Update&Install
sudo apt update && sudo apt upgradesudo apt install openssh-server
Check status & Enable SSH
sudo systemctl status sshsudo systemctl enable --now ssh
Check if SSH is enabled to start with the system
sudo systemctl is-enabled ssh
Allow SSH in Firewall
sudo ufw allow ssh
Connect to the server using the default port
ssh username@ip.address
Change the default SSH port
The new port must be located above port 1024
First, we will allow the new port in the firewall
sudo ufw allow 1234/tcp
Then we have to edit the SSH configuration file to set the new port we want to use.
sudo nano /etc/ssh/sshd_config
We will see this:
The last line that says "#Port 22" is the one that we want to edit by removing the "#" and changing the number from 22 to 1234
Then, we have to restart the SSH service to take into account the new port
sudo systemctl restart ssh
Connect to the server using the default port
ssh username@domain.name -p 1234
Setup SSH keys
Before we create a key, we'll ensure we don't have one already:
ls -al ~/.ssh
The existing keys should appear with the names "id_rsa" and "id_rsa.pub"
If we forgot to verify if we have them already and create new ones directly:
ssh-keygen
it will ask where we want to save them:
"Enter file in which to save the key (/home/benjamin/.ssh/id_rsa):"
We can press "Enter" to save on the default location, and we already have keys it asks if we want to overwrite them or not:
"Overwrite (y/n)?"
Copy the public key to the Host/Server
ssh-copy-id username@domain.name
With a differentport than the default one (22), the port must be specified before the username/domain if not, an error will be displayed:
"/usr/bin/ssh-copy-id: ERROR: Too many arguments. Expecting a target hostname, got:...
So the correct argument shuld be:
ssh-copy-id -p 1234 username@domain.name
Check IP of server
1- ip a
OR
2- ifconfig (requires apt install net-tools)