I am on Ubuntu and using PuTTY to generate SSH keys and connect to the droplet. I can SSH login as root. But not as non-root. This is what i did to SSH login as non-root user:

1. I manually copied and paste the public key to the file under non-root user

2. Did the following command for permission:

   chmod 700 .ssh
   chmod 600 .ssh/authorized_keys
   service ssh restart
   

   This is the error i got when tried to SSH login as non-root:

   Using username "lin-yuan".
   Server refused our key
   lin-yuan@usorgames.com's password:
   

   The following are what i tried to debug:

3. I tried lin-yuan@UF:~$ sshd -t and get this:

   Could not load host key: /etc/ssh/ssh_host_rsa_key
   Could not load host key: /etc/ssh/ssh_host_dsa_key
   Could not load host key: /etc/ssh/ssh_host_ecdsa_key
   Could not load host key: /etc/ssh/ssh_host_ed25519_key
   

4. Then i tried lin-yuan@UF:~$ sudo /usr/sbin/sshd -d and get this:

   debug1: sshd version OpenSSH_7.2, OpenSSL 1.0.2g  1 Mar 2016
   debug1: private host key #0: ssh-rsa SHA256:+LJlY5iA1DGgr8cGZ2NOtZPT9ATq0gHoQ5YZwFq0TJE
   debug1: private host key #1: ssh-dss SHA256:V0ZtT2SCbigpnhFaVRMjmXvo+4JtPUBRnh96L14Aue4
   debug1: private host key #2: ecdsa-sha2-nistp256 SHA256:JoKckvTAm13WGE+3KWxROZc9C0SVf40Gn2cxHP6qDeU
   debug1: private host key #3: ssh-ed25519 SHA256:lxGynCJlUXTjXsq2jeaVrB7YfiPPpRgcrQlyWPwO7Kc
   debug1: rexec_argv[0]='/usr/sbin/sshd'
   debug1: rexec_argv[1]='-d'
   debug1: Set /proc/self/oom_score_adj from 0 to -1000
   debug1: Bind to port 22 on 0.0.0.0.
   Bind to port 22 on 0.0.0.0 failed: Address already in use.
   debug1: Bind to port 22 on ::.
   Bind to port 22 on :: failed: Address already in use.
   Cannot bind any address.
   

   But i still have no clue where might went wrong, can you help me? I attached the content of my /etc/ssh/sshd_config as below just in case if there are some setting that needs to be changed.

   # Package generated configuration file  
   # See the sshd_config(5) manpage for details        
   # What ports, IPs and protocols we listen for   
   Port 22 
   # Use these options to restrict which interfaces/protocols sshd will bind to    
   #ListenAddress ::   
   #ListenAddress 0.0.0.0  
   Protocol 2  
   # HostKeys for protocol version 2   
   HostKey /etc/ssh/ssh_host_rsa_key   
   HostKey /etc/ssh/ssh_host_dsa_key   
   HostKey /etc/ssh/ssh_host_ecdsa_key 
   HostKey /etc/ssh/ssh_host_ed25519_key   
   #Privilege Separation is turned on for security 
   UsePrivilegeSeparation yes      
   # Lifetime and size of ephemeral version 1 server key   
   KeyRegenerationInterval 3600    
   ServerKeyBits 1024      
   # Logging   
   SyslogFacility AUTH 
   LogLevel INFO       
   # Authentication:   
   LoginGraceTime 120  
   PermitRootLogin yes 
   StrictModes yes     
   RSAAuthentication yes   
   PubkeyAuthentication yes    
   #AuthorizedKeysFile %h/.ssh/authorized_keys 
   # Don't read the user's ~/.rhosts and ~/.shosts files   
   IgnoreRhosts yes    
   # For this to work you will also need host keys in /etc/ssh_known_hosts 
   RhostsRSAAuthentication no  
   # similar for protocol version 2    
   HostbasedAuthentication no  
   # Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication   
   #IgnoreUserKnownHosts yes       
   # To enable empty passwords, change to yes (NOT RECOMMENDED)    
   PermitEmptyPasswords no     
   # Change to yes to enable challenge-response passwords (beware issues with  
   # some PAM modules and threads) 
   ChallengeResponseAuthentication no      
   # Change to no to disable tunnelled clear text passwords    
   PasswordAuthentication yes      
   # Kerberos options  
   #KerberosAuthentication no  
   #KerberosGetAFSToken no 
   #KerberosOrLocalPasswd yes  
   #KerberosTicketCleanup yes      
   # GSSAPI options    
   #GSSAPIAuthentication no    
   #GSSAPICleanupCredentials yes       
   X11Forwarding yes   
   X11DisplayOffset 10 
   PrintMotd no    
   PrintLastLog yes    
   TCPKeepAlive yes    
   #UseLogin no        
   #MaxStartups 10:30:60   
   #Banner /etc/issue.net      
   # Allow client to pass locale environment variables 
   AcceptEnv LANG LC_*     
   Subsystem sftp /usr/lib/openssh/sftp-server     
   # Set this to 'yes' to enable PAM authentication, account processing,   
   # and session processing. If this is enabled, PAM authentication will   
   # be allowed through the ChallengeResponseAuthentication and    
   # PasswordAuthentication.  Depending on your PAM configuration, 
   # PAM authentication via ChallengeResponseAuthentication may bypass 
   # the setting of "PermitRootLogin yes   
   # If you just want the PAM account and session checks to run without    
   # PAM authentication, then enable this but set PasswordAuthentication   
   # and ChallengeResponseAuthentication to 'no'.  
   UsePAM yes