As you know Mick Genie ever post on how to set RSA key from Linux PC with URL below.
Create RSA key login for remote login
At the same time, I am being requested by @thebosscat as well for the step.
1. download the puTTYgen from URL below.
2. Run it.
3. Generate the key by mouse over from the red box as above.
4. Set the “Key passphrase” which same like password and copy the public key to your Linux box with file /root/.ssh/authorized_keys.
5. Click on the “Save private key” and save it with .ppk format.
6. Try to load ppk file with your pageant with your password and try to login without need a password.