DISKLABEL(5)              NetBSD File Formats Manual              DISKLABEL(5)

NAME
     disklabel -- disk pack label

SYNOPSIS
     #include <sys/disklabel.h>

DESCRIPTION
     Each disk or disk pack on a system may contain a disk label which pro-
     vides detailed information about the geometry of the disk and the parti-
     tions into which the disk is divided.  It should be initialized when the
     disk is formatted, and may be changed later with the disklabel(8) pro-
     gram.  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 file systems on the disk partitions.  Additional information is used
     by the file system in order to use the disk most efficiently and to
     locate important file system information.  The description of each parti-
     tion contains an identifier for the partition type (standard file system,
     swap area, etc.).  The file system updates the in-core copy of the label
     if it contains incomplete information about the file system.

     The label is located in the sector number returned by the
     getlabelsector(3) function, usually sector 0 where it may be found with-
     out any information about the disk geometry.  It is at an offset (speci-
     fied by the getlabeloffset(3) function) 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 overwrit-
     ten by pack-to-pack copies or swap operations; the DIOCWLABEL ioctl(2),
     which is done as needed by the disklabel(8) program.

     A copy of the in-core label for a disk can be obtained with the
     DIOCGDINFO ioctl(2); 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 DIOCSDINFO ioctl(2).  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 DIOCWDINFO ioctl(2) 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 disklabel(8).

     The format of the disk label, as specified in sys/disklabel.h, is

     /*
      * Disk description table, see disktab(5)
      */
     #define _PATH_DISKTAB   "/etc/disktab"

     /*
      * Each disk has a label which includes information about the hardware
      * disk geometry, file system partitions, and drive specific information.
      * The location of the label, as well as the number of partitions the
      * label can describe and the number of the "whole disk" (raw)
      * partition are machine dependent.
      */
     #include <machine/disklabel.h>

     /*
      * The absolute maximum number of disk partitions allowed.
      * This is the maximum value of MAXPARTITIONS for which 'struct disklabel'
      * is <= DEV_BSIZE bytes long.  If MAXPARTITIONS is greater than this, beware.
      */
     #define MAXMAXPARTITIONS        22
     #if MAXPARTITIONS > MAXMAXPARTITIONS
     #warning beware: MAXPARTITIONS bigger than MAXMAXPARTITIONS
     #endif


     #define DISKMAGIC       ((u_int32_t)0x82564557) /* The disk magic number */

     #ifndef _LOCORE
     struct disklabel {
             u_int32_t d_magic;              /* the magic number */
             u_int16_t d_type;               /* drive type */
             u_int16_t 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.
              */
             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

                             /* disk geometry: */
             u_int32_t d_secsize;            /* # of bytes per sector */
             u_int32_t d_nsectors;           /* # of data sectors per track */
             u_int32_t d_ntracks;            /* # of tracks per cylinder */
             u_int32_t d_ncylinders;         /* # of data cylinders per unit */
             u_int32_t d_secpercyl;          /* # of data sectors per cylinder */
             u_int32_t 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_int16_t d_sparespertrack;     /* # of spare sectors per track */
             u_int16_t d_sparespercyl;       /* # of spare sectors per cylinder */
             /*
              * Alternative cylinders include maintenance, replacement,
              * configuration description areas, etc.
              */
             u_int32_t 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_int16_t d_rpm;                /* rotational speed */
             u_int16_t d_interleave;         /* hardware sector interleave */
             u_int16_t d_trackskew;          /* sector 0 skew, per track */
             u_int16_t d_cylskew;            /* sector 0 skew, per cylinder */
             u_int32_t d_headswitch;         /* head switch time, usec */
             u_int32_t d_trkseek;            /* track-to-track seek, usec */
             u_int32_t d_flags;              /* generic flags */
     #define NDDATA 5
             u_int32_t d_drivedata[NDDATA];  /* drive-type specific information */
     #define NSPARE 5
             u_int32_t d_spare[NSPARE];      /* reserved for future use */
             u_int32_t d_magic2;             /* the magic number (again) */
             u_int16_t d_checksum;           /* xor of data incl. partitions */

                             /* file system and partition information: */
             u_int16_t d_npartitions;        /* number of partitions in following */
             u_int32_t d_bbsize;             /* size of boot area at sn0, bytes */
             u_int32_t d_sbsize;             /* max size of fs superblock, bytes */
             struct  partition {             /* the partition table */
                     u_int32_t p_size;       /* number of sectors in partition */
                     u_int32_t p_offset;     /* starting sector */
                     u_int32_t p_fsize;      /* file system basic fragment size */
                     u_int8_t p_fstype;      /* file system type, see below */
                     u_int8_t p_frag;        /* file system fragments per block */
                     union {
                             u_int16_t cpg;  /* UFS: FS cylinders per group */
                             u_int16_t sgs;  /* LFS: FS segment shift */
                     } __partition_u1;
     #define p_cpg   __partition_u1.cpg
     #define p_sgs   __partition_u1.sgs
             } d_partitions[MAXPARTITIONS];  /* actually may be more */
     };
     #else /* _LOCORE */
             /*
              * offsets for asm boot files.
              */
             .set    d_secsize,40
             .set    d_nsectors,44
             .set    d_ntracks,48
             .set    d_ncylinders,52
             .set    d_secpercyl,56
             .set    d_secperunit,60
             .set    d_end_,276              /* size of disk label */
     #endif /* _LOCORE */

     /* 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_HPIB      7       /* CS/80 on HP-IB */
     #define DTYPE_HPFL      8       /* HP Fiber-link */
     #define DTYPE_FLOPPY    10      /* floppy */
     #define DTYPE_CCD       11      /* concatenated disk device */
     #define DTYPE_VND       12      /* vnode pseudo-disk */
     #define DTYPE_ATAPI     13      /* ATAPI */
     #define DTYPE_RAID      14      /* RAIDframe */
     #define DTYPE_LD        15      /* logical disk */
     #define DTYPE_JFS2      16      /* IBM JFS2 */
     #define DTYPE_CGD       17      /* cryptographic pseudo-disk */
     #define DTYPE_VINUM     18      /* vinum volume obsolete */
     #define DTYPE_FLASH     19      /* flash memory device */

     #ifdef DKTYPENAMES
     static const char *const dktypenames[] = {
             "unknown",
             "SMD",
             "MSCP",
             "old DEC",
             "SCSI",
             "ESDI",
             "ST506",
             "HP-IB",
             "HP-FL",
             "type 9",
             "floppy",
             "ccd",
             "vnd",
             "ATAPI",
             "RAID",
             "ld",
             "jfs",
             "cgd",
             "obsolete vinum",
             "flash",
             NULL
     };
     #define DKMAXTYPES      (sizeof(dktypenames) / sizeof(dktypenames[0]) - 1)
     #endif

     /*
      * Filesystem type and version.
      * Used to interpret other file system-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 */
     #define FS_MSDOS        8       /* MSDOS file system */
     #define FS_BSDLFS       9       /* 4.4BSD log-structured file system */
     #define FS_OTHER        10      /* in use, but unknown/unsupported */
     #define FS_HPFS         11      /* OS/2 high-performance file system */
     #define FS_ISO9660      12      /* ISO 9660, normally CD-ROM */
     #define FS_BOOT         13      /* partition contains bootstrap */
     #define FS_ADOS         14      /* AmigaDOS fast file system */
     #define FS_HFS          15      /* Macintosh HFS */
     #define FS_FILECORE     16      /* Acorn Filecore Filing System */
     #define FS_EX2FS        17      /* Linux Extended 2 file system */
     #define FS_NTFS         18      /* Windows/NT file system */
     #define FS_RAID         19      /* RAIDframe component */
     #define FS_CCD          20      /* concatenated disk component */
     #define FS_JFS2         21      /* IBM JFS2 */
     #define FS_APPLEUFS     22      /* Apple UFS */
     #define FS_VINUM        23      /* Vinum */

     #ifdef  FSTYPENAMES
     static const char *const fstypenames[] = {
             "unused",
             "swap",
             "Version 6",
             "Version 7",
             "System V",
             "4.1BSD",
             "Eighth Edition",
             "4.2BSD",
             "MSDOS",
             "4.4LFS",
             "unknown",
             "HPFS",
             "ISO9660",
             "boot",
             "ADOS",
             "HFS",
             "FILECORE",
             "Linux Ext2",
             "NTFS",
             "RAID",
             "ccd",
             "jfs",
             "Apple UFS",
             "obsolete vinum",
             NULL
     };
     #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 */

     /*
      * Drive data for SCSI.
      */
     #define d_blind         d_drivedata[0]

     #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 are defined in sys/dkio.h.

     /*
      * 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 DIOCKLABEL      _IOW('d', 119, int) /* keep/drop label on close? */
     #define DIOCWLABEL      _IOW('d', 109, int) /* write en/disable label */

     #define DIOCSBAD        _IOW('d', 110, struct dkbad) /* set kernel dkbad */
     #define DIOCEJECT       _IOW('d', 112, int) /* eject removable disk */
     #define DIOCLOCK        _IOW('d', 113, int) /* lock/unlock pack */

             /* get default label, clear label */
     #define DIOCGDEFLABEL   _IOR('d', 114, struct disklabel)
     #define DIOCCLRLABEL    _IO('d', 115)

SEE ALSO
     disktab(5), disklabel(8), dkctl(8)

NetBSD 7.0                     February 24, 2006                    NetBSD 7.0

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©1996-2014 Modified for NetBSD by Kimmo Suominen