Boot File System

The Boot File System (named BFS on Linux, but BFS also refers to the Be File System) was used on UnixWare to store files necessary to its boot process.[1]

Developer(s)Bell Labs
Full nameBoot File System
Introducedwith UNIX System V
Partition identifier0x63 (MBR)
Directory contentssingle inode table
File allocation16-bit inodes
Max. filename length14 characters
Supported operating systemsUnixWare

It does not support directories, and only allows contiguous allocation for files, to make it simpler to be used by the boot loader.


Besides the UnixWare support, Martin Hinner wrote a bfs kernel module for Linux that supports it.[2]

He documented the file system layout as part of the process.[3]

The Linux kernel implementation of BFS was written by Tigran Aivazian and it became part of the standard kernel sources on 28 October 1999 (Linux version 2.3.25).[4]

The original BFS was written at AT&T Bell Laboratories for the UNIX System V, Version 4.0 porting base in 1986. It was written by Ron Schnell, who is also the author of Dunnet (game).

BFS was the first non-S5 (System V) Filesystem written using VFS (Virtual Filesystem) for AT&T UNIX.


  1. "UnixWare architecture supports multiplatform interoperability". InfoWorld: 66. 28 June 1993.
  2. Martin Hinner (1999). "UnixWare boot filesystem for Linux". Martin Hinner. Retrieved 2008-12-21.
  3. Martin Hinner (1999). "The BFS filesystem structure". Martin Hinner. Retrieved 2008-12-21.
  4. Tigran Aivazian (1999). "Linux Implementation of SCO UnixWare BFS". Tigran Aivazian. Retrieved 2018-06-14.
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