part.8

操作系统设计与实现源码

.TH PART 8
.SH NAME
part \- partition table editor
.SH SYNOPSIS
.B part
.RI [ device "] ..."
.SH DESCRIPTION
.B Part
is a screen oriented partition table editor.
.PP
While editing you will see six lines of numbers, the first line shows the
device name and its geometry (number of cylinders, heads and sectors), the
second shows the start and end of the drive or partition you are working on,
the last four lines show the different partitions or subpartitions.  All
numbers except those on the second line can be edited.  Question marks are
showed instead of numbers if the partition table is not loaded yet.  You
have to select a device and type 'r'.
.PP
Editing is a simple matter of moving around with the arrow keys and changing
the values with + and \- (or PgUp and PgDn), or by typing the desired value.
The '?' key will give a small list of commands, the '!' key gives advice on
how to make a new entry.
.PP
The spacebar toggles between showing the size of the partition and the last
sector on the partition.  Useful to check if a partition is adjacent to the
next.
.PP
The 'm' key is "magical", it lets you cycle through a set of interesting
values for the base or size of a partition.  These values are: Aligned to a
cylinder, taped to other partitions (inside or outside), or filling out holes.
.BR "Use this key" !
.PP
Minix subpartition tables or extended partitions may be edited after hitting
the '>' key.  The number of this partition will be shown after the device
name on the second row, e.g.
.BR /dev/hd0:2 .
Minix subpartition tables are shown as is, but extended partition bases are
translated to absolute offsets on the screen to hide the gory details of their
implementation from the innocent user.  (Hit 'p' if you dare.)  The '<' key
will bring you back to the enclosing partition table.
.PP
With arguments,
.B part
will use the given devices or files.  Without arguments,
.B part
will use all interesting block devices in
.B /dev
sorted by device number and starting with
.BR /dev/hd0 .
.PP
Values that are out of range, overlapping, or otherwise strange are shown in
reverse video.  Values that may possibly be a problem for operating systems
other then Minix are shown in bold characters.
.PP
The name of the device is highlighted when it has not been read yet.
.PP
Head or sector numbers are highlighted if the partition does not start or
end at a cylinder boundary.
.PP
The base and/or size field is highlighted if they fall outside the device,
if they are inside some other partition, if the base equals the device's base
(no room for the boot sector), or if the size is zero.
.PP
.B Part
complies with the good old \s-2UNIX\s+2 tradition of trusting the user.
It will write any table, no matter how bad.  You have been warned.
.PP
By the way, as far as Minix is concerned there is absolutely no reason to
make partitions start precisely on a cylinder or track nor does it have to
be an exact number of cylinders long.  Minix only looks at the base and size
of a partition, the geometry of the drive doesn't have to be correct.  Other
Operating systems can be very picky about partitions that are not aligned.
Some partition editors may refuse to edit a table, others may even make a
mess of the table.  The only exception is the first partition, it
traditionally starts on the first track, not the first cylinder.  All
editors must understand this.  (Subpartition tables are Minix specific, so
there is no reason at all for any alignment.)
.SS "Extended Partitions"
Extended partitions are a mess that is only made slightly better by
.B part
by translating the base offsets to absolute numbers.  It is better to use DOS
.B fdisk
to create them, but if you insist on using
.B part
then this is what they should look like:
.RS
.sp
The extended partition entry in the primary partition table must cover the
whole logical partition space within it.
.sp
The area thus created is split in segments, each segment contains a partition
table in sector 0 and one (just one) logical partition.
.sp
The first entry of a segment's partition table describes this logical
partition: it's partition ID, base and size.
.sp
The second entry is an extended partition that describes base and size of
the next segment (partition table and logical partition).  The last segment's
partition table is empty, or contains one logical partition.
.SH "SEE ALSO"
.BR fd (4),
.BR hd (4).
.SH BUGS
You can have a table read, messed up, and written in no time, be careful.
.PP
You can't type head or sector numbers directly.
.PP
Sectors are counted from 0 for consistency, but the partition table counts
from 1 like DOS addresses them.  Most confusing.
.PP
You can't write a backup copy to a file, that's what
.BR dd (1)
with count=1 is for.
.SH AUTHOR
Kees J. Bot ([e-mail])