cloud-init
A tool that configures a fresh VM on first boot — setting hostname, users, SSH keys and packages automatically.
Cloud images for Ubuntu, Debian and others include cloud-init. In Proxmox you can attach a cloud-init drive to a template so new VMs come up pre-configured, making them reproducible and fast to deploy.
Related articles
Virtual Machine(VM)
A software-based computer that runs its own operating system on top of physical hardware via a hypervisor.
Hypervisor
Software that creates and manages virtual machines by allocating physical resources between them.
Headless
A server that runs without a monitor, keyboard or graphical desktop.