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DISKLABEL(5)              FreeBSD 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 sector number LABELSECTOR of the drive, usually
     sector 0 where it may be found without any information about the disk
     geometry.  It is at an offset LABELOFFSET from the beginning of the sec-
     tor, to allow room for the initial bootstrap.  The disk sector containing
     the label is normally made read-only so that it is not accidentally over-
     written 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

     #ifndef _SYS_DISKLABEL_H_
     #define _SYS_DISKLABEL_H_

     #ifndef _KERNEL
     #include <sys/types.h>
     #endif
     #include <sys/ioccom.h>

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

     /*
      * 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.
      */

     /* XXX these should be defined per controller (or drive) elsewhere, not here! */
     #ifdef __i386__
     #define LABELSECTOR     1                       /* sector containing label */
     #define LABELOFFSET     0                       /* offset of label in sector */
     #endif

     #ifdef __alpha__
     #define LABELSECTOR     0
     #define LABELOFFSET     64
     #endif

     #ifndef LABELSECTOR
     #define LABELSECTOR     0                       /* sector containing label */
     #endif

     #ifndef LABELOFFSET
     #define LABELOFFSET     64                      /* offset of label in sector */
     #endif

     #define DISKMAGIC       ((u_int32_t)0x82564557) /* The disk magic number */
     #ifndef MAXPARTITIONS
     #define MAXPARTITIONS   8
     #endif

     #define LABEL_PART      2               /* partition containing label */
     #define RAW_PART        2               /* partition containing whole disk */
     #define SWAP_PART       1               /* partition normally containing swap */

     #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 /boot.  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 */
             /*
              * Alternate 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 */

                             /* filesystem 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;      /* filesystem basic fragment size */
                     u_int8_t p_fstype;      /* filesystem type, see below */
                     u_int8_t p_frag;        /* filesystem 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 */
     #define DTYPE_VINUM             12              /* vinum volume */
     #define DTYPE_DOC2K             13              /* Msys DiskOnChip */

     #if defined(PC98) && !defined(PC98_ATCOMPAT)
     #define DSTYPE_SEC256           0x80            /* physical sector size=256 */
     #endif

     #ifdef DKTYPENAMES
     static char *dktypenames[] = {
             "unknown",
             "SMD",
             "MSCP",
             "old DEC",
             "SCSI",
             "ESDI",
             "ST506",
             "HP-IB",
             "HP-FL",
             "type 9",
             "floppy",
             "CCD",
             "Vinum",
             "DOC2K",
             NULL
     };
     #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 */
     #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_VINUM        14              /* Vinum drive */

     #ifdef  DKTYPENAMES
     static char *fstypenames[] = {
             "unused",
             "swap",
             "Version 6",
             "Version 7",
             "System V",
             "4.1BSD",
             "Eighth Edition",
             "4.2BSD",
             "MSDOS",
             "4.4LFS",
             "unknown",
             "HPFS",
             "ISO9660",
             "boot",
             "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;
     };

     /* DOS partition table -- located in boot block */

     #if defined(PC98) && !defined(PC98_ATCOMPAT)
     #define DOSBBSECTOR     0       /* DOS boot block relative sector number */
     #define DOSLABELSECTOR  1       /* 0: 256b/s, 1: 512b/s */
     #define DOSPARTOFF      0
     #define NDOSPART        16
     #define DOSPTYP_386BSD  0x94    /* 386BSD partition type */
     #define MBR_PTYPE_FreeBSD 0x94  /* FreeBSD partition type */

     struct dos_partition {
             unsigned char   dp_mid;
     #define DOSMID_386BSD           (0x14|0x80) /* 386bsd|bootable */
             unsigned char   dp_sid;
     #define DOSSID_386BSD           (0x44|0x80) /* 386bsd|active */
             unsigned char   dp_dum1;
             unsigned char   dp_dum2;
             unsigned char   dp_ipl_sct;
             unsigned char   dp_ipl_head;
             unsigned short  dp_ipl_cyl;
             unsigned char   dp_ssect;       /* starting sector */
             unsigned char   dp_shd;         /* starting head */
             unsigned short  dp_scyl;        /* starting cylinder */
             unsigned char   dp_esect;       /* end sector */
             unsigned char   dp_ehd;         /* end head */
             unsigned short  dp_ecyl;        /* end cylinder */
             unsigned char   dp_name[16];
     };

     #else /* IBMPC */
     #define DOSBBSECTOR     0       /* DOS boot block relative sector number */
     #define DOSPARTOFF      446
     #define NDOSPART        4
     #define DOSPTYP_386BSD  0xa5    /* 386BSD partition type */

     struct dos_partition {
             unsigned char   dp_flag;        /* bootstrap flags */
             unsigned char   dp_shd;         /* starting head */
             unsigned char   dp_ssect;       /* starting sector */
             unsigned char   dp_scyl;        /* starting cylinder */
             unsigned char   dp_typ;         /* partition type */
             unsigned char   dp_ehd;         /* end head */
             unsigned char   dp_esect;       /* end sector */
             unsigned char   dp_ecyl;        /* end cylinder */
             u_int32_t       dp_start;       /* absolute starting sector number */
             u_int32_t       dp_size;        /* partition size in sectors */
     };
     #endif

     #define DPSECT(s) ((s) & 0x3f)          /* isolate relevant bits of sector */
     #define DPCYL(c, s) ((c) + (((s) & 0xc0)<<2)) /* and those that are cylinder */

     /*
      * 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 */

     #define DIOCWLABEL      _IOW('d', 109, int)     /* write en/disable label */

     #ifdef _KERNEL

     /*
      * XXX encoding of disk minor numbers, should be elsewhere.
      *
      * See <sys/reboot.h> for a possibly better encoding.
      *
      * "cpio -H newc" can be used to back up device files with large minor
      * numbers (but not ones >= 2^31).  Old cpio formats and all tar formats
      * don't have enough bits, and cpio and tar don't notice the lossage.
      * There are also some sign extension bugs.
      */

     /*
            3                   2                   1                   0
          1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
         _________________________________________________________________
         | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
         -----------------------------------------------------------------
         |    TYPE     |UNIT_2 | SLICE   |  MAJOR?       |  UNIT   |PART |
         -----------------------------------------------------------------
     */
     #define dkmakeminor(unit, slice, part) \
             (((slice) << 16) | (((unit) & 0x1e0) << 16) | \
             (((unit) & 0x1f) << 3) | (part))
     static __inline dev_t
     dkmodpart(dev_t dev, int part)
     {
             return (makedev(major(dev), (minor(dev) & ~7) | part));
     }

     static __inline dev_t
     dkmodslice(dev_t dev, int slice)
     {
             return (makedev(major(dev), (minor(dev) & ~0x1f0000) | (slice << 16)));
     }

     #define dkpart(dev)             (minor(dev) & 7)
     #define dkslice(dev)            ((minor(dev) >> 16) & 0x1f)
     #define dktype(dev)             ((minor(dev) >> 25) & 0x7f)

     static __inline u_int
     dkunit(dev_t dev)
     {
             return (((minor(dev) >> 16) & 0x1e0) | ((minor(dev) >> 3) & 0x1f));
     }

     struct  buf;
     struct  buf_queue_head;

     int     bounds_check_with_label __P((struct buf *bp, struct disklabel *lp,
                                          int wlabel));
     void    diskerr __P((struct buf *bp, char *what, int pri, int blkdone,
                          struct disklabel *lp));
     void    disksort __P((struct buf *ap, struct buf *bp));
     u_int   dkcksum __P((struct disklabel *lp));
     char    *readdisklabel __P((dev_t dev, struct disklabel *lp));
     void    bufqdisksort __P((struct buf_queue_head *ap, struct buf *bp));
     int     setdisklabel __P((struct disklabel *olp, struct disklabel *nlp,
                               u_long openmask));
     int     writedisklabel __P((dev_t dev, struct disklabel *lp));
     #ifdef __alpha__
     void    alpha_fix_srm_checksum __P((struct buf *bp));
     #endif

     #endif /* _KERNEL */

     #endif /* LOCORE */

     #ifndef _KERNEL
     __BEGIN_DECLS
     struct disklabel *getdiskbyname __P((const char *));
     __END_DECLS
     #endif

     #endif /* !_SYS_DISKLABEL_H_ */

SEE ALSO
     disktab(5), disklabel(8)

FreeBSD 4.10                     June 5, 1993                     FreeBSD 4.10

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO

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