New User Setup on a Debian/Ubuntu Server

This is my process to setup a new user with SSH access on a Debian/Ubuntu server. In this example we will create a new user named USER. Before adding the user, edit /etc/ssh/sshd_config as root and ensure the following configuration settings are present:

PubkeyAuthentication yes
PasswordAuthentication no

# Add this line to the end of /etc/ssh/sshd_config if not already present.
# This line contains a list of users that may login via SSH - in this case,
# root, the user ashn, and our soon to be created user USER.
AllowUsers root ashn USER

Be sure to restart the SSH daemon with systemctl restart sshd for these configuration settings to take effect.

Setting Up a New User

Create the new user with useradd:

$ useradd -m -d /home/USER -s /bin/bash USER

Create the user's .ssh directory and authorized_keys file:

$ mkdir -p /home/USER/.ssh && touch /home/USER/.ssh/authorized_keys

Edit authorized_keys and paste the contents of the user's into the file.

$ vim /home/USER/.ssh/authorized_keys

Set the permissions and ownership of the .ssh directory and authorized_keys file in order to make the SSH daemon happy.

$ chmod 700 /home/USER/.ssh && chmod 600 /home/USER/.ssh/authorized_keys
$ chown -R USER:USER /home/USER/.ssh

Deleting a User

To delete the user and their home directory run:

$ userdel -r USER