SSH setup — Moodle migration VPS

Wednesday, October 29, 2025

Context Fresh OVH VPS (Ubuntu 25.04) for the Moodle migration. key-based SSH with simple commands to remember.

Goal Connect as ubuntu via SSH keys (no passwords long-term), with a per-host key + alias.

What I did

ssh-keygen -t ed25519 -C "taksumaq@ubuntu ovh-newroad-moodle"
# saved as: ~/.ssh/id_ed25519_ovh-newroad-moodle  (and .pub)

OVH docs suggested setting -a 256 (KDF rounds). I decided not to and use defaults.

Created ~/.ssh/config:

Host ovh-newroad
  HostName 158.69.206.122
  User ubuntu
  IdentityFile ~/.ssh/id_ed25519_ovh-newroad-moodle
  IdentitiesOnly yes

Permissions:

chmod 700 ~/.ssh
chmod 600 ~/.ssh/config

First contact shows the host-key prompt — typed yes. OVH enforces a password change on first login, so I forced a TTY:

ssh -tt ovh-newroad
# changed the initial password when prompted

ssh-copy-id -i ~/.ssh/id_ed25519_ovh-newroad-moodle.pub ovh-newroad

Then tested key login (was asked to provide my key passphrase on a popup prompt):

ssh ovh-newroad

The authorization prompt on first login needed the passphrase created when generating the ssh key.
File perms matter: ~/.ssh 700, ~/.ssh/config 600, server-side ~/.ssh/authorized_keys 600.
When reinstalling the system the host’s key change and hence the key entries for that host need to be remove. We do so by running ssh-keygen -R <hostname>. Otherwise it won’t let you connect.