ServerPilot offers a light-weight control panel to manage your websites and apps on Ubuntu servers. When you connect a clean server to ServerPilot, they install a full PHP stack, with an SFTP user to manage your app files.
First, connect your server to ServerPilot with their tutorial here. When connecting the server to ServerPilot, you will be prompted to create a password for the SFTP user. When the server is installed completely, you can connect your server to Clustermin:
IP Address: your server IP address
Password: the password you created
Uncheck the box Create user, then click Connect.
Clustermin will generate a secure SSH key with a passphrase, and upload the public key onto your server. From then on, Clustermin connects and logs in to your server using SSH key only.
When the server is connected to Clustermin, click File Manager to manage your files on your server.
It's an online File Manager, and you can manage your files from anywhere with just a web browser.