SSH keys¶

Mnemosynce uses SSH keys for two distinct purposes. Understanding which key does what will save you time when setting things up.

Two key roles¶

Source keys — managed in the web UI¶

Go to Settings → SSH Keys (or the SSH Keys step of the setup wizard).

Generating a key¶

1. Enter a name — letters, numbers, hyphens, and underscores only (e.g. desktop_mark).
2. Optionally add a comment (e.g. backup-server/desktop_mark).
3. Click Generate.

The private key is saved to /data/ssh/<name> with mode 600. The public key is shown immediately.

Copying the public key to a remote host¶

After generating, copy the public key string displayed on screen and paste it into ~/.ssh/authorized_keys on the remote machine:

# On the remote machine (e.g. your desktop)
echo "ssh-ed25519 AAAA...rest-of-key..." >> ~/.ssh/authorized_keys

Or use ssh-copy-id from the backup server if you still have password access:

ssh-copy-id -i /data/ssh/desktop_mark.pub user@desktop

Testing the key¶

After copying the public key, go to Settings → Connections and run an SSH test with the same user@host pair. A successful test confirms the key is trusted.

Remote sync key — manual setup¶

The sync_backup_to_remote.sh script always uses the key at /root/.ssh/id_ed25519_backup. Generate it once on the backup server:

ssh-keygen -t ed25519 -f /root/.ssh/id_ed25519_backup -N ""
ssh-copy-id -i /root/.ssh/id_ed25519_backup.pub user@backup-host

This key is not managed by the web UI and is not stored in /data/ssh/. However, the application detects it automatically at startup and includes it in the generated /data/ssh/ssh_config, so the sync script honours it alongside any UI-managed keys.

Trusting remote host keys¶

Before an SSH connection can succeed non-interactively (during a backup run or a connection test), the remote host's public key must be present in known_hosts. Use the Trust host key panel on Settings → Connections:

1. Enter the hostname (e.g. pibackup or desktop-ubuntu).
2. Click Trust host key.

The application runs ssh-keyscan against that host and appends the result to /data/ssh/known_hosts. This file is inside the persistent data volume so it survives container restarts.

Deleting a key¶

On the SSH Keys page, click Delete next to any key. Both the private and public key files are removed. If a backup task references that key's host, the backup step will fail until a new key is generated and installed.