136 lines
4.7 KiB
Groff
136 lines
4.7 KiB
Groff
.\" $NetBSD: ahdi.4,v 1.1 2000/02/05 20:40:36 jdc Exp $
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.\"
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.\" Copyright (c) 1998 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Julian Coleman.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd January 5, 2000
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.Dt ahdi 4
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.Sh NAME
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.Nm ahdi
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.Nd format of AHDI partitioned disk
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.Sh DESCRIPTION
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The AHDI disk format consists of a root sector (sector 0) containing:
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.Bl -column "Offset" "Contents" -offset indent
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.It Em Offset Ta Em Contents
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.It Li 0x000 Ta
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Boot code (can be empty)
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.It Li 0x1c2 Ta
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Size of hard disk in sectors
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.It Li 0x1c6 Ta
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First partition information
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.It Li 0x1d2 Ta
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Second partition information
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.It Li 0x1de Ta
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Third partition information
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.It Li 0x1ea Ta
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Fourth partition information
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.It Li 0x1f6 Ta
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Sector containing start of bad sector list (usually 1)
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.It Li 0x1fa Ta
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Length of bad sector list, in sectors (usually 1)
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.It Li 0x1fe Ta
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Root sector checksum
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.El
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.Pp
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The format of the partition information is:
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.Bl -column "Offset" "Contents" -offset indent
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.It Li Em Offset Ta Em Contents
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.It Li 0x00 Ta
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Partition flag (0x1 if partition is valid, 0x0 otherwise)
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.It Li 0x01 Ta
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Partition ID (e.g. NBD, GEM)
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.It Li 0x04 Ta
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Partition start sector
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.It Li 0x08 Ta
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Partition size in sectors
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.El
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.Pp
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The offsets are in bytes from the start of the sector.
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.Pp
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If the partition ID is
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.Em XGM ,
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the partition is a pointer to an extended partition, where the start
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sector is the sector containing the auxiliary root and the size is the
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size of the auxiliary root and any partitions it references.
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.Pp
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The format of the auxiliary root sector is the same as that of the root
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sector. However, the only valid fields are at most two of the partition
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structures. Only one of these can reference to a non-XGM partition. The
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start sector in the partition structure contains the offset of the partition
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from the start of the
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.Em first
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auxiliary partition.
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.Pp
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Partitions referenced from the root sector (sector 0) are known as
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.Em primary partitions ,
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while those referenced from auxiliary root sectors are known as
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.Em extended partitions .
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.Pp
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The bad sector list consists of 3-byte entries. The first entry contains
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the number of vendor bad sectors recorded. The first byte of the second
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entry contains a checksum byte which causes the bytewise sum of the whole
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bad sector list to be 0xa5. The remaining entries are vendor bad sectors
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followed by user bad sectors.
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.Pp
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The
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.Nx
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disklabel is written in the first partition with ID
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.Em NBD
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or
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.Em RAW .
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If neither of these partition ID's is present on the disk, no
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.Nx
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disklabel will exist on the disk. In this case, an in-core disklabel is
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automatically generated by the
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.Nx
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kernel.
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.Sh NOTES
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The AHDI disk format only supports media with a 512 byte sector size.
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.Pp
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It is only possible to boot from a
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.Em primary partition .
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.Sh SEE ALSO
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.Xr ahdi_buildlabel 3 ,
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.Xr ahdi_checklabel 3 ,
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.Xr ahdi_readlabel 3 ,
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.Xr ahdi_writedisktab 3 ,
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.Xr ahdi_writelabel 3
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.Sh HISTORY
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The
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.Nm libahdi
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package appeared in
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.Nx 1.5 .
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.Sh AUTHORS
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.An Julian Coleman, Waldi Ravens, Leo Weppelman
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