Subversion Repositories planix.SVN

.TH PREP 8

.SH NAME

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

.SH SYNOPSIS

.B disk/prep

[

.B -bcfnprw

]

[

.B -a

.I name

]...

[

.B -s

.I sectorsize

]

.I plan9partition

.PP

.B disk/fdisk

[

.B -abfprw

]

[

.B -s

.I sectorsize

]

.I disk

.PP

.B disk/format

[

.B -dfvx

]

[

.B -b

.I bootblock

]

[

.B -c

.I csize

]

[

.B -l

.I label

]

[

.B -r

.I nresrv

]

[

.B -t

.I type

]

.I disk

[

.IR file ...

]

.PP

.B disk/mbr

[

.B -9

]

[

.B -m

.I mbrfile

]

.I disk

.SH DESCRIPTION

A partition table is stored on a non-floppy disk to specify the division 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

.B 0x39

are Plan 9 partitions.

The names of PC partitions are chosen by convention from the type:

.BR dos ,

.BR 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).

.PP

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

.BI part " name start end" \fR,

where

.I start

and

.I 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.

.PP

The Plan 9 partition often contains a number of

conventionally named subpartitions.

They include:

.TF arenas

.TP

.B 9fat

A small FAT file system used to hold

configuration information

(such as

.B plan9.ini

and

.BR 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

.B -r

option to

.IR format .

.TP

.B arenas

A

.IR venti (8)

arenas partition.

.TP

.B bloom

A

.IR venti (8)

bloom-filter partition.

.TP

.B cache

A

.IR cfs (4)

file system cache.

.TP

.B fossil

A

.IR fossil (4)

file system.

.TP

.B fs

A

.IR kfs (4)

file system.

.TP

.B fscfg

A few-sector partition used to store an

.IR fs (3)

configuration.

.TP

.B isect

A

.IR venti (8)

index section.

.TP

.B nvram

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

.TP

.B other

A non-archived

.IR fossil (4)

file system.

.TP

.B swap

A

.IR swap (8)

swap partition.

.PD

.SS "fdisk and prep"

.I Fdisk

edits the PC partition table and is usually

invoked with a disk like

.B /dev/sdC0/data

as its argument, while

.I prep

edits the Plan 9 partition table

and is usually invoked with a disk partition

like

.B /dev/sdC0/plan9

as its argument.

.I Fdisk

works in units of disk ``cylinders'': the cylinder

size in bytes is printed when

.I fdisk

starts.

.I Prep

works in units of disk sectors, which are almost always 512 bytes.

.I Fdisk

and

.I prep

share most of their options:

.TF -a

.PD

.TP

.B -a

Automatically partition the disk.

.I 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),

.I fdisk

will mark the new partition active.

.IR Prep 's

.B -a

flag takes the name of a partition to create.

(See the list above for partition names.)

It can be repeated to specify a list of partitions to create.

If the disk is currently unpartitioned,

.I 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.

.TP

.B -b

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

.TP

.B -p

Print a sequence of commands that when sent to the disk device's

.B ctl

file

will bring the partition

table information kept by

the

.IR sd (3)

driver up to date.

Then exit.

.I 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 sectors by the partition's offset

within the disk.

Since

.I fdisk

operates on a table of unnamed partitions,

it assigns names based on the partition type

(e.g.,

.BR plan9 ,

.BR dos ,

.BR ntfs ,

.BR linux ,

.BR linuxswap )

and resolves collisions by appending a numbered suffix.

(e.g.,

.BR dos ,

.BR dos.1 ,

.BR dos.2 ).

.TP

.B -r

In the absence of the

.B -p

and

.B -w

flags,

.I prep

and

.I fdisk

enter an interactive partition editor;

the

.B -r

flag runs the editor in read-only mode.

.TP

.BI -s " sectorsize"

Specify the disk's sector size.

In the absence of this flag,

.I prep

and

.I fdisk

look for a disk

.B ctl

file and read it to find the disk's sector size.

If the

.B ctl

file cannot be found, a message is printed and

a sector size of 512 bytes is assumed.

.TP

.B -w

Write the partition table to the disk and exit.

This is useful when used in conjunction with

.B -a

or

.BR -b .

.PP

If neither the

.B -p

flag nor the

.B -w

flag is given,

.I prep

and

.I 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 secondary (or extended) partitions, arbitrarily

many of which may be chained together in place

of a primary partition.

Primary partitions are named

.BR p \fIn\fR,

secondary partitions

.BR s \fIn\fR.

The number of primary partitions plus number of contiguous chains of

secondary partitions cannot exceed four.

.PP

The commands are as follows.

In the descriptions, read ``sector'' as ``cylinder'' when using

.IR fdisk .

.TF ".\fI newdot

.PD

.TP

.B "a\fR \fIname\fR [ \fIstart\fR [ \fIend\fR ] ]"

Create a partition named

.I name

starting at sector offset

.I start

and ending at offset

.IR end .

The new partition will not be created if

it overlaps an extant partition.

If

.I start

or

.I end

are omitted,

.I prep

and

.I fdisk

will prompt for them.

In

.IR fdisk ,

the newly created partition has type

.RB `` PLAN9 ;''

to set a different type, use the

.B t

command (q.v.).

.I Start

and

.I end

may be expressions using the operators

.BR + ,

.BR - ,

.BR * ,

and

.BR / ,

numeric constants, and the

pseudovariables

.B .

and

.BR $ .

At the start of the program,

.B .

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

.B .

command.

When evaluating

.IR start ,

.B $

is set to one past the last disk sector.

When evaluating

.IR end ,

.B $

is set to the maximum value that

.I end

can take on without running off the disk

or into another partition.

Numeric constants followed by

.LR k ,

.LR m ,

.LR g ,

or

.LR t

(or upper-case equivalents)

are scaled to the respective size in kilo-, mega-, giga-, or tera-bytes.

Finally, the expression

.IB n %

evaluates to

.RI ( n × disksize )/100.

As examples,

.L "a . .+20%"

creates a new partition starting at

.B .

that takes up a fifth of the disk,

.L "a . .+21G"

creates a new partition starting at

.B .

that takes up 21 gigabytes (21×2\u\s-130\s0\d bytes),

and

.L "a 1000 $"

creates a new partition starting at

sector 1000 and

extending as far as possible.

.TP

.B ".\fR \fInewdot"

Set the value of the variable

.B .

to

.IR newdot ,

which is an arithmetic expression as described

in the discussion of the

.B a

command.

.TP

.BI d " name"

Delete the named partition.

.TP

.B h

Print a help message listing command synopses.

.TP

.B p

Print the disk partition table.

Unpartitioned regions are also listed.

The table consists of a number of lines containing

partition name, beginning and ending sectors,

and total size.

A

.B '

is prefixed to the names of partitions

whose entries have been modified but not written to disk.

.I Fdisk

adds to the end of each line a textual partition type,

and places a

.B *

next to the name of the active partition

(see the

.B A

command below).

.TP

.B P

Print the partition table in the format accepted by the disk's

.B ctl

file, which is also the format of the output of the

.B -p

option.

.TP

.B w

Write the partition table to disk.

.I 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),

.I prep

and

.I fdisk

will attempt to restore the partition table to

its former state.

.TP

.B q

Quit the program.

If the partition table has been modified but not written,

a warning is printed.

Typing

.B q

again will quit the program.

.PP

.I Fdisk

also has the following commands.

.TF "t \fR[\fI type \fR]

.PD

.TP

.BI A " name

Set the named partition active.

The active partition is the one whose boot block is used

when booting a PC from disk.

.TP

.B e

Print the names of empty slots in the partition table, i.e., the

valid names to use when creating a new partition.

.TP

.BI t " \fR[\fI type \fR]

Set the partition type.  If it is not given,

.I fdisk

will display a list of choices and then prompt for it.

.PD

.SS "format and pbs"

.I Format

prepares for use the disk partition or the floppy diskette in the file named

.IR disk ,

for example

.B /dev/sdC0/9fat

or

.BR /dev/fd0disk .

The options are:

.TP

.B -f

Do not physically format the disc. Used

to install a FAT file system on a

previously formatted disc. If

.I disk

is not a floppy device, this flag is a no-op.

.TP

.B -t

specify a density and type of disk to be prepared.

The possible

.I types

are:

.RS

.TP

.B 3½DD

3½" double density, 737280 bytes

.TP

.B 3½HD

3½" high density, 1474560 bytes

.TP

.B 5¼DD

5¼" double density, 368640 bytes

.TP

.B 5¼HD

5¼"  high density, 1146880 bytes

.TP

.B hard

fixed disk

.PD

.PP

The default when

.I disk

is a floppy drive is the highest possible on the device.

When

.I disk

is a regular file, the default is

.BR 3½HD .

When

.I disk

is an

.IR sd (3)

device, the default is

.BR hard .

.RE

.TP

.B -d

initialize a FAT file system on the

.IR disk .

.TP

.B -b

use the contents of

.I bootblock

as a bootstrap block

to be installed in sector 0.

.PD

.PP

The remaining options have effect only when

.B -d

is specified:

.TP

.B -c

use a FAT cluster size of

.I csize

sectors when creating the FAT.

.TP

.B -l

add a

.I label

when creating the FAT file system.

.TP

.BI -r

mark the first

.I nresrv

sectors of the partition as ``reserved''.

Since the first sector always contains the

FAT parameter block, this really marks

the

.IR nresrv -1

sectors starting at sector 1 as ``reserved''.

When formatting the

.B 9fat

partition,

.B -r

.B 2

should be used to jump over the partition table sector.

.PD

.PP

Again under

.BR -d ,

any

.I files

listed are added, in order,

to the root

directory of the FAT file system.  The files are

contiguously allocated.

If a file is named

.BR 9load ,

it will be created with the

.B SYSTEM

attribute set so that

.IR dossrv (4)

keeps it contiguous when modifying it.

.PP

.I Format

checks for a number of common mistakes; in particular,

it will refuse to format a

.B 9fat

partition unless

.B -r

is specified with

.I nresrv

larger than two.

It also refuses to format a raw

.IR sd (3)

partition that begins at offset zero in the disk.

(The beginning of the disk should contain an

.I fdisk

partition table with master boot record,

not a FAT file system or boot block.)

Both checks are disabled by the

.B -x

option.

The

.B -v

option prints debugging information.

.PP

The file

.B /386/pbs

is an example of a suitable

.I 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

.BR 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

.B /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.

.B /386/pbsraw

is suitable for CDs.

.SS mbr

.I Mbr

installs a new boot block in sector 0 (the master boot record)

of a disk such as

.BR /dev/sdC0/data .

If

.I 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

.IR format ,

which goes in sector 0 of a partition.

Typically, 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

program such as

.I 9load

(see

.IR 9boot (8)),

which then loads the operating system.

If MS-DOS or Windows is already installed

on your disk, the master boot record

already has a suitable boot block.

Otherwise,

.B /386/mbr

is an appropriate

.IR mbrfile .

It detects and uses LBA addressing when available

from the BIOS (the same could not

be done in the case of

.B pbs

due to space considerations).

If the

.I mbrfile

is not specified, a boot block is installed that

prints a message explaining that the disk is not bootable.

The

.B -9

option initialises the partition table to consist of one

.BR plan9

partition which spans the entire disc starting at the end of the

first track.

.SH EXAMPLES

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.

.IP

.EX

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

}

.EE

.PP

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

.IP

.EX

disk/format -b /386/pbs -df /dev/fd0disk \e

	/386/9load /tmp/plan9.ini /386/9pcf.gz

.EE

.PP

Initialize the blank disk

.BR /dev/sdC0/data .

.IP

.EX

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 \e

	/386/9load /386/9pcf /tmp/plan9.ini

.EE

.SH FILES

.TF /386/mbr.bootmgr

.TP

.B /386/mbr

.TP

.B /386/mbr.bootmgr

self-configuring `smart boot manager'

.SH SOURCE

.TF /n/sources/extra/bootmgr.tgz

.TP

.B /sys/src/cmd/disk/prep

.TP

.B /sys/src/boot/pc

.TP

.B /n/sources/extra/bootmgr.tgz

.I nasm

assembler source for

.B /386/mbr.bootmgr

.SH SEE ALSO

.IR floppy (3),

.IR sd (3),

.IR usb (4),

.IR 9boot (8),

.IR mk9660 (8),

.IR mkusbboot (8),

.IR partfs (8)

.SH BUGS

.I Format

can create FAT12 and FAT16

file systems, but not FAT32 file systems.

The boot block can only read from

FAT12 and FAT16 file systems.

.PP

If

.L "prep -p"

doesn't find a Plan 9 partition table,

it will emit commands to delete

.I all

extant partitions.

Similarly,

.L "fdisk -p"

will delete all partitions,

including

.LR data ,

if there are no partitions defined in the MBR.