+.\" Copyright (c) 1987, 1991 Regents of the University of California.
+.\" All rights reserved.
+.\"
+.\" This code is derived from software contributed to Berkeley by
+.\" Symmetric Computer Systems.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\" must display the following acknowledgement:
+.\" This product includes software developed by the University of
+.\" California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\" may be used to endorse or promote products derived from this software
+.\" without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" @(#)disklabel.5.5 6.6 (Berkeley) 5/10/91
+.\"
+.Dd May 10, 1991
+.Dt DISKLABEL 5
+.Os
+.Sh NAME
+.Nm disklabel
+.Nd disk pack label
+.Sh SYNOPSIS
+.Fd #include <sys/disklabel.h>
+.Sh DESCRIPTION
+Each disk or disk pack on a system may contain a disk label
+which provides detailed information
+about the geometry of the disk and the partitions into which the disk
+is divided.
+It should be initialized when the disk is formatted,
+and may be changed later with the
+.Xr disklabel 8
+program.
+This information is used by the system disk driver and by the bootstrap
+program to determine how to program the drive
+and where to find the filesystems on the disk partitions.
+Additional information is used by the filesystem in order
+to use the disk most efficiently and to locate important filesystem information.
+The description of each partition contains an identifier for the partition
+type (standard filesystem, swap area, etc.).
+The filesystem updates the in-core copy of the label if it contains
+incomplete information about the filesystem.
+.Pp
+The label is located in sector number
+.Dv LABELSECTOR
+of the drive, usually sector 0 where it may be found
+without any information about the disk geometry.
+It is at an offset
+.Dv LABELOFFSET
+from the beginning of the sector, to allow room for the initial bootstrap.
+The disk sector containing the label is normally made read-only
+so that it is not accidentally overwritten by pack-to-pack copies
+or swap operations;
+the
+.Dv DIOCWLABEL
+.Xr ioctl 2 ,
+which is done as needed by the
+.Xr disklabel
+program.
+.Pp
+A copy of the in-core label for a disk can be obtained with the
+.Dv DIOCGDINFO
+.Xr ioctl ;
+this works with a file descriptor for a block or character (``raw'') device
+for any partition of the disk.
+The in-core copy of the label is set by the
+.Dv DIOCSDINFO
+.Xr ioctl .
+The offset of a partition cannot generally be changed while it is open,
+nor can it be made smaller while it is open.
+One exception is that any change is allowed if no label was found
+on the disk, and the driver was able to construct only a skeletal label
+without partition information.
+Finally, the
+.Dv DIOCWDINFO
+.Xr ioctl
+operation sets the in-core label and then updates the on-disk label;
+there must be an existing label on the disk for this operation to succeed.
+Thus, the initial label for a disk or disk pack must be installed
+by writing to the raw disk.
+All of these operations are normally done using
+.Xr disklabel .
+.Pp
+The format of the disk label, as specified in
+.Aw Pa sys/disklabel.h ,
+is
+.Bd -literal
+/*
+* Disk description table, see disktab(5)
+*/
+#define DISKTAB "/etc/disktab"
+
+/*
+* Each disk has a label which includes information about the hardware
+* disk geometry, filesystem partitions, and drive specific information.
+* The label is in block 0 or 1, possibly offset from the beginning
+* to leave room for a bootstrap, etc.
+*/
+
+#define LABELSECTOR 0 /* sector containing label */
+#define LABELOFFSET 64 /* offset of label in sector */
+#define DISKMAGIC ((u_long) 0x82564557) /* The disk magic number */
+#ifndef MAXPARTITIONS
+#define MAXPARTITIONS 8
+#endif
+
+#ifndef LOCORE
+struct disklabel {
+ u_long d_magic; /* the magic number */
+ short d_type; /* drive type */
+ short d_subtype; /* controller/d_type specific */
+ char d_typename[16]; /* type name, e.g. "eagle" */
+ /*
+ * d_packname contains the pack identifier and is returned when
+ * the disklabel is read off the disk or in-core copy.
+ * d_boot0 and d_boot1 are the (optional) names of the
+ * primary (block 0) and secondary (block 1-15) bootstraps
+ * as found in /usr/mdec. These are returned when using
+ * getdiskbyname(3)
+ to retrieve the values from /etc/disktab.
+ */
+#if defined(KERNEL) || defined(STANDALONE)
+ char d_packname[16]; /* pack identifier */
+#else
+ union {
+ char un_d_packname[16]; /* pack identifier */
+ struct {
+ char *un_d_boot0; /* primary bootstrap name */
+ char *un_d_boot1; /* secondary bootstrap name */
+ } un_b;
+ } d_un;
+
+#define d_packname d_un.un_d_packname
+#define d_boot0 d_un.un_b.un_d_boot0
+#define d_boot1 d_un.un_b.un_d_boot1
+#endif /* ! KERNEL or STANDALONE */
+
+ /* disk geometry: */
+ u_long d_secsize; /* # of bytes per sector */
+ u_long d_nsectors; /* # of data sectors per track */
+ u_long d_ntracks; /* # of tracks per cylinder */
+ u_long d_ncylinders; /* # of data cylinders per unit */
+ u_long d_secpercyl; /* # of data sectors per cylinder */
+ u_long d_secperunit; /* # of data sectors per unit */
+ /*
+ * Spares (bad sector replacements) below
+ * are not counted in d_nsectors or d_secpercyl.
+ * Spare sectors are assumed to be physical sectors
+ * which occupy space at the end of each track and/or cylinder.
+ */
+ u_short d_sparespertrack; /* # of spare sectors per track */
+ u_short d_sparespercyl; /* # of spare sectors per cylinder */
+ /*
+ * Alternate cylinders include maintenance, replacement,
+ * configuration description areas, etc.
+ */
+ u_long d_acylinders; /* # of alt. cylinders per unit */
+
+ /* hardware characteristics: */
+ /*
+ * d_interleave, d_trackskew and d_cylskew describe perturbations
+ * in the media format used to compensate for a slow controller.
+ * Interleave is physical sector interleave, set up by the formatter
+ * or controller when formatting. When interleaving is in use,
+ * logically adjacent sectors are not physically contiguous,
+ * but instead are separated by some number of sectors.
+ * It is specified as the ratio of physical sectors traversed
+ * per logical sector. Thus an interleave of 1:1 implies contiguous
+ * layout, while 2:1 implies that logical sector 0 is separated
+ * by one sector from logical sector 1.
+ * d_trackskew is the offset of sector 0 on track N
+ * relative to sector 0 on track N-1 on the same cylinder.
+ * Finally, d_cylskew is the offset of sector 0 on cylinder N
+ * relative to sector 0 on cylinder N-1.
+ */
+ u_short d_rpm; /* rotational speed */
+ u_short d_interleave; /* hardware sector interleave */
+ u_short d_trackskew; /* sector 0 skew, per track */
+ u_short d_cylskew; /* sector 0 skew, per cylinder */
+ u_long d_headswitch; /* head switch time, usec */
+ u_long d_trkseek; /* track-to-track seek, usec */
+ u_long d_flags; /* generic flags */
+#define NDDATA 5
+ u_long d_drivedata[NDDATA]; /* drive-type specific information */
+#define NSPARE 5
+ u_long d_spare[NSPARE]; /* reserved for future use */
+ u_long d_magic2; /* the magic number (again) */
+ u_short d_checksum; /* xor of data incl. partitions */
+
+ /* filesystem and partition information: */
+ u_short d_npartitions; /* number of partitions in following */
+ u_long d_bbsize; /* size of boot area at sn0, bytes */
+ u_long d_sbsize; /* max size of fs superblock, bytes */
+ struct partition { /* the partition table */
+ u_long p_size; /* number of sectors in partition */
+ u_long p_offset; /* starting sector */
+ u_long p_fsize; /* filesystem basic fragment size */
+ u_char p_fstype; /* filesystem type, see below */
+ u_char p_frag; /* filesystem fragments per block */
+ u_short p_cpg; /* filesystem cylinders per group */
+ } d_partitions[MAXPARTITIONS]; /* actually may be more */
+};
+
+/* d_type values: */
+#define DTYPE_SMD 1 /* SMD, XSMD; VAX hp/up */
+#define DTYPE_MSCP 2 /* MSCP */
+#define DTYPE_DEC 3 /* other DEC (rk, rl) */
+#define DTYPE_SCSI 4 /* SCSI */
+#define DTYPE_ESDI 5 /* ESDI interface */
+#define DTYPE_ST506 6 /* ST506 etc. */
+#define DTYPE_FLOPPY 10 /* floppy */
+
+#ifdef DKTYPENAMES
+static char *dktypenames[] = {
+ "unknown",
+ "SMD",
+ "MSCP",
+ "old DEC",
+ "SCSI",
+ "ESDI",
+ "type 6",
+ "type 7",
+ "type 8",
+ "type 9",
+ "floppy",
+ 0
+};
+#define DKMAXTYPES (sizeof(dktypenames) / sizeof(dktypenames[0]) - 1)
+#endif
+
+/*
+* Filesystem type and version.
+* Used to interpret other filesystem-specific
+* per-partition information.
+*/
+#define FS_UNUSED 0 /* unused */
+#define FS_SWAP 1 /* swap */
+#define FS_V6 2 /* Sixth Edition */
+#define FS_V7 3 /* Seventh Edition */
+#define FS_SYSV 4 /* System V */
+#define FS_V71K 5 /* V7 with 1K blocks (4.1, 2.9) */
+#define FS_V8 6 /* Eighth Edition, 4K blocks */
+#define FS_BSDFFS 7 /* 4.2BSD fast file system */
+
+#ifdef DKTYPENAMES
+static char *fstypenames[] = {
+ "unused",
+ "swap",
+ "Version 6",
+ "Version 7",
+ "System V",
+ "4.1BSD",
+ "Eighth Edition",
+ "4.2BSD",
+ 0
+};
+#define FSMAXTYPES (sizeof(fstypenames) / sizeof(fstypenames[0]) - 1)
+#endif
+
+/*
+* flags shared by various drives:
+*/
+#define D_REMOVABLE 0x01 /* removable media */
+#define D_ECC 0x02 /* supports ECC */
+#define D_BADSECT 0x04 /* supports bad sector forw. */
+#define D_RAMDISK 0x08 /* disk emulator */
+#define D_CHAIN 0x10 /* can do back-back transfers */
+
+/*
+* Drive data for SMD.
+*/
+
+#define d_smdflags d_drivedata[0]
+#define D_SSE 0x1 /* supports skip sectoring */
+#define d_mindist d_drivedata[1]
+#define d_maxdist d_drivedata[2]
+#define d_sdist d_drivedata[3]
+
+/*
+* Drive data for ST506.
+*/
+#define d_precompcyl d_drivedata[0]
+#define d_gap3 d_drivedata[1] /* used only when formatting */
+
+#ifndef LOCORE
+/*
+* Structure used to perform a format
+* or other raw operation, returning data
+* and/or register values.
+* Register identification and format
+* are device- and driver-dependent.
+*/
+struct format_op {
+ char *df_buf;
+ int df_count; /* value-result */
+ daddr_t df_startblk;
+ int df_reg[8]; /* result */
+};
+
+/*
+* Structure used internally to retrieve
+* information about a partition on a disk.
+*/
+struct partinfo {
+ struct disklabel *disklab;
+ struct partition *part;
+};
+
+/*
+* Disk-specific ioctls.
+*/
+ /* get and set disklabel; DIOCGPART used internally */
+#define DIOCGDINFO _IOR('d', 101, struct disklabel) /* get */
+#define DIOCSDINFO _IOW('d', 102, struct disklabel) /* set */
+#define DIOCWDINFO _IOW('d', 103, struct disklabel) /* set, update disk */
+#define DIOCGPART _IOW('d', 104, struct partinfo) /* get partition */
+
+/* do format operation, read or write */
+#define DIOCRFORMAT _IOWR('d', 105, struct format_op)
+#define DIOCWFORMAT _IOWR('d', 106, struct format_op)
+
+#define DIOCSSTEP _IOW('d', 107, int) /* set step rate */
+#define DIOCSRETRIES _IOW('d', 108, int) /* set # of retries */
+#define DIOCWLABEL _IOW('d', 109, int) /* write en/disable label */
+
+#define DIOCSBAD _IOW('d', 110, struct dkbad) /* set kernel dkbad */
+
+#endif LOCORE
+.Ed
+.Sh SEE ALSO
+.Xr disktab 5 ,
+.Xr disklabel 8
+.Sh HISTORY
+The
+.Nm
+file format is
+.Ud .
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