cj-cloud-init.yml

# This config was written for Ubuntu 22.04
# If you are using a more recent version, see the comments of this gist for fixes
#cloud-config
users:
  - name: cj
    ssh_authorized_keys:
      - "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAINBlfqermlV44zAU+iTCa5im5O0QWXid6sHqh2Z4L1Cm cj@null.computer"
    sudo: ALL=(ALL:ALL) ALL
    groups: sudo
    shell: /bin/bash
chpasswd:
  expire: true
  users:
    - name: cj
      password: changeme
      type: text
runcmd:
  - sed -i '/PermitRootLogin/d' /etc/ssh/sshd_config
  - echo "PermitRootLogin without-password" >> /etc/ssh/sshd_config
  - sed -i '/PubkeyAuthentication/d' /etc/ssh/sshd_config
  - echo "PubkeyAuthentication yes" >> /etc/ssh/sshd_config
  - sed -i '/PasswordAuthentication/d' /etc/ssh/sshd_config
  - echo "PasswordAuthentication no" >> /etc/ssh/sshd_config
  - systemctl restart sshd
  - echo "\$nrconf{kernelhints} = -1;" > /etc/needrestart/conf.d/99disable-prompt.conf
  - apt update
  - apt upgrade -y --allow-downgrades --allow-remove-essential --allow-change-held-packages
  - reboot

My solution is to edit line 22 in the clout-init.yml file to systemctl restart ssh || systemctl restart sshd in an attempt to target both SSH service names.

I also left out one small (huge) detail. On line 21 of cloud-init.yml, I also happened to have changed "PasswordAuthentication no" to "PasswordAuthentication yes".

Thus, conveniently disabling PasswordAuthentication, enabling access to the server (my mistake).

One could simply pipe echo "PasswordAuthentication no" >> /etc/ssh/sshd_config back into the session once connected, then wait for the system to reboot and then ssh back in. (unless you are plan adding a new server through Coolify I'd highly recommend doing that well after your new server is configured.)

I'm also testing @adrnd method to ssh into the session using ssh -o "IdentitiesOnly=yes" -i ~/.ssh/id_ed25519 root@serveripaddress, will follow up here.

The server kept asking me for my password. @adrnd's solution worked for me.

If I restart the server, I get root@[xxx.xxxx.xxx.xxx]: Permission denied (publickey).

Did you set the permissions right?

chmod -R 644 ~/.ssh/your_key.pub
chmod -R 600 ~/.ssh/authorized_keys

An alternative to @adrnd solution would be to create an ssh config entry like the following:

Host my_awesome_server
 HostName xxx.xxx.xxx.xxx
 User <YOUR_USER_NAME_SPECIFIED_IN_CLOUD_CONFIG>
 Port 22
 IdentityFile ~/.ssh/<PRIVATE_KEY_FILE>

And then run ssh my_awesome_server. This should enforce a user login on the given IP to use your public/private key for authentication. Make sure to also follow @swrrvr suggestion to add systemctl restart ssh || systemctl restart sshd to the cloud config. in line 22

Here's an updated version for ubuntu 24.04: https://gist.github.com/dziamid/0de2761e0ecc4b3e68e2461c60f82930

I am struggling with getting a new public key stored in known_hosts locally when trying to run ssh root@{ip-adress} rather than the public key I set in cloud.init script. Using @dziamid new file for Ubuntu 24.04, also added the systemctl restart ssh || systemctl restart sshd, does anyone know why this happens?