'\"macro stdmacro
.if n .pH g4.fs_bfs @(#)fs_bfs	40.7 of 1/17/90
.\" Copyright 1989 AT&T
'\"!tbl | mmdoc
.nr X
.if \nX=0 .ds x} fs 4 "bfs" "\&"
.if \nX=1 .ds x} fs 4 "bfs"
.if \nX=2 .ds x} fs 4 "" "\&"
.if \nX=3 .ds x} fs "" "" "\&"
.TH \*(x}
.SH NAME
fs (bfs) \- format of the bfs file system volume
.SH SYNOPSIS
\f4#include <sys/types.h>
.br
#include <sys/fs/bfs.h>\fP
.SH DESCRIPTION
The bfs superblock is stored on sector 0. Its format is:
.PP
.ps -1
.vs -1
.nf
.ft 4
.ta .35i .7i 2.25i
	struct bdsuper
	{
		long bdsup_bfsmagic;	/* Magic number */
		off_t bdsup_start;	/* Filesystem data start offset */
		off_t bdsup_end;	/* Filesystem data end offset */

		/*
		 * Sanity words
		 */
		daddr_t bdcp_fromblock;	/* "From" block of current transfer */
		daddr_t bdcp_toblock;	/* "To" block of current transfer */
		daddr_t bdcpb_fromblock;	/* Backup of "from" block */
		daddr_t bdcpb_toblock;	/* Backup of "to" block */
	};

	#define BFS_MAGIC   0xBADFACE	/* bfs magic number */
.ft 1
.ps +1
.vs +1
.fi
.PP
The sanity words are  used to promote sanity during compaction.
They are used by \f4fsck\fP(1M) to recover from a system
crash at any point during compaction.
See "Storage Blocks under \f4bfs\fP" in the "The \f4bfs\fP File System" section
of chapter 5 in the \f2System Administratror's Guide\fP
for a description
of compaction.
.SH SEE ALSO
\f4bfs\fP-specific \f4inode\fP(4)
