "Key copied"' 

Note that if the folder .ssh does not already exist, the above command will fail. In addition, it might be better when creating the file to set a minimum possible permission (basically read-write for owner only). Here is a more advanced command:

cat ~/.ssh/id_rsa.pub | ssh <user>@<hostname> 'umask 0077; mkdir -p .ssh; cat >> .ssh/authorized_keys && echo "Key copied"'

For more light on this problem you have to get to this website : SSH Host Key Change Error