Setup an Ubuntu server may be done in multiple ways but I'd like to share with you the simple and quick steps I usually do when I get a raw machine in my hands.
Setup the SSH connection
Let's start with the basics, you need to connect to your server instance. Usually, during the creation of your container or virtual machine you have the opportunity to inject your SSH public key into it. If it's the case, DO IT, then SSH will be enabled by default and you can connect without using a password.
If it's not the case, you can copy your public SSH key into ~/.ssh/authorized_keys and enable the ssh service.
Then you can connect to the root user:
ssh root@<server_ip> -i ~/.ssh/id_pk # i usually use -i option to select the ssh key as i have multiple ones
Hopefully, your first step on the machine is to update the server packages:
apt update apt upgrade
Prepare a non-privileged user
Add a non-privileged user (name "demo" for this tutorial):
Optional: As we're on Ubuntu the sudo package is available, so let's use this feature and give some privileges to our user (this step may not be recommended in terms of security).
# we add the user to the sudoers usermod -aG sudo demo
Copy the authorized_keys to your demo user (so you can still ssh on it):
rsync --archive --chown=demo:demo ~/.ssh /home/demo
Note: it is the same thing as:
mkdir /home/worker/.ssh cp ~/.ssh/authorized_keys /home/worker/.ssh/authorized_keys chown worker:worker /home/worker/.ssh/authorized_keys
At this point, you can test connecting with demo user.
Let's harden a bit the server
You should disable root login:
vi /etc/ssh/sshd_config # edit / add those lines PermitRootLogin no # if you never lose your SSH keys PasswordAuthentication no
You can also configure the ufw package which is a simple firewall.
Important note: make sure you allow SSH ports, otherwise, you will be locked out.
ufw app list ufw allow 22 # or something else depending on your default ssh port ufw allow http ufw allow https # for a web server ufw enable ufw status
And voilà! These are some quick steps but you have already a good setup to start working. Please share any improvements you find to this guide (remember I want to keep it short) and I'll update the page.