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Annotation of src/sbin/fdisk/fdisk.8, Revision 1.5

1.5     ! jtc         1: .\"    $Id: fdisk.8,v 1.4 1994/01/14 02:05:47 jtc Exp $        -*- nroff -*-
1.1       cgd         2: .Dd April 4, 1993
                      3: .Dt FDISK 8
                      4: .\".Os BSD 4
                      5: .Sh NAME
                      6: .Nm fdisk
1.5     ! jtc         7: .Nd DOS partition maintenance program
1.1       cgd         8: .Sh SYNOPSIS
                      9: .Nm
                     10: .Op Fl i
                     11: .Op Fl u
                     12: .Bl -tag -width time
                     13: .It Fl i
                     14: Initializes sector 0 of the disk.
                     15: .It Fl u
                     16: Is used for updating (editing) sector 0 of the disk.
                     17: .El
                     18: .Sh PROLOGUE
                     19: In order for the BIOS to boot the kernel,
                     20: certain conventions must be adhered to.
                     21: Sector 0 of the disk must contain boot code,
                     22: a partition table,
                     23: and a magic number.
                     24: BIOS partitions can be used to break the disk up into several pieces.
                     25: The BIOS brings in sector 0
                     26: (does it really use the code?)
                     27: and verifies the magic number.
                     28: It then searches the 4 BIOS partitions described by sector 0
                     29: to determine which of them is
                     30: .Em active.
                     31: This boot then brings in the secondary boot block from the
                     32: .Em active
                     33: partition and runs it.
                     34: Under DOS,
                     35: you could have one or more partitions with one
                     36: .Em active.
                     37: The DOS
                     38: .Nm
                     39: program can be used to divide space on the disk into partitions and set one
                     40: .Em active.
                     41: .Sh DESCRIPTION
1.3       cgd        42: The NetBSD program
1.1       cgd        43: .Nm
                     44: serves a similar purpose to the DOS program.
                     45: When called with no arguments, it prints the sector 0 partition table.
                     46: An example follows:
                     47:
                     48: .Bd -literal
                     49:        ******* Working on device /dev/rwd0d *******
                     50:        parameters extracted from in-core disklabel are:
                     51:        cylinders=769 heads=15 sectors/track=33 (495 blks/cyl)
                     52:
                     53:        parameters to be used for BIOS calculations are:
                     54:        cylinders=769 heads=15 sectors/track=33 (495 blks/cyl)
                     55:
                     56:        Warning: BIOS sector numbering starts with sector 1
                     57:        Information from DOS bootblock is:
                     58:        The data for partition 0 is:
1.3       cgd        59:        sysid 165,(NetBSD)
1.1       cgd        60:            start 495, size 380160 (185 Meg), flag 0
                     61:                beg: cyl 1/ sector 1/ head 0;
                     62:                end: cyl 768/ sector 33/ head 14
                     63:        The data for partition 1 is:
                     64:        sysid 164,(unknown)
                     65:            start 378180, size 2475 (1 Meg), flag 0
                     66:                beg: cyl 764/ sector 1/ head 0;
                     67:                end: cyl 768/ sector 33/ head 14
                     68:        The data for partition 2 is:
                     69:        <UNUSED>
                     70:        The data for partition 3 is:
                     71:        sysid 99,(ISC UNIX, other System V/386, GNU HURD or Mach)
                     72:            start 380656, size 224234 (109 Meg), flag 80
                     73:                beg: cyl 769/ sector 2/ head 0;
                     74:                end: cyl 197/ sector 33/ head 14
                     75: .Ed
                     76: .Pp
1.4       jtc        77: The disk is divided into three partitions that happen to fill the disk.
1.1       cgd        78: The second partition overlaps the end of the first.
                     79: (Used for debugging purposes)
                     80: .Bl -tag -width "cyl, sector and head"
                     81: .It Em "sysid"
1.3       cgd        82: is used to label the partition.  NetBSD reserves the
1.1       cgd        83: magic number 165 decimal (A5 in hex).
                     84: .It Em "start and size"
                     85: fields provide the start address
1.4       jtc        86: and size of a partition in sectors.
1.1       cgd        87: .It Em "flag 80"
                     88: specifies that this is the active partition.
                     89: .It Em "cyl, sector and head"
                     90: fields are used to specify the beginning address
1.4       jtc        91: and end address for the partition.
1.1       cgd        92: .It Em "Note:"
                     93: these numbers are calculated using BIOS's understanding of the disk geometry
                     94: and saved in the bootblock.
                     95: .El
                     96: .Pp
                     97: The flags
                     98: .Fl i
                     99: or
                    100: .Fl u
1.4       jtc       101: are used to indicate that the partition data is to be updated.
1.1       cgd       102: The
                    103: .Nm
                    104: program will enter a conversational mode.
                    105: This mode is designed not to change any data unless you explicitly tell it to.
                    106: .Nm
1.4       jtc       107: selects defaults for its questions to guarantee the above behavior.
1.1       cgd       108: .Pp
                    109: It displays each partition
                    110: and ask if you want to edit it.
                    111: If you say yes,
                    112: it will step through each field showing the old value
                    113: and asking for a new one.
                    114: When you are done with a partition,
                    115: .Nm
                    116: will display it and ask if it is correct.
                    117: .Nm
                    118: will then procede to the next entry.
                    119: .Pp
                    120: Getting the
                    121: .Em cyl, sector,
                    122: and
                    123: .Em head
                    124: fields correct is tricky.
                    125: So by default,
                    126: they will be calculated for you;
                    127: you can specify them if you choose.
                    128: .Pp
                    129: After all the partitions are processed,
                    130: you are given the option to change the
                    131: .Em active
                    132: partition.
                    133: Finally,
                    134: when the all the data for the first sector has been accumulated,
                    135: you are asked if you really want to rewrite sector 0.
                    136: Only if you answer yes,
                    137: will the data be written to disk.
                    138: .Pp
                    139: The difference between the
                    140: .Fl u
                    141: flag and
                    142: .Fl i
                    143: flag is that
                    144: the
                    145: .Fl u
                    146: flag just edits the fields as they appear on the disk.
                    147: While the
                    148: .Fl i
                    149: flag is used to "initialize" sector 0;
1.3       cgd       150: it will setup the last BIOS partition to use the whole disk for NetBSD;
1.1       cgd       151: and make it active.
                    152: .Sh NOTES
                    153: .Pp
                    154: The automatic calculation of starting cylinder etc. uses
                    155: a set of figures that represent what the BIOS thinks is the
                    156: geometry of the drive.
                    157: These figures are by default taken from the incore disklabel,
1.4       jtc       158: but the program initially gives you an opportunity to change them.
1.1       cgd       159: This allows the user to create a bootblock that can work with drives
                    160: that use geometry translation under the BIOS.
                    161: .Pp
                    162: If you hand craft your disk layout,
1.3       cgd       163: please make sure that the NetBSD partition starts on a cylinder boundary.
1.1       cgd       164: A number of decisions made later may assume this.
                    165: (This might not be necessary later.)
                    166: .Pp
                    167: Editing an existing partition will most likely cause you to
                    168: lose all the data in that partition.
                    169: .Pp
                    170: You should run this program interactively once or twice to see how it works.
                    171: This is completely safe as long as you answer the last question in the negative.
                    172: There are subtleties
                    173: that the program detects
                    174: that are not fully explained in this manual page.
                    175: .Sh SEE ALSO
                    176: .Xr disklabel 8
                    177: .Sh BUGS
                    178: One less now, but probably more

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