Many older operating systems support only their one "native" file system, which does not bear any name apart from the name of the operating system itself.
https://en.wikipedia.org/wiki/List_of_file_systems
Pseudo- and virtual file systems
- devfs – Virtual file system in Unix-like operating systems for managing devices on-the-fly
- debugfs –Virtual file system in Linux for accessing and controlling kernel debugging.
- procfs – Pseudo-file system, used to access kernel information about processes
- tmpfs – in-memory temporary file system (on Linux platforms).
- specfs – Special File System for device files
- sysfs – Virtual file system in Unix-like operating systems holding information about buses, devices, firmware, filesystems, etc.
- wikifs – a server application for Plan 9's virtual, wiki, file system
- WinFS – Windows Future Storage, was planned as the successor to NTFS for Windows Vista.
https://en.wikipedia.org/wiki/List_of_file_systems
