 @@ -1,678 +1,678 @@
-.\"	$NetBSD: fdisk.8,v 1.86 2016/09/11 03:35:08 sevan Exp $
+.\"	$NetBSD: fdisk.8,v 1.87 2017/01/27 10:12:05 abhinav Exp $
 .\"
 .Dd September 11, 2016
 .Dt FDISK 8
 .Os
 .Sh NAME
 .Nm fdisk
 .Nd MS-DOS partition maintenance program
 .Sh SYNOPSIS
 .Nm
 .Op Fl aBFfIiSuv
 .Oo
 .Fl 0 | 1 | 2 | 3 | E Ar number
 .Op Fl s Oo Ar id Oc Ns Oo / Ns Oo Ar start Oc Ns Oo / Ns Oo Ar size Oc Ns Oo / Ns Oo Ar bootmenu Oc Oc Oc Oc
 .Oc
 .Op Fl r Ar file | Fl w Ar file
 .Op Fl A Ar ptn_alignment Ns Bq Ar /ptn_0_offset
 .Op Fl b Ar cylinders/heads/sectors
 .Op Fl c Ar bootcode
 .Op Fl T Ar disktype
 .Op Fl t Ar disktab
 .Op Fl z Ar sectorsize
 .Op Ar device
 .Nm
 .Fl l
 .Sh DESCRIPTION
 The
 .Nm
 program is used to display or update the
 .Em "master boot record"
 or
 .Em MBR
 in the first sector (sector 0)
 of a disk that uses the MBR style of partitioning.
 The following
 .Nx
 ports use this style of disk partitioning:
 amd64, arc, bebox, cobalt, hpcarm, hpcmips, hpcsh, i386, macppc,
 mvmeppc, netwinder, ofppc, playstation2, and prep.
 .Pp
 The MBR contains bootable code, a partition table,
 an indication of which partition is
 .Sq active ,
 and (optionally, depending on the boot code) a menu
 for selecting a partition to be booted.
 There can be at most 4 partitions defined in sector 0,
 one of which can be an extended
 partition which can be split into any number of sub-partitions (then called
 logical partitions).
 .Pp
 The boot code in the MBR is usually invoked by the BIOS or firmware,
 and the MBR passes control to the next stage boot code
 stored in the first sector of the partition to be booted
 (the
 .Em "partition boot record"
 or
 .Em PBR ) .
 .Pp
 After booting,
 .Nx
 does not use the partitioning done by
 .Nm ,
 instead it uses a
 .Nx
 disklabel saved in sector 1 of the
 .Nx
 partition.
 See
 .Xr mbrlabel 8
 for a way of using information from the MBR
 to construct a
 .Nx
 disklabel.
 .Pp
 The standard MBR boot code will only boot the
 .Sq active
 partition.
 However,
 .Nx
 contains additional boot programs which allow the user to
 interactively select which of the partitions to boot.
 The
 .Sq mbr_ext
 code will also boot
 .Nx
 from an extended partition but will not work on old systems that do not
 support LBA reads, the
 .Sq mbr_com0
 and
 .Sq mbr_com0_9600
 will read and write from a serial port.
 At the start the
 .Nm
 program will determine whether the disk sector 0 is valid as a boot sector.
 (This is determined by checking the magic number.)
 If not,
 .Nm
 will initialise the boot code as well as the partition table.
 During this, all four partitions will be marked empty.
 .Pp
 The flags
 .Fl a ,
 .Fl i
 or
 .Fl u
 are used to indicate that the partition data is to be updated.
 The
 .Nm
 program will enter an interactive conversational mode.
 This mode is designed not to change any data unless you explicitly tell it to;
 .Nm
 selects defaults for its questions to guarantee that behaviour.
 .Pp
 If partition data is going to be updated and the disk carries GUID Partition
 Tables,
 .Nm
 will remove both primary and backup GPT headers from the disk.
 See
 .Xr gpt 8
 for information on how to manipulate GUID Partition Tables.
 .Pp
 .Nm
 will calculate the correct
 .Em cylinder ,
 .Em head ,
 and
 .Em sector
 values for any partition you edit.
 If you specify
 .Fl v
 you will be asked whether you want to specify them yourself.
 .Pp
 Finally, when all the data for the first sector has been accumulated,
 .Nm
 will ask if you really want to write the new partition table.
 Only if you reply affirmatively to this question will
 .Nm
 write anything to the disk.
 .Pp
 Available options:
 .Bl -tag -width Ds
 .It Fl 0
 Specify partition slot 0 to be printed or updated.
 .It Fl 1
 Specify partition slot 1 to be printed or updated.
 .It Fl 2
 Specify partition slot 2 to be printed or updated.
 .It Fl 3
 Specify partition slot 3 to be printed or updated.
 .It Fl A Ar ptn_alignment Ns Bq Ar /ptn_0_offset
 Specify the alignment for all partitions and optionally the offset for the
 first partition of the disk and of logical partitions.
 If
 .Ar ptn_alignment
 is specified and
 .Ar ptn_0_offset
 is not specified, then the offset is set to the alignment.
 If
 .Fl A
 is not specified, then the alignment of the first partition is inspected.
 If it ends on a 2048 sector boundary, then the alignment is set to 2048,
 if the start is a power of 2 less than, or equal to 2048 then the offset
 is set to the start sector.
 If the first partition is not defined then the alignment and offset for disks
 larger than 128GB is set to 2048 (1MB).
 In all other cases the alignment default to a cylinder
 and the offset to a track (both using the BIOS geometry).
 The 1MB alignment is the same as that used by recent windows versions.
 .It Fl a
 Change the active partition.
 In interactive mode this question will be asked after the partitions
 have been processed.
 .It Fl B
 On an i386 or amd64 system, interactively update the boot selector settings.
 (The boot selector permits the user to interactively select the boot
 partition, and thus which operating system is run, at system boot time; see
 .Xr mbr 8
 for more information.)
 .It Fl b Ar cylinders/heads/sectors
 Specify the BIOS geometry parameters for
 .Ar cylinders ,
 .Ar heads ,
 and
 .Ar sectors .
 It is used only in conjunction with the
 .Fl u
 flag.
 If not specified the BIOS geometry will be obtained using sysctl (i386 and
-amd64) or by solving the simultaenous equations from the existing partition
+amd64) or by solving the simultaneous equations from the existing partition
 information.
 If that fails then either the geometry from the disklabel or 63 sectors and
 heads is used.
 For modern disks larger than about 8GB, and where the BIOS is configured
 to use LBA-Assisted translation, a setting of
 .Fl b Ar 1023/255/63
 is likely to work.
 .\" see http://web.inter.nl.net/hcc/J.Steunebrink/bioslim.htm#LBA
 .\" for a table of C/H/S values used in LBA-Assisted translation mode
 .It Fl c Ar bootcode
 Specify the filename that
 .Nm
 should read the bootcode from.
 If the name of a directory is specified, then
 .Nm
 will look for files with the default names in that directory.
 The default is to read from
 .Pa /usr/mdec/mbr ,
 .Pa /usr/mdec/mbr_bootsel
 or
 .Pa /usr/mdec/mbr_ext
 depending on whether
 .Ar bootmenu
 was specified for any partitions
 on an i386 machine, and leave the bootcode empty for other
 machines.
 .It Fl E Ar number
 Specify logical partition
 .Ar number
 to be printed or updated.
 If the specified logical partition does not exist on updating partition data
 an additional logical partition will be created.
 .It Fl F
 Indicate that
 .Ar device
 is a regular file.
 Unless the geometry of
 .Ar device
 is told to
 .Nm
 by
 .Fl T Ar disktype ,
 .Nm
 will count the 512-byte sectors in
 .Ar device
 and produce a fake geometry.
 If
 .Ar device
 is a regular file,
 .Fl F
 will be used implicitly.
 .It Fl f
 Run
 .Nm
 in a non-interactive mode.
 In this mode, you can only change the disk parameters by using the
 .Fl b
 flag.
 This is provided only so scripts or other programs may use
 .Nm
 as part of an automatic installation process.
 .Pp
 Using the
 .Fl f
 flag with
 .Fl u
 makes it impossible to specify the starting and ending
 .Ar cylinder ,
 .Ar head ,
 and
 .Ar sector
 fields
 .Pq only Ar start No and Ar size No can be specified by Fl s No option .
 They will be automatically computed using the BIOS geometry.
 .It Fl I
 Ignore errors from overlapping partitions.
 Some devices (cameras CHDK) require overlapping partitions to support
 bigger than 4GB cards.
 The
 .Fl I
 flag ignores overlapping error checks and does not fix them, allowing these
 incorrect configurations to be used.
 .It Fl i
 Explicitly request initialisation of the master boot code
 (similar to what
 .Ic fdisk /mbr
 does under
 .Tn MS-DOS ) ,
 even if the magic number in the first sector is ok.
 The partition table is left alone by this (but see above).
 .It Fl l
 Lists known
 .Em sysid
 values and exit.
 .It Fl r Ar file
 Read the boot record from file
 .Ar file
 instead of the specified disk.
 The geometry information used is still that of the disk volume.
 Any changes are written back to the file.
 .It Fl S
 When used with no other flags print a series of
 .Pa /bin/sh
 commands for setting variables to the partition information.
 This could be used by installation scripts.
 .It Fl s Oo Ar id Oc Ns Oo / Ns Oo Ar start Oc Ns Oo / Ns Oo Ar size Oc Ns Oo / Ns Oo Ar bootmenu Oc Oc Oc Oc
 Specify the partition
 .Ar id ,
 .Ar start ,
 .Ar size ,
 and
 .Ar bootmenu .
 If the optional arguments are not provided, they stay as before or
 use the same defaults as the interactive mode, if new.
 This flag requires the use of a partition selection flag
 .Pq Fl 0 , 1 , 2 , 3 , No or Fl E Ar number .
 .It Fl T Ar disktype
 Use the disklabel
 .Ar disktype
 instead of the disklabel on
 .Ar device .
 .It Fl t Ar disktab
 Read
 .Ar disktype
 from the named
 .Xr disktab 5
 file instead of from
 .Pa /etc/disktab .
 .It Fl u
 Update partition data, including
 .Em id , start , No and Em size .
 Unless
 .Fl f
 option
 .Pq non-interactive mode
 is specified,
 .Nm
 will display the partitions and interactively ask which one you want to edit.
 .Nm
 will step through each field showing the old value and asking for a new one.
 The
 .Em start
 and
 .Em size
 can be specified in blocks (NN),
 cylinders (NNc or NNcyl),
 megabytes (NNm or NNMB),
 or gigabytes (NNg or NNGB), values in megabytes and gigabytes
 will be rounded to the nearest cylinder boundary.
 The
 .Em size
 may be specified as
 .Em $
 in which case the partition will extend to the end of the available free space.
 .Pp
 In a non-interactive mode
 .Pq specified by Fl f No option ,
 partition data should be specified by
 .Fl s
 option.
 A partition selection option
 .Pq Fl 0 , 1 , 2 , 3 , No or Fl E Ar number
 should also be specified to select a partition slot to be updated.
 .Pp
 .Nm
 will not allow you to create partitions which overlap.
 If
 .Fl u
 and
 .Fl s
 are specified in a non-interactive mode
 then the details of the specified partition will be changed.
 Any other partitions which overlap the requested part of the disk will be
 silently deleted.
 .Pp
 If
 .Em bootmenu
 is specified for any partition
 .Nm
 will determine whether the installed boot code supports the bootselect code,
 if it does not you will be asked whether you want to install the required
 boot code.
 To remove a
 .Em bootmenu
 label, simply press
 .Aq space
 followed by
 .Aq return .
 .It Fl v
 Be more verbose, specifying
 .Fl v
 more than once may increase the amount of output.
 .Pp
 Using
 .Fl v
 with
 .Fl u
 allows the user to change more parameters than normally permitted.
 .It Fl w Ar file
 Write the modified partition table to file
 .Ar file
 instead of the disk.
 .It Fl z Ar sectorsize
 Specify a sector size other than 512, for devices that only
 support larger sector sizes.
 The sector size needs to be a power of two greater than 512.
 .El
 .Pp
 When called with no arguments, it prints the partition table.
 An example follows:
 .Bd -literal
     Disk: /dev/rwd0d
     NetBSD disklabel disk geometry:
     cylinders: 16383, heads: 16, sectors/track: 63 (1008 sectors/cylinder)
     total sectors: 40032696
     BIOS disk geometry:
     cylinders: 1023, heads: 255, sectors/track: 63 (16065 sectors/cylinder)
     total sectors: 40032696
     Partition table:
 : NetBSD (sysid 169)
 	bootmenu: net 1.5.
 	start 4209030, size 8289540 (4048 MB, Cyls 262-778), Active
 : Primary DOS with 32 bit FAT (sysid 11)
 	bootmenu: win98
 	start 63, size 4208967 (2055 MB, Cyls 0-262)
 : NetBSD (sysid 169)
 	bootmenu: current
 	start 32515560, size 7517136 (3670 MB, Cyls 2024-2491/234/40)
 : Ext. partition - LBA (sysid 15)
 	start 12498570, size 20016990 (9774 MB, Cyls 778-2024)
     Extended partition table:
     E0: NetBSD (sysid 169)
 	bootmenu: test
 	start 12498633, size 12305727 (6009 MB, Cyls 778-1544)
     E1: Primary DOS with 32 bit FAT (sysid 11)
 	start 24804423, size 4096512 (2000 MB, Cyls 1544-1799)
     E2: Primary DOS with 32 bit FAT (sysid 11)
 	start 28900998, size 3614562 (1765 MB, Cyls 1799-2024)
     Bootselector enabled, infinite timeout.
     First active partition: 0
 .Ed
 .Pp
 This example disk is divided into four partitions, the last of which is
 an extended partition.
 The logical partitions of the extended partition are also shown.
 In this case there is no free space in either the disk or in the extended
 partition.
 .Pp
 The various fields in each partition entry are:
 .Bd -filled -offset 4n -compact
 .Em ptn_number : id_name
 (sysid
 .Em id_number )
 .Ed
 .Bd -filled -offset 8n -compact
 bootmenu:
 .Em bootmenu
 .br
 start
 .Em start ,
 size
 .Em size ( MB
 MB, Cyls
 .Em first Ns No - Ns Em next )
 .Op , Active
 .Ed
 .Bl -tag -width "bootmenu"
 .It Em ptn_number
 is the number of the partition.
 .It Em id_name
 is the name of the filesystem type or operating system that uses this partition.
 .It Em id_number
 is the number that identifies the partition type.
 decimal is used for
 .Nx
 partitions,
 decimal to create an extended partition
 and 0 to mark a partition as unused.
 Use
 .Nm
 .Fl l
 to list the known partition types.
 .It Em bootmenu
 is the menu prompt output by the interactive boot code for this partition.
 This line is omitted if the prompt is not defined.
 .It Em start , Em size
 are the start address and size of the partition in sectors.
 .It Em MB
 is the size of the partition in megabytes.
 .It Em first , Em next
 are the bounds of this partition displayed as cylinder/head/sector.
 If the partition starts (or ends) on a cylinder boundary the head and
 sector values are omitted.
 If
 .Fl v
 is not specified the start of logical partitions and the first partition
 on the disk are rounded down to include the mandatory red tape in the
 preceding track.
 .It Active
 is output if this is the active partition.
 .El
 .Pp
 If the
 .Fl v
 flag is specified, the beginning and end of each partition are also
 displayed as follows:
 .Bd -filled -offset 4n -compact
 beg: cylinder
 .Em cylinder ,
 head
 .Em head ,
 sector
 .Em sector
 .br
 end: cylinder
 .Em cylinder ,
 head
 .Em head ,
 sector
 .Em sector
 .Ed
 .Bl -tag -width "bootmenu"
 .It Em "cylinder" , Em "head" , Em "sector"
 are the beginning or ending address of a partition.
 .Pp
 .Em "Note:"
 these numbers are read from the bootblock, so are the values calculated
 by a previous run of
 .Nm .
 .El
 .Pp
 .Nm
 attempts to check whether each partition is bootable,
 by checking the magic number and some other characteristics
 of the first sector of each partition (the PBR).
 If the partition does not appear to be bootable,
 .Nm
 will print a line containing
 .Dq "PBR is not bootable"
 followed by an error message.
 If the partition is bootable, and if the
 .Fl v
 flag is specified,
 .Nm
 will print
 .Dq "PBR appears to be bootable" .
 If the
 .Fl v
 flag is specified more than once,
 .Nm
 will print the heading
 .Dq "Information from PBR:"
 followed by one or more lines of information gleaned from the PBR;
 this additional information may be incorrect or misleading,
 because different operating systems use different PBR formats.
 Note that, even if no errors are reported, an attempt to boot
 from the partition might fail.
 .Nx
 partitions may be made bootable using
 .Xr installboot 8 .
 .Sh NOTES
 This program is only available (and useful) on systems with PC-platform-style
 MBR partitioning.
 .Pp
 Traditionally the partition boundaries should be on cylinder boundaries
 using the BIOS geometry, with the exception of the first partition,
 which traditionally begins in the second track of the first cylinder
 (cylinder 0, head 1, sector 1).
 Although the BIOS geometry is typically different from the geometry
 reported by the drive, neither will match the actual physical geometry
 for modern disks (the actual geometry will vary across the disk).
 Keeping the partition boundaries on cylinder boundaries makes partitioning
 a driver easier as only relatively small numbers need be entered.
 .Pp
 The automatic calculation of the starting cylinder and
 other parameters uses
 a set of figures that represent what the BIOS thinks is the
 geometry of the drive.
 The default values should be correct for the system on which
 .Nm
 is run; however, if you move the disk to a different system, the
 BIOS of that system might use a different geometry translation.
 .Pp
 If you run the equivalent of
 .Nm
 on a different operating system then the
 .Ar bootmenu
 strings associated with extended partitions may be lost.
 .Pp
 Editing an existing partition is risky, and may cause you to
 lose all the data in that partition.
 .Pp
 You should run this program interactively once or twice to see how it works.
 This is completely safe as long as you answer the last question in the negative.
 You can also specify
 .Fl w Ar file
 to write the output to a file and later specify
 .Fl r Ar file
 to read back the updated information.
 This can be done without having write access to the disk volume.
 .Sh FILES
 .Bl -tag -width /usr/mdec/mbrxxxxxxxx -compact
 .It Pa /usr/mdec/mbr
 Default location of i386 bootcode
 .It Pa /usr/mdec/mbr_bootsel
 Default location of i386 bootselect code
 .It Pa /usr/mdec/mbr_ext
 Default location of i386 bootselect for extended partitions (i.e., NetBSD on
 logical partitions)
 .El
 .Sh EXAMPLES
 Update MBR partition data of
 .Pa /dev/rwd0d
 in interactive mode:
 .Pp
 .Dl Ic fdisk -u /dev/rwd0d
 .Pp
 Change active MBR partition of
 .Pa /dev/rwd0d
 in interactive mode:
 .Pp
 .Dl Ic fdisk -a /dev/rwd0d
 .Pp
 Install MBR bootcode
 .Pa /usr/mdec/mbr_bootsel
 into
 .Pa /dev/rwd0d :
 .Pp
 .Dl Ic fdisk -c /usr/mdec/mbr_bootsel /dev/rwd0d
 .Pp
 Set MBR partition data for slot 0 of
 .Pa /dev/rwd0d
 specifying values without prompt:
 .Pp
 .Dl Ic fdisk -f -u -0 -s 169/63/2097089 /dev/rwd0d
 .Pp
 Make partition slot 0 of
 .Pa /dev/rwd0d
 active without prompt:
 .Pp
 .Dl Ic fdisk -f -a -0 /dev/rwd0d
 .Pp
 Initialize and create MBR partition data using bootcode
 .Pa destdir/usr/mdec/mbr
 without prompt against 1GB disk image file
 .Pa diskimg :
 .Pp
 .Dl Ic fdisk -f -i -b 130/255/63 -c destdir/usr/mdec/mbr -F diskimg
 .Pp
 Create MBR partition data for slot 0 which has an active
 .Nx
 partition using whole disk without prompt against 1GB disk image file
 .Pa diskimg :
 .Pp
 .Dl Ic fdisk -f -a -u -0 -s 169/63/2097089 -F diskimg
 .Sh SEE ALSO
 .Xr disktab 5 ,
 .Xr boot 8 ,
 .Xr disklabel 8 ,
 .Xr gpt 8 ,
 .Xr installboot 8 ,
 .Xr mbr 8 ,
 .Xr mbrlabel 8
 .Sh HISTORY
 A version of
 .Nm
 first appeared in the Mach Operating System.
 It was subsequently ported to
 .Bx 386 .
 .Sh AUTHORS
 .An -nosplit
 .Nm
 for Mach Operating System was written by
 .An Robert Baron Aq Mt rvb@cs.cmu.edu .
 It was ported to
 .Bx 386
 by
 .An Julian Elischer Aq Mt julian@tfs.com .
 .Sh BUGS
 The word
 .Sq partition
 is used to mean both an MBR partition and a
 .Nx
 partition, sometimes in the same sentence.
 .Pp
 There are subtleties that the program detects that are not explained in
 this manual page.