<s>
In	O
BSD-derived	O
computer	B-General_Concept
operating	I-General_Concept
systems	I-General_Concept
(	O
including	O
NetBSD	B-Device
,	O
OpenBSD	B-Operating_System
,	O
FreeBSD	B-Operating_System
and	O
DragonFly	B-Application
BSD	I-Application
)	O
and	O
in	O
related	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
SunOS	B-Operating_System
,	O
a	O
disklabel	B-Application
is	O
a	O
record	O
stored	O
on	O
a	O
data	B-General_Concept
storage	I-General_Concept
device	I-General_Concept
such	O
as	O
a	O
hard	B-Device
disk	I-Device
that	O
contains	O
information	O
about	O
the	O
location	O
of	O
the	O
partitions	B-Application
on	O
the	O
disk	O
.	O
</s>
<s>
Disklabels	B-Application
were	O
introduced	O
in	O
the	O
4.3BSD-Tahoe	O
release	O
.	O
</s>
<s>
Disklabels	B-Application
are	O
usually	O
edited	O
using	O
the	O
utility	O
.	O
</s>
<s>
In	O
later	O
versions	O
of	O
FreeBSD	B-Operating_System
,	O
this	O
was	O
renamed	O
as	O
.	O
</s>
<s>
In	O
historic	O
Bell	O
Labs	O
and	O
BSD	B-Operating_System
Unix	I-Operating_System
releases	O
,	O
disk	B-Application
partitioning	I-Application
was	O
fixed	O
,	O
compiled	O
into	O
each	O
device	O
driver	O
at	O
the	O
time	O
the	O
kernel	O
was	O
compiled	O
.	O
</s>
<s>
The	O
fixed	O
partitions	B-Application
overlapped	O
,	O
allowing	O
the	O
disk	O
to	O
be	O
used	O
with	O
different	O
layouts	O
by	O
careful	O
selection	O
of	O
a	O
non-overlapping	O
subset	O
of	O
the	O
partitions	B-Application
.	O
</s>
<s>
This	O
was	O
not	O
originally	O
viewed	O
as	O
a	O
problem	O
because	O
there	O
were	O
only	O
a	O
small	O
number	O
of	O
disk	B-General_Concept
drives	I-General_Concept
supported	O
by	O
each	O
driver	O
,	O
and	O
Unix	O
only	O
ran	O
on	O
one	O
vendor	O
's	O
hardware	O
.	O
</s>
<s>
The	O
introduction	O
of	O
standardized	O
disk	O
interfaces	O
—	O
SMD	B-Architecture
,	O
ESDI	B-Architecture
and	O
SCSI	B-Architecture
—	O
and	O
a	O
substantial	O
market	O
in	O
third-party	O
controllers	O
and	O
drives	O
resulted	O
in	O
significant	O
inconvenience	O
,	O
since	O
a	O
Unix	O
system	O
's	O
operators	O
would	O
have	O
to	O
recompile	O
the	O
kernel	O
in	O
order	O
to	O
add	O
an	O
appropriate	O
partition	B-Application
layout	O
for	O
every	O
different	O
disk	O
they	O
attached	O
to	O
a	O
system	O
.	O
</s>
<s>
For	O
the	O
4.3-Tahoe	O
release	O
,	O
which	O
supported	O
a	O
non-Digital	O
Equipment	O
Corporation	O
platform	O
,	O
the	O
CCI	O
Power	O
6/32	O
,	O
Berkeley	O
implemented	O
a	O
new	O
partitioning	B-Application
scheme	O
based	O
on	O
an	O
on-disk	O
data	O
structure	O
and	O
the	O
disklabel(8 )	O
command	O
.	O
</s>
<s>
(	O
Such	O
on-disk	O
partition	B-Application
maps	O
were	O
already	O
well-known	O
on	O
other	O
operating	B-General_Concept
systems	I-General_Concept
,	O
and	O
only	O
the	O
specific	O
format	O
,	O
not	O
the	O
fact	O
of	O
partition	B-Application
labels	O
generally	O
,	O
was	O
invented	O
by	O
Berkeley	O
.	O
)	O
</s>
<s>
Traditionally	O
,	O
the	O
disklabel	B-Application
was	O
embedded	O
in	O
the	O
first-stage	O
bootstrap	B-Operating_System
loader	I-Operating_System
,	O
in	O
the	O
first	O
sector	O
or	O
track	O
of	O
the	O
disk	O
,	O
where	O
the	O
computer	O
's	O
firmware	O
expected	O
a	O
boot	B-Application
loader	I-Application
to	O
be	O
.	O
</s>
<s>
Having	O
the	O
label	O
embedded	O
in	O
the	O
boot	B-Application
loader	I-Application
meant	O
that	O
the	O
loader	O
did	O
not	O
itself	O
need	O
to	O
contain	O
code	O
to	O
locate	O
and	O
read	O
the	O
label	O
from	O
the	O
disk	O
.	O
</s>
<s>
However	O
,	O
this	O
system	O
only	O
works	O
when	O
the	O
computer	O
firmware	O
simply	O
loads	O
and	O
executes	O
the	O
boot	B-Application
loader	I-Application
without	O
attempting	O
to	O
determine	O
whether	O
it	O
is	O
valid	O
.	O
</s>
<s>
In	O
the	O
world	O
of	O
IBM	O
PC	O
compatibles	O
,	O
disks	O
are	O
usually	O
partitioned	O
using	O
the	O
PC	B-Operating_System
BIOS	I-Operating_System
's	O
master	B-Device
boot	I-Device
record	I-Device
(	O
MBR	O
)	O
Partition	B-Application
Table	O
scheme	O
instead	O
,	O
and	O
the	O
BSD	B-Operating_System
partitioning	B-Application
scheme	O
is	O
nested	O
within	O
a	O
single	O
,	O
primary	O
,	O
MBR	O
partition	B-Application
(	O
just	O
as	O
the	O
"	O
extended	O
"	O
partitioning	B-Application
scheme	O
is	O
nested	O
within	O
a	O
single	O
primary	O
partition	B-Application
with	O
extended	B-Application
boot	I-Application
records	I-Application
)	O
.	O
</s>
<s>
Sometimes	O
(	O
particularly	O
in	O
FreeBSD	B-Operating_System
)	O
,	O
the	O
primary	O
MBR	O
partitions	B-Application
are	O
referred	O
to	O
as	O
slices	B-Application
and	O
the	O
subdivisions	O
of	O
a	O
primary	O
MBR	O
partition	B-Application
(	O
for	O
the	O
nested	O
BSD	B-Operating_System
partitioning	B-Application
scheme	O
)	O
that	O
are	O
described	O
by	O
its	O
disklabel	B-Application
are	O
called	O
partitions	B-Application
.	O
</s>
<s>
The	O
BSD	B-Application
disklabel	I-Application
is	O
contained	O
within	O
the	O
volume	B-Device
boot	I-Device
record	I-Device
of	O
its	O
primary	O
MBR	O
partition	B-Application
.	O
</s>
<s>
The	O
MBR	O
partition	B-Application
IDs	O
for	O
primary	O
partitions	B-Application
that	O
are	O
subdivided	O
using	O
BSD	B-Application
disklabels	I-Application
are	O
(	O
386BSD	O
and	O
FreeBSD	B-Operating_System
)	O
,	O
(	O
OpenBSD	B-Operating_System
)	O
,	O
(	O
NetBSD	B-Device
)	O
,	O
and	O
(	O
DragonFly	B-Application
BSD	I-Application
)	O
.	O
</s>
<s>
This	O
format	O
has	O
a	O
similar	O
goal	O
as	O
the	O
extended	B-Application
partitions	I-Application
and	O
logical	O
partition	B-Application
system	O
used	O
by	O
MS-DOS	O
,	O
Windows	O
and	O
Linux	O
.	O
</s>
<s>
The	O
same	O
PC	O
hard	B-Device
drive	I-Device
can	O
have	O
both	O
BSD	B-Application
disklabel	I-Application
partitions	B-Application
and	O
the	O
MS-DOS	O
type	O
logical	O
partitions	B-Application
in	O
separate	O
primary	O
partitions	B-Application
.	O
</s>
<s>
FreeBSD	B-Operating_System
and	O
other	O
BSD	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
can	O
access	O
both	O
the	O
BSD	B-Application
disklabel	I-Application
subdivided	O
partition	B-Application
and	O
the	O
MS-DOS	O
type	O
Extended/Logical	O
partitions	B-Application
.	O
</s>
<s>
BSD	B-Application
disklabels	I-Application
traditionally	O
contain	O
8	O
entries	O
for	O
describing	O
partitions	B-Application
.	O
</s>
<s>
Some	O
BSD	B-Operating_System
variants	O
have	O
since	O
increased	O
this	O
to	O
16	O
partitions	B-Application
,	O
labeled	O
'	O
a	O
 '	O
through	O
to	O
'	O
p	O
 '	O
.	O
</s>
<s>
Also	O
by	O
convention	O
,	O
partitions	B-Application
'	O
a	O
 '	O
,	O
'	O
b	O
 '	O
,	O
and	O
'	O
c	O
 '	O
have	O
fixed	O
meanings	O
:	O
</s>
<s>
Partition	B-Application
'	O
a	O
 '	O
is	O
the	O
"	O
root	O
"	O
partition	B-Application
,	O
the	O
volume	O
from	O
which	O
the	O
operating	B-General_Concept
system	I-General_Concept
is	O
bootstrapped	B-Operating_System
.	O
</s>
<s>
The	O
boot	B-Operating_System
code	O
in	O
the	O
Volume	B-Device
Boot	I-Device
Record	I-Device
containing	O
the	O
disklabel	B-Application
is	O
thus	O
simplified	O
,	O
as	O
it	O
need	O
only	O
look	O
in	O
one	O
fixed	O
location	O
to	O
find	O
the	O
location	O
of	O
the	O
boot	B-Operating_System
volume	O
;	O
</s>
<s>
Partition	B-Application
'	O
b	O
 '	O
is	O
the	O
"	O
swap	O
"	O
partition	B-Application
;	O
</s>
<s>
Partition	B-Application
'	O
c	O
 '	O
overlaps	O
all	O
of	O
the	O
other	O
partitions	B-Application
and	O
describes	O
the	O
entire	O
disk	O
.	O
</s>
<s>
On	O
systems	O
where	O
the	O
disklabel	B-Application
co-exists	O
with	O
another	O
partitioning	B-Application
scheme	O
(	O
such	O
as	O
on	O
PC	O
hardware	O
)	O
,	O
partition	B-Application
'	O
c	O
 '	O
may	O
actually	O
only	O
extend	O
to	O
an	O
area	O
of	O
disk	O
allocated	O
to	O
the	O
BSD	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
,	O
and	O
partition	B-Application
'	O
d	O
 '	O
is	O
used	O
to	O
cover	O
the	O
whole	O
physical	O
disk	O
.	O
</s>
