System Administration Guide: Devices and File Systems

UFS File System Features

UFS is the default disk-based file system in Oracle Solaris OS. Most often, when you administer a disk-based file system, you are administering UFS file systems. UFS provides the following features.

UFS Feature 


Extended fundamental types (EFT) 

Provides 32-bit user ID (UID), group ID (GID), and device numbers.

Large file systems 

Allows files of about 1 terabyte in size in a file system that can be up to 16 terabytes in size. You can create a multiterabyte UFS file system on a disk with an EFI disk label.


UFS logging bundles the multiple metadata changes that comprise a complete UFS operation into a transaction. Sets of transactions are recorded in an on-disk log and are applied to the actual UFS file system's metadata. 

Multiterabyte file systems 

A multiterabyte file system enables creation of a UFS file system up to approximately 16 terabytes of usable space, minus approximately one percent overhead.

State flags 

Shows the state of the file system: clean, stable, active, logging, or unknown. These flags eliminate unnecessary file system checks. If the file system is “clean,” “stable,” or “logging,” file system checks are not run.

For detailed information about the UFS file system structure, see Chapter 22, UFS File System (Reference).