It is a good thing to set ssh keys for the remote host. We can login a remote host via public key we have set so that no need to enter password every time we try to connect remote server.

How to set a ssh-key

If you google for a bit , you will find some many tutorials about how to set ssh keys. A good article about that is here.

Still need to enter password even though ssh-key was set?

In some case, though ssh-keys was properly set, we still need enter password as if ssh-key not existed. SSH has a verbose mode , just add the -v option.

The above way seems told nothing, but cat /var/log/secure will give more useful information. In the terminal of remote host, type :

sudo cat /var/log/secure  

we found something as the following:

Apr 19 09:54:19 iZ94z0jz2inZ sshd[5704]: Authentication refused: bad ownership or modes 
for file /home/test/.ssh/authorized_keys

For security reason, the mode of files under .ssh directorys is strictly set. SSH doesn’t like it if your home or ~/.ssh directories or ~./ssh/authorized_keys have group write permissions. Your home directory should be writable only by you, ~/.ssh should be 700, and authorized_keys should be 600.

The following shot is the wrong mode:
we can see that authorized_keys file has writable permissions for group, which is not allowed by ssh:

Change to right mode:

Now you can login you remote host without entering passwd, enjoy!