First thing to do after creating a new VPS server: setup deploy user and enable SSH-key authentication only

1) Create on the remote server a deploy user:

# on the server, as a root user

$ adduser deploy
$ adduser deploy sudo

2) Make sure that you can login to the server as a deploy user without password prompt:

It assumes that you have ssh keypair already (~/.ssh/id_rsa and ~/.ssh/id_rsa.pub) on your desktop.

# on the desktop

$ ssh-add
$ ssh-copy-id deploy@deploy_server_ip

# Now try to login to the server as deploy user:
$ ssh deploy@deploy_server_ip

If it didn’t work, and you get message like Permission denied (publickey), it seems like password authentication disabled by default on your server (which is a good thing actually). Login to the server as a root again, then login to deploy user ($ su - deploy) and add your .pub key to the deploy’s ~/.ssh/authorized_keys file:

$ mkdir -p ~/.ssh && chmod 700 ~/.ssh
$ echo your_public_key_string_value >> ~/.ssh/authorized_keys && chmod 644 ~/.ssh/authorized_keys

If all went fine, you should be able to login without password ($ ssh deploy@deploy_server_ip).

Bonus: disable password login authentication

Some VPS providers don’t have an option to allow provide a custom public SSH key for the root user’s authentication while creating a new VPS server. In this case, you’ll get automatically generated password (for root user) after VPS will be created, which then can be used to login to the server. But, using password authentication isn’t a good practice and can leave security vulnerabilities, such as brute force attack. It’s better to disable password auth and use only SSH key authentication.

1) Copy your public SSH key to the server’s root user using ssh-copy-id tool:

$ ssh-copy-id root@deploy_server_ip

Example:

$ ssh-copy-id root@5.180.150.210
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/bob/.ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@5.180.150.210's password:

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'root@5.180.150.210'"
and check to make sure that only the key(s) you wanted were added.

If all went fine, you’ll be able to login to the server without a password prompt. Do it and:

2) On the server (as a root user), open /etc/ssh/sshd_config file (you can use nano editor),

This is an important step, before process it MAKE SURE THAT you can sucessfully login to the server using SSH key, (not password). Otherwise you can lose access to your server.

and navigate to PasswordAuthentication line. Make sure that it’s not comment-out (not starts with #), and set value to no:

PasswordAuthentication no

Then save the file.

3) Restart sshd to apply new settings: $ service ssh restart. All done!