PREP(8) PREP(8)
NAME
prep, format - prepare hard and floppy diskettes
SYNOPSIS
disk/prep [ -ra ] special [ type ]
disk/format [ -t type ] [ -f ] [ -d ] [ -b bfile ] [ -c
csize ] [ -l label ] drive [ files ... ]
DESCRIPTION
A partition table is stored on a hard disk to specify the
division of the physical disk into a set of logical units.
On Plan 9 the partition table is a list of triples: name,
starting sector, and ending sector. The kernel fabricates
the first two partitions, disk and partition; the disk par-
tition records the starting and ending sectors for the whole
disk, and the partition partition, typically the last sector
on the disk, holds the partition table itself.
Special is the maximal prefix of names of the logical units
on the disk, for example #w/hd0. Prep reads and prints the
associated partition table and then enters a simple interac-
tive mode to control editing the table.
The options are:
-r (read only) prohibits writing the table on disk.
-a automatically create default partitions if no partition
table already exists. These include partitions for
DOS, a boot kernel, an NVRAM substitute, a kfs(4) file
system, and, if room remains, a swap partition.
Format prepares for use the floppy diskette in the disk file
named drive, for example /dev/fd0disk. The options are:
-f Do not physically format the disc. Used to install an
MS-DOS filesystem on a previously formatted disc. With
this option, drive can be a plain file.
-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
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PREP(8) PREP(8)
The default is the highest possible on the device,
unless -f is used, in which case the default is 3½HD.
-d add MS-DOS parameter block, file access table (FAT),
and root directory to the start of the floppy.
The remaining options have effect only when -d is specified:
-b use the contents of bfile as the bootstrap block
installed in sector 0.
-c use a DOS cluster size of csize sectors when creating
the DOS FAT.
-l add a label when creating the DOS parameter block.
Again under -d, any files listed are added, in order, to the
root directory of the MS-DOS filesytem. The files are con-
tiguously allocated and created with the READONLY attribute
set.
The file /sys/src/boot/pc/bb is an example of a suitable
bfile to make the disk a boot disk. It gets loaded by the
BIOS at 0x7C00, reads the root directory into address
0x7E00, and looks at the first root directory entry. If
that file is called B.COM, it uses single sector reads to
load the file into address 0x10000 and then jumps to the
loaded file image.
EXAMPLE
Create a Plan 9 boot floppy on a previously formatted
diskette:
disk/format -f -b bb -d /dev/fd0disk /386/b.com
SOURCE
/sys/src/cmd/disk/prep.c
/sys/src/cmd/disk/format.c
/sys/src/boot/pc/bb.s
SEE ALSO
floppy(3), wren(3), b.com(8)
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