prep man page on Plan9

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PREP(8)								       PREP(8)

       prep, fdisk, format, mbr - prepare disks, floppies and flashes

       disk/prep [ -bcfnprw ] [ -a name ]...  [ -s sectorsize ] plan9partition

       disk/fdisk [ -abfprw ] [ -s sectorsize ] disk

       disk/format  [  -dfvx ] [ -b bootblock ] [ -c csize ] [ -l label ] [ -r
       nresrv ] [ -t type ] disk [ file...  ]

       disk/mbr [ -9 ] [ -m mbrfile ] disk

       A partition table is stored on a non-floppy disk to specify  the	 divi‐
       sion  of	 the  physical	disk into a set of logical units.  On PCs, the
       partition table is stored at the end of the master boot record  of  the
       disk.   Partitions of type 0x39 are Plan 9 partitions.  The names of PC
       partitions are chosen by convention from the  type:  dos,  plan9,  etc.
       Second  and  subsequent partitions of the same type on a given disk are
       given unique names by appending a number (or a period and a  number  if
       the name already ends in a number).

       Plan 9 partitions (and Plan 9 disks on non-PCs) are themselves divided,
       using a textual partition table, called the Plan 9 partition table,  in
       the second sector of the partition (the first is left for architecture-
       specific boot data, such as PC boot blocks).  The table is  a  sequence
       of  lines  of  the format part name start end, where start and end name
       the starting and ending sector.	Sector 0 is the first  sector  of  the
       Plan  9 partition or disk, regardless of its position in a larger disk.
       Partition extents do not contain the ending sector, so a partition from
       0 to 5 and a partition from 5 to 10 do not overlap.

       The  Plan  9  partition often contains a number of conventionally named
       subpartitions.  They include:

       9fat   A small FAT file system used to hold  configuration  information
	      (such  as	 plan9.ini and plan9.nvr) and kernels.	This typically
	      begins in the first sector of the partition,  and	 contains  the
	      partition table as a ``reserved'' sector.	 See the discussion of
	      the -r option to format.

       arenas A venti(8) arenas partition.

       bloom  A venti(8) bloom-filter partition.

       cache  A cfs(4) file system cache.

       fossil A fossil(4) file system.

       fs     A kfs(4) file system.

       fscfg  A few-sector partition used to store an fs(3) configuration.

       isect  A venti(8) index section.

       nvram  A one-sector partition used to simulate non-volatile RAM on PCs.

       other  A non-archived fossil(4) file system.

       swap   A swap(8) swap partition.

   fdisk and prep
       Fdisk edits the PC partition table and is usually invoked with  a  disk
       like /dev/sdC0/data as its argument, while prep edits the Plan 9 parti‐
       tion  table  and	 is  usually  invoked  with  a	disk  partition	  like
       /dev/sdC0/plan9 as its argument.	 Fdisk works in units of disk ``cylin‐
       ders'': the cylinder size in bytes is printed when fdisk starts.	  Prep
       works  in  units	 of  disk  sectors, which are almost always 512 bytes.
       Fdisk and prep share most of their options:

       -a     Automatically partition the disk.	 Fdisk will create  a  Plan  9
	      partition	 in the largest unused area on the disk, doing nothing
	      if a Plan 9 partition already exists.  If no other partition  on
	      the  disk	 is marked active (i.e. marked as the boot partition),
	      fdisk will mark the new partition active.	 Prep's -a flag	 takes
	      the name of a partition to create.  (See the list above for par‐
	      tition names.)  It can be repeated to specify a list  of	parti‐
	      tions  to	 create.  If the disk is currently unpartitioned, prep
	      will create the named partitions on the disk, attempting to  use
	      the  entire disk in a sensible manner.  The partition names must
	      be from the list given above.

       -b     Start with a blank disk, ignoring any extant partition table.

       -p     Print a sequence of commands that when sent to the disk device's
	      ctl  file will bring the partition table information kept by the
	      sd(3) driver up to date.	Then exit.  Prep will check to see  if
	      it  is being called with a disk partition (rather than an entire
	      disk) as its argument; if so, it will translate the printed sec‐
	      tors  by	the  partition's  offset within the disk.  Since fdisk
	      operates on a table of  unnamed  partitions,  it	assigns	 names
	      based on the partition type (e.g., plan9, dos, ntfs, linux, lin‐
	      uxswap) and resolves collisions by appending a numbered  suffix.
	      (e.g., dos, dos.1, dos.2).

       -r     In  the  absence of the -p and -w flags, prep and fdisk enter an
	      interactive partition editor; the -r flag	 runs  the  editor  in
	      read-only mode.

       -s sectorsize
	      Specify  the  disk's  sector size.  In the absence of this flag,
	      prep and fdisk look for a disk ctl file and read it to find  the
	      disk's  sector size.  If the ctl file cannot be found, a message
	      is printed and a sector size of 512 bytes is assumed.

       -w     Write the partition table to the disk and exit.  This is	useful
	      when used in conjunction with -a or -b.

       If  neither  the -p flag nor the -w flag is given, prep and fdisk enter
       an interactive partition editor that operates on named partitions.  The
       PC  partition table distinguishes between primary partitions, which can
       be listed in the boot sector at the beginning of	 the  disk,  and  sec‐
       ondary  (or  extended)  partitions,  arbitrarily	 many  of which may be
       chained together in place of a primary partition.   Primary  partitions
       are  named  pn,	secondary partitions sn.  The number of primary parti‐
       tions plus number of contiguous chains of secondary  partitions	cannot
       exceed four.

       The  commands  are as follows.  In the descriptions, read ``sector'' as
       ``cylinder'' when using fdisk.

       a name [ start [ end ] ]
	      Create a partition named name starting at	 sector	 offset	 start
	      and ending at offset end.	 The new partition will not be created
	      if it overlaps an extant partition.  If start or end  are	 omit‐
	      ted,  prep  and fdisk will prompt for them.  In fdisk, the newly
	      created partition has type ``PLAN9;'' to set a  different	 type,
	      use  the	t  command  (q.v.).   Start and end may be expressions
	      using the operators +, -, *, and /, numeric constants,  and  the
	      pseudovariables  .   and	$.  At the start of the program, .  is
	      set to zero; each time a partition is created, it is set to  the
	      end  sector of the new partition.	 It can also be explicitly set
	      using the .  command.  When evaluating start, $ is  set  to  one
	      past the last disk sector.  When evaluating end, $ is set to the
	      maximum value that end can take on without running off the  disk
	      or into another partition.  Numeric constants followed by or (or
	      upper-case equivalents) are scaled to  the  respective  size  in
	      kilo-,  mega-, giga-, or tera-bytes.  Finally, the expression n%
	      evaluates to (n×disksize)/100.  As examples, creates a new  par‐
	      tition starting at .  that takes up a fifth of the disk, creates
	      a new partition starting	at  .	that  takes  up	 21  gigabytes
	      (21×230  bytes),	and creates a new partition starting at sector
	      1000 and extending as far as possible.

       . newdot
	      Set the value of the variable .  to newdot, which is  an	arith‐
	      metic  expression	 as  described in the discussion of the a com‐

       d name Delete the named partition.

       h      Print a help message listing command synopses.

       p      Print the disk partition table.  Unpartitioned regions are  also
	      listed.  The table consists of a number of lines containing par‐
	      tition name, beginning and ending sectors, and total size.  A  '
	      is  prefixed  to the names of partitions whose entries have been
	      modified but not written to disk.	 Fdisk adds to the end of each
	      line  a  textual partition type, and places a * next to the name
	      of the active partition (see the A command below).

       P      Print the partition table in the format accepted by  the	disk's
	      ctl  file,  which	 is  also  the	format of the output of the -p

       w      Write the partition table to disk.  Prep will  also  inform  the
	      kernel  of  the changed partition table.	The write will fail if
	      any programs have any of the disk's  partitions  open.   If  the
	      write  fails (for this or any other reason), prep and fdisk will
	      attempt to restore the partition table to its former state.

       q      Quit the program.	 If the partition table has been modified  but
	      not written, a warning is printed.  Typing q again will quit the

       Fdisk also has the following commands.

       A name Set the named partition active.  The active partition is the one
	      whose boot block is used when booting a PC from disk.

       e      Print the names of empty slots in the partition table, i.e., the
	      valid names to use when creating a new partition.

       t [ type ]
	      Set the partition type.  If it is not given, fdisk will  display
	      a list of choices and then prompt for it.

   format and pbs
       Format  prepares	 for  use the disk partition or the floppy diskette in
       the file named disk, for example /dev/sdC0/9fat or  /dev/fd0disk.   The
       options are:

       -f     Do  not  physically  format the disc. Used to install a FAT file
	      system on a previously formatted disc. If disk is not  a	floppy
	      device, this flag is a no-op.

       -t     specify a density and type of disk to be prepared.  The possible
	      types are:

	      3½DD   3½" double density, 737280 bytes

	      3½HD   3½" high density, 1474560 bytes

	      5¼DD   5¼" double density, 368640 bytes

	      5¼HD   5¼"  high density, 1146880 bytes

	      hard   fixed disk

	      The default when disk is a floppy drive is the highest  possible
	      on  the  device.	 When  disk  is a regular file, the default is
	      3½HD.  When disk is an sd(3) device, the default is hard.

       -d     initialize a FAT file system on the disk.

       -b     use the contents	of  bootblock  as  a  bootstrap	 block	to  be
	      installed in sector 0.

       The remaining options have effect only when -d is specified:

       -c     use a FAT cluster size of csize sectors when creating the FAT.

       -l     add a label when creating the FAT file system.

       -r     mark  the first nresrv sectors of the partition as ``reserved''.
	      Since the first sector always contains the FAT parameter	block,
	      this  really  marks the nresrv-1 sectors starting at sector 1 as
	      ``reserved''.  When formatting the 9fat partition, -r  2	should
	      be used to jump over the partition table sector.

       Again  under  -d,  any  files  listed  are added, in order, to the root
       directory of the FAT file system.  The  files  are  contiguously	 allo‐
       cated.	If  a  file is named 9load, it will be created with the SYSTEM
       attribute set so that dossrv(4) keeps it contiguous when modifying it.

       Format checks for a number of common mistakes; in particular,  it  will
       refuse  to  format  a 9fat partition unless -r is specified with nresrv
       larger than two.	 It also refuses to format a raw sd(3) partition  that
       begins  at  offset zero in the disk.  (The beginning of the disk should
       contain an fdisk partition table with master boot  record,  not	a  FAT
       file system or boot block.)  Both checks are disabled by the -x option.
       The -v option prints debugging information.

       The file /386/pbs is an example of a suitable  bootblock	 to  make  the
       disk  a	boot  disk.   It  gets loaded by the BIOS at 0x7C00, reads the
       first sector of the root directory into address 0x7E00, and looks for a
       directory entry named 9LOAD.  If it finds such an entry, it uses single
       sector reads to load the file into address 0x10000 and  then  jumps  to
       the loaded file image.  The file /386/pbslba is similar, but because it
       uses LBA addressing (not supported by older BIOSes), it can access more
       than the first 8.5GB of the disk.  /386/pbsraw is suitable for CDs.

       Mbr installs a new boot block in sector 0 (the master boot record) of a
       disk such as /dev/sdC0/data.  If mbrfile contains more than one	sector
       of  `boot  block',  the rest will be copied into the first track of the
       disk, if it fits.  This boot block should not be confused with the boot
       block  used  by	format,	 which goes in sector 0 of a partition.	 Typi‐
       cally, the boot block in the master boot record scans the PC  partition
       table  to find an active partition and then executes the boot block for
       that partition.	The partition boot block then loads a  bootstrap  pro‐
       gram  such as 9load (see 9boot(8)), which then loads the operating sys‐
       tem.  If MS-DOS or Windows is already installed on your disk, the  mas‐
       ter boot record already has a suitable boot block.  Otherwise, /386/mbr
       is an appropriate mbrfile.  It detects and  uses	 LBA  addressing  when
       available  from the BIOS (the same could not be done in the case of pbs
       due to space considerations).  If the mbrfile is not specified, a  boot
       block  is  installed  that prints a message explaining that the disk is
       not bootable.  The -9 option initialises the partition table to consist
       of  one plan9 partition which spans the entire disc starting at the end
       of the first track.

       Initialize the kernel disk driver with the partition  information  from
       the  FAT boot sectors.  If Plan 9 partitions exist, pass that partition
       information as well.

	      for(disk in /dev/sd??) {
		   if(test -f $disk/data && test -f $disk/ctl)
			disk/fdisk -p $disk/data >$disk/ctl
		   for(part in $disk/plan9*)
			if(test -f $part)
			     disk/prep -p $part >$disk/ctl

       Create a Plan 9 boot floppy on a previously formatted diskette.

	      disk/format -b /386/pbs -df /dev/fd0disk \
		   /386/9load /tmp/plan9.ini /386/9pcf.gz

       Initialize the blank disk /dev/sdC0/data.

	      disk/mbr -m /386/mbr /dev/sdC0/data
	      disk/fdisk -baw /dev/sdC0/data
	      disk/prep -bw -a^(9fat nvram fossil cache swap) /dev/sdC0/plan9
	      disk/format -b /386/pbslba -d -r 2 /dev/sdC0/9fat \
		   /386/9load /386/9pcf /tmp/plan9.ini


	      self-configuring `smart boot manager'



	      nasm assembler source for /386/mbr.bootmgr

       floppy(3), sd(3), usb(4), 9boot(8), mk9660(8), mkusbboot(8), partfs(8)

       Format can create FAT12 and FAT16 file systems, but not FAT32 file sys‐
       tems.  The boot block can only read from FAT12 and FAT16 file systems.

       If  doesn't  find  a  Plan  9 partition table, it will emit commands to
       delete all extant partitions.  Similarly, will delete  all  partitions,
       including if there are no partitions defined in the MBR.

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                         \ \| |/ / \ \| |/ / \ \| |/ /  
                          \ \ / /   \ \ / /   \ \ / /   
                           \   /     \   /     \   /    
                            \_/       \_/       \_/ 
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