I have two keygens, one for github no password login, while the other for the remote server login. When I have generated key as usual:

$ssh-keygen -t rsa

Ask me if overwrite the default keygen (of course not!).

So I make a new keygen file named rsa2, whatever.

However, after the command-line:

$cat ~/.ssh/id_rsa2.pub | ssh -p $PORT $USER@$IP "mkdir -p ~/.ssh && cat >>  ~/.ssh/authorized_keys"

PS: Don’t forget to make the set the authority of both the ~/.ssh/ and the authorized_keys on the remote Server,

$sudo chmod 700 ~/.ssh
$sudo chmod 640 ~/.ssh/authorized_keys

Next time, I still need to enter the password.

When I tried to login with a verbose by enter -v, I found the ssh still read the older keygen, id_rsa.pub.

Finally, I found we need to add this new keygen to make it work. Touch a ‘config’ file in the ~/.ssh, and enter:

Host *
  AddKeysToAgent yes
  IdentityFile ~/.ssh/id_rsa
  IdentityFile ~/.ssh/id_rsa2

That will help to solve this problem.

You can also enter the following in the command-line,

$ssh-add ~/.ssh/id_rsa2

It has the same effect.