Subject: Re: Off topic (where are the superblocks?)
To: None <current-users@NetBSD.ORG>
From: Hiroyuki Ito <>
List: current-users
Date: 06/02/1996 09:48:17
Andrew Wheadon <> wrote:
> 	I just need a quick info, where are the first superblocks
> (when the one at 32 has gone too.) ?

% uname -srm
NetBSD 1.1B i386
% sed -n 38,67p /usr/include/ufs/ffs/fs.h
 * Each disk drive contains some number of file systems.
 * A file system consists of a number of cylinder groups.
 * Each cylinder group has inodes and data.
 * A file system is described by its super-block, which in turn
 * describes the cylinder groups.  The super-block is critical
 * data and is replicated in each cylinder group to protect against
 * catastrophic loss.  This is done at `newfs' time and the critical
 * super-block data does not change, so the copies need not be
 * referenced further unless disaster strikes.
 * For file system fs, the offsets of the various blocks of interest
 * are given in the super block as:
 *	[fs->fs_sblkno]		Super-block
 *	[fs->fs_cblkno]		Cylinder group block
 *	[fs->fs_iblkno]		Inode blocks
 *	[fs->fs_dblkno]		Data blocks
 * The beginning of cylinder group cg in fs, is given by
 * the ``cgbase(fs, cg)'' macro.
 * The first boot and super blocks are given in absolute disk addresses.
 * The byte-offset forms are preferred, as they don't imply a sector size.
#define BBSIZE		8192
#define SBSIZE		8192
#define	BBOFF		((off_t)(0))
#define	SBOFF		((off_t)(BBOFF + BBSIZE))
#define	BBLOCK		((daddr_t)(0))
#define	SBLOCK		((daddr_t)(BBLOCK + BBSIZE / DEV_BSIZE))

Hiroyuki Ito