part - partition table editor
part [device] ...
Part is a screen oriented partition table editor.
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'.
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.
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.
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. Use this key!
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. /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.
With arguments, part will use the given devices or files. Without
arguments, part will use all interesting block devices in /dev sorted by
device number and starting with /dev/hd0.
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.
The name of the device is highlighted when it has not been read yet.
Head or sector numbers are highlighted if the partition does not start or
end at a cylinder boundary.
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.
Part complies with the good old UNIX tradition of trusting the user. It
will write any table, no matter how bad. You have been warned.
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.)
Extended partitions are a mess that is only made slightly better by part
by translating the base offsets to absolute numbers. It is better to use
DOS fdisk to create them, but if you insist on using part then this is
what they should look like:
The extended partition entry in the primary partition table must
cover the whole logical partition space within it.
The area thus created is split in segments, each segment contains a
partition table in sector 0 and one (just one) logical partition.
The first entry of a segment's partition table describes this
logical partition: it's partition ID, base and size.
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
mkfs(1), fd(4), hd(4).
You can have a table read, messed up, and written in no time, be careful.
You can't type head or sector numbers directly.
Sectors are counted from 0 for consistency, but the partition table
counts from 1 like DOS addresses them. Most confusing.
You can't write a backup copy to a file, that's what dd(1) with count=1
Kees J. Bot (email@example.com)