Command line. Packages. Mounts. File systems. Any standard anything. There's nothing unless you reinvent the wheel. Standardization and repeatability allow reuse of the work of many others. Unikernels throw 99.99% of it away.

Packages exist: https://repo.ops.city

Mounts also exist - in fact you can hotplug volumes on the fly on all the major clouds. People really like this cause they can do things like rotate ssl certs every few hours.

The file system exists - at the very least you need to load a program that sits on the filesystem but people are running webservers that write to temp files and load static assets and also databases.