<s>
An	O
extended	B-Application
boot	I-Application
record	I-Application
(	O
EBR	O
)	O
,	O
or	O
extended	B-Application
partition	I-Application
boot	I-Application
record	I-Application
(	O
EPBR	B-Application
)	O
,	O
is	O
a	O
descriptor	O
for	O
a	O
logical	O
partition	B-Application
under	O
the	O
common	O
DOS	O
disk	O
drive	O
partitioning	B-Application
system	O
.	O
</s>
<s>
In	O
that	O
system	O
,	O
when	O
one	O
(	O
and	O
only	O
one	O
)	O
partition	B-Application
record	O
entry	O
in	O
the	O
master	B-Device
boot	I-Device
record	I-Device
(	O
MBR	B-Device
)	O
is	O
designated	O
an	O
extended	B-Application
partition	I-Application
,	O
then	O
that	O
partition	B-Application
can	O
be	O
subdivided	O
into	O
a	O
number	O
of	O
logical	O
partitions	B-Application
.	O
</s>
<s>
The	O
actual	O
structure	O
of	O
that	O
extended	B-Application
partition	I-Application
is	O
described	O
by	O
one	O
or	O
more	O
EBRs	O
,	O
which	O
are	O
located	O
inside	O
the	O
extended	B-Application
partition	I-Application
.	O
</s>
<s>
The	O
first	O
(	O
and	O
sometimes	O
only	O
)	O
EBR	O
will	O
always	O
be	O
located	O
on	O
the	O
very	O
first	O
sector	O
of	O
the	O
extended	B-Application
partition	I-Application
.	O
</s>
<s>
Unlike	O
primary	O
partitions	B-Application
,	O
which	O
are	O
all	O
described	O
by	O
a	O
single	O
partition	B-Application
table	O
within	O
the	O
MBR	B-Device
,	O
and	O
thus	O
limited	O
in	O
number	O
,	O
each	O
EBR	O
precedes	O
the	O
logical	O
partition	B-Application
it	O
describes	O
.	O
</s>
<s>
If	O
another	O
logical	O
partition	B-Application
follows	O
,	O
then	O
the	O
first	O
EBR	O
will	O
contain	O
an	O
entry	O
pointing	O
to	O
the	O
next	O
EBR	O
;	O
thus	O
,	O
multiple	O
EBRs	O
form	O
a	O
linked	B-Data_Structure
list	I-Data_Structure
.	O
</s>
<s>
This	O
means	O
the	O
number	O
of	O
logical	B-Application
drives	I-Application
that	O
can	O
be	O
formed	O
within	O
an	O
extended	B-Application
partition	I-Application
is	O
limited	O
only	O
by	O
the	O
amount	O
of	O
available	O
disk	O
space	O
in	O
the	O
given	O
extended	B-Application
partition	I-Application
.	O
</s>
<s>
While	O
in	O
Windows	B-Application
versions	O
up	O
to	O
XP	B-Application
logical	O
partitions	B-Application
within	O
the	O
extended	B-Application
partition	I-Application
were	O
aligned	O
following	O
conventions	O
called	O
"	B-Device
drive	I-Device
geometry	I-Device
"	I-Device
or	I-Device
"	I-Device
CHS	I-Device
"	I-Device
,	O
since	O
Windows	B-Application
Vista	I-Application
they	O
are	O
aligned	O
to	O
a	O
1-MiB	O
boundary	O
.	O
</s>
<s>
Due	O
to	O
this	O
difference	O
in	O
alignment	O
,	O
the	O
Logical	O
Disk	O
Manager	O
of	O
XP	B-Application
(	O
Disk	O
Management	O
)	O
may	O
delete	O
these	O
extended	B-Application
partitions	I-Application
without	O
warning	O
.	O
</s>
<s>
EBRs	O
have	O
essentially	O
the	O
same	O
structure	O
as	O
the	O
MBR	B-Device
;	O
except	O
only	O
the	O
first	O
two	O
entries	O
of	O
the	O
partition	B-Application
table	O
are	O
supposed	O
to	O
be	O
used	O
,	O
besides	O
having	O
the	O
mandatory	O
boot	B-Device
record	I-Device
signature	O
(	O
or	O
magic	O
number	O
)	O
of	O
at	O
the	O
end	O
of	O
the	O
sector	O
.	O
</s>
<s>
This	O
2-byte	O
signature	O
appears	O
in	O
a	O
disk	B-Application
editor	I-Application
as	O
first	O
and	O
last	O
,	O
because	O
IBM-compatible	O
PCs	O
store	O
hexadecimal	O
words	O
in	O
little-endian	O
order	O
(	O
see	O
table	O
below	O
)	O
.	O
</s>
<s>
+	O
Common	O
Structure	O
of	O
Extended	B-Application
Boot	I-Application
Records	I-Application
:	O
Offsets	O
within	O
EBR	O
sectors	O
Contents	O
Size	O
Hex	O
Dec	B-Application
bytes	B-Application
Generally	O
unused	O
;	O
normally	O
filled	O
with	O
zeroes	O
;	O
may	O
contain	O
another	O
boot	O
loader	O
i.e.	O
</s>
<s>
a	O
partition	B-Device
boot	I-Device
record	I-Device
,	O
for	O
example	O
in	O
conjunction	O
with	O
Advanced	O
Active	O
Partitions	B-Application
446	O
1BE	O
–	O
1CD	O
446	O
–	O
461	O
Partition	B-Application
table	O
's	O
first	O
entry	O
16	O
1CE	O
–	O
1DD	O
462	O
–	O
477	O
Partition	B-Application
table	O
's	O
second	O
entry	O
16	O
1DE	O
–	O
1ED	O
478	O
–	O
493	O
Unused	O
third	O
entry	O
filled	O
with	O
zeroes	O
16	O
1EE	O
–	O
1FD	O
494	O
–	O
509	O
Unused	O
fourth	O
entry	O
filled	O
with	O
zeroes	O
16	O
1FE	O
-	O
1FF	O
510	O
-	O
511	O
Signature	O
in	O
big-endian	O
network	O
order	O
,	O
same	O
as	O
little-endian	O
.	O
</s>
<s>
The	O
IBM	O
Boot	O
Manager	O
(	O
included	O
with	O
OS/2	B-Application
operating	B-General_Concept
systems	I-General_Concept
and	O
some	O
early	O
versions	O
of	O
Partition	B-Application
Magic	I-Application
)	O
,	O
adds	O
at	O
least	O
one	O
9-byte	O
entry	O
(	O
starting	O
at	O
offset	O
)	O
to	O
each	O
EBR	O
sector	O
.	O
</s>
<s>
The	O
entry	O
consists	O
of	O
a	O
flag	O
value	O
byte	B-Application
(	O
indicating	O
if	O
the	O
partition	B-Application
is	O
on	O
the	O
IBM	O
Boot	O
Manager	O
menu	O
)	O
followed	O
by	O
an	O
8-byte	O
ASCII	O
string	O
which	O
is	O
the	O
name	O
to	O
be	O
used	O
on	O
the	O
menu	O
.	O
</s>
<s>
If	O
the	O
partition	B-Application
is	O
not	O
included	O
on	O
the	O
boot	O
menu	O
(	O
such	O
as	O
data	O
only	O
partitions	B-Application
)	O
,	O
the	O
flag	O
byte	B-Application
is	O
zero	O
;	O
in	O
which	O
case	O
,	O
the	O
following	O
8-byte	O
field	O
may	O
contain	O
an	O
ASCII	O
representation	O
of	O
that	O
partition	B-Application
's	O
starting	O
sector	O
number	O
(	O
in	O
hexadecimal	O
)	O
.	O
</s>
<s>
+	O
Structure	O
of	O
an	O
MBR	B-Device
or	O
EBR	O
16-byte	O
Partition	B-Application
Table	O
Entry	O
:	O
Offsets	O
within	O
entry	O
Bytes	B-Application
Description	O
Hex	O
Dec	B-Application
1	O
?	O
E1	O
0	O
1	O
Boot	O
indicator	O
(	O
80h	O
for	O
active	O
;	O
otherwise	O
,	O
00h	O
)	O
1	O
?	O
F	O
-	O
1	O
?	O
1	O
1	O
–	O
3	O
3	O
CHS	B-Device
cylinder-head-sector	B-Device
address	O
:	O
partition	B-Application
start	O
1	O
?	O
2	O
4	O
1	O
Partition	B-Application
type	I-Application
code	O
1	O
?	O
3	O
-	O
1	O
?	O
5	O
5	O
–	O
7	O
3	O
CHS	B-Device
cylinder-head-sector	B-Device
address	O
:	O
partition	B-Application
end	O
1	O
?	O
6	O
-	O
1	O
?	O
9	O
8	O
–	O
11	O
4	O
LBA	B-Device
logical	B-Device
block	I-Device
address	I-Device
:	O
partition	B-Application
start	O
1	O
?	O
A	O
-	O
1	O
?	O
D	O
12	O
–	O
15	O
4	O
Partition	B-Application
size	O
(	O
in	O
sectors	O
)	O
1	O
:	O
For	O
1	O
?	O
E	O
read	O
1BE	O
or	O
1CE	O
to	O
get	O
the	O
hex	O
.	O
</s>
<s>
The	O
partition	B-Application
type	I-Application
of	O
an	O
extended	B-Application
partition	I-Application
is	O
(	O
addressing	O
)	O
or	O
(	O
LBA	B-Device
addressing	O
)	O
.	O
</s>
<s>
DR	B-Application
DOS	I-Application
6.0	O
and	O
higher	O
support	O
secured	O
extended	B-Application
partitions	I-Application
using	O
,	O
which	O
are	O
invisible	O
to	O
other	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Since	O
non-LBA-enabled	O
versions	O
of	O
DR-DOS	B-Application
up	O
to	O
including	O
7.03	O
do	O
not	O
recognize	O
the	O
partition	B-Application
type	I-Application
and	O
other	O
operating	B-General_Concept
systems	I-General_Concept
do	O
not	O
recognize	O
the	O
type	O
,	O
this	O
can	O
also	O
be	O
utilized	O
to	O
occupy	O
space	O
up	O
to	O
the	O
first	O
8	O
GB	O
of	O
the	O
disk	O
for	O
use	O
under	O
DR-DOS	B-Application
(	O
for	O
logical	B-Application
drives	I-Application
in	O
secured	O
or	O
non-secured	O
partitions	B-Application
)	O
,	O
and	O
still	O
use	O
to	O
allocate	O
the	O
remainder	O
of	O
the	O
disk	O
for	O
LBA-enabled	O
operating	B-General_Concept
systems	I-General_Concept
in	O
a	O
non-conflictive	O
fashion	O
.	O
</s>
<s>
Similarly	O
,	O
Linux	B-Application
supports	O
the	O
concept	O
of	O
a	O
second	O
extended	B-Application
partition	I-Application
chain	O
with	O
type	O
this	O
type	O
is	O
hidden	O
(	O
unknown	O
)	O
for	O
other	O
operating	B-General_Concept
systems	I-General_Concept
supporting	O
only	O
one	O
chain	O
.	O
</s>
<s>
Other	O
extended	B-Application
partition	I-Application
types	O
which	O
may	O
hold	O
EBRs	O
include	O
the	O
deliberately	O
hidden	O
types	O
,	O
,	O
and	O
,	O
the	O
access-restricted	O
types	O
and	O
,	O
and	O
the	O
secured	O
types	O
and	O
.	O
</s>
<s>
However	O
,	O
these	O
should	O
be	O
treated	O
private	O
to	O
the	O
operating	B-General_Concept
systems	I-General_Concept
and	O
tools	O
supporting	O
them	O
and	O
should	O
not	O
be	O
mounted	O
otherwise	O
.	O
</s>
<s>
The	O
CHS	B-Device
addresses	O
of	O
a	O
partition	B-Application
are	O
hard	O
to	O
interpret	O
without	O
knowledge	O
of	O
the	O
(	O
virtual	O
)	O
disk	O
geometry	O
,	O
because	O
CHS	B-Device
to	O
LBA	B-Device
translations	O
are	O
based	O
on	O
the	O
number	O
of	O
heads	O
and	O
the	O
number	O
of	O
sectors	O
per	O
track	O
.	O
</s>
<s>
However	O
,	O
the	O
given	O
LBA	B-Device
start	O
address	O
and	O
the	O
given	O
partition	B-Application
size	O
in	O
sectors	O
permit	O
to	O
calculate	O
a	O
disk	O
geometry	O
matching	O
the	O
given	O
CHS	B-Device
addresses	O
where	O
that	O
is	O
at	O
all	O
possible	O
.	O
</s>
<s>
CHS	B-Device
addressing	O
with	O
24	O
bits	O
always	O
uses	O
6	O
bits	O
for	O
up	O
to	O
63	O
sectors	O
per	O
track	O
(	O
1	O
...	O
63	O
)	O
,	O
and	O
INT	B-Device
13h	I-Device
disk	O
access	O
generally	O
uses	O
8	O
bits	O
for	O
up	O
to	O
256	O
heads	O
(	O
0	O
...	O
255	O
)	O
,	O
leaving	O
10	O
bits	O
for	O
up	O
to	O
1024	O
cylinders	O
(	O
0	O
...	O
1023	O
)	O
.	O
</s>
<s>
ATA	B-Protocol
CHS	B-Device
addresses	O
always	O
use	O
4	O
bits	O
for	O
up	O
to	O
16	O
heads	O
(	O
0	O
...	O
15	O
)	O
,	O
this	O
leaves	O
14	O
bits	O
for	O
up	O
to	O
16,383	O
cylinders	O
(	O
)	O
in	O
ATA-5	B-Protocol
24	O
bits	O
CHS	B-Device
address	O
translations	O
.	O
</s>
<s>
The	O
following	O
are	O
general	O
rules	O
that	O
apply	O
only	O
to	O
values	O
found	O
in	O
the	O
4-byte	O
fields	O
of	O
an	O
EBR	O
's	O
partition	B-Application
table	O
entries	O
(	O
cf	O
.	O
</s>
<s>
These	O
values	O
depend	O
upon	O
the	O
partitioning	B-Application
tool(s )	O
used	O
to	O
create	O
or	O
alter	O
them	O
,	O
and	O
in	O
fact	O
,	O
most	O
operating	B-General_Concept
systems	I-General_Concept
that	O
use	O
the	O
extended	O
partitioning	B-Application
scheme	O
(	O
including	O
Microsoft	O
MS-DOS	O
and	O
Windows	B-Application
,	O
and	O
Linux	B-Application
)	O
ignore	O
the	O
"	O
partition	B-Application
size	O
"	O
value	O
in	O
entries	O
which	O
point	O
to	O
another	O
EBR	O
sector	O
.	O
</s>
<s>
One	O
exception	O
is	O
that	O
value	O
must	O
be	O
one	O
or	O
greater	O
for	O
Linux	B-Application
operating	I-Application
systems	I-Application
.	O
</s>
<s>
The	O
first	O
entry	O
of	O
an	O
EBR	O
partition	B-Application
table	O
points	O
to	O
the	O
logical	O
partition	B-Application
belonging	O
to	O
that	O
EBR	O
:	O
</s>
<s>
Note	O
:	O
This	O
is	O
often	O
the	O
same	O
value	O
for	O
each	O
EBR	O
on	O
the	O
same	O
hard	O
disk	O
;	O
usually	O
63	O
for	O
Windows	B-Application
XP	I-Application
or	O
older	O
.	O
</s>
<s>
Note	O
:	O
Any	O
unused	O
sectors	O
between	O
EBR	O
and	O
logical	B-Application
drive	I-Application
are	O
not	O
considered	O
part	O
of	O
the	O
logical	B-Application
drive	I-Application
.	O
</s>
<s>
The	O
second	O
entry	O
of	O
an	O
EBR	O
partition	B-Application
table	O
will	O
contain	O
zero-bytes	O
if	O
it	O
's	O
the	O
last	O
EBR	O
in	O
the	O
extended	B-Application
partition	I-Application
;	O
otherwise	O
,	O
it	O
points	O
to	O
the	O
next	O
EBR	O
in	O
the	O
EBR	O
chain	O
.	O
</s>
<s>
Partition	B-Application
type	I-Application
code	O
=	O
(	O
addressing	O
)	O
or	O
(	O
LBA	B-Device
addressing	O
)	O
.	O
</s>
<s>
in	O
other	O
words	O
,	O
the	O
EBR	O
must	O
have	O
a	O
valid	O
partition	B-Application
type	I-Application
,	O
just	O
as	O
a	O
partition	B-Application
must	O
have	O
a	O
valid	O
partition	B-Application
type	I-Application
.	O
</s>
<s>
Note	O
:	O
Unlike	O
the	O
first	O
entry	O
in	O
an	O
EBR	O
's	O
partition	B-Application
table	O
,	O
this	O
number	O
of	O
sectors	O
count	O
includes	O
the	O
next	O
logical	O
partition	B-Application
's	O
EBR	O
sector	O
along	O
with	O
the	O
other	O
sectors	O
in	O
its	O
otherwise	O
unused	O
track	O
.	O
</s>
<s>
The	O
diagrams	O
above	O
are	O
not	O
to	O
scale	O
:	O
The	O
thin	O
white	O
lines	O
between	O
each	O
"	O
EBR	O
"	O
and	O
its	O
logical	O
"	O
partition	B-Application
"	O
represent	O
the	O
remainder	O
of	O
an	O
unused	O
area	O
usually	O
63	O
sectors	O
in	O
length	O
;	O
including	O
the	O
single	O
EBR	O
sector	O
(	O
shown	O
at	O
a	O
greatly	O
exaggerated	O
size	O
)	O
.	O
</s>
<s>
On	O
some	O
systems	O
,	O
a	O
large	O
gap	O
of	O
unused	O
space	O
may	O
exist	O
between	O
the	O
end	O
of	O
a	O
logical	O
partition	B-Application
and	O
the	O
next	O
EBR	O
,	O
or	O
between	O
the	O
last	O
logical	O
partition	B-Application
and	O
the	O
end	O
of	O
the	O
whole	O
extended	B-Application
partition	I-Application
itself	O
,	O
if	O
any	O
previously	O
created	O
logical	O
partition	B-Application
has	O
been	O
deleted	O
or	O
resized	O
(	O
shrunk	O
)	O
.	O
</s>
<s>
The	O
interleaving	O
of	O
EBRs	O
and	O
partitions	B-Application
shown	O
above	O
is	O
typical	O
but	O
not	O
required	O
.	O
</s>
<s>
It	O
is	O
legitimate	O
to	O
have	O
two	O
or	O
more	O
consecutive	O
EBRs	O
followed	O
by	O
two	O
or	O
more	O
regions	O
of	O
partition	B-Application
data	O
.	O
</s>
<s>
Linux	B-Application
and	O
similar	O
operating	B-General_Concept
systems	I-General_Concept
designate	O
IDE	O
hard	O
disks	O
as	O
/dev/hda	O
for	O
the	O
first	O
hard	O
disk	O
,	O
/dev/hdb	O
for	O
the	O
second	O
hard	O
disk	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
Likewise	O
SCSI	B-Architecture
and	O
in	O
later	O
kernels	O
also	O
IDE	O
and	O
SATA	O
hard	O
disks	O
are	O
identified	O
as	O
/dev/sda	O
for	O
the	O
first	O
disk	O
,	O
etc	O
.	O
</s>
<s>
The	O
up	O
to	O
four	O
partitions	B-Application
defined	O
in	O
the	O
master	B-Device
boot	I-Device
record	I-Device
are	O
designated	O
as	O
/dev/hda1	O
...	O
/dev/hda4	O
for	O
/dev/hda	O
.	O
</s>
<s>
The	O
fifth	O
partition	B-Application
in	O
this	O
scheme	O
,	O
e.g.	O
,	O
/dev/hda5	O
,	O
corresponds	O
to	O
the	O
first	O
logical	B-Application
drive	I-Application
.	O
</s>
<s>
The	O
sixth	O
partition	B-Application
/dev/hda6	O
would	O
then	O
correspond	O
to	O
the	O
second	O
logical	B-Application
drive	I-Application
,	O
or	O
in	O
other	O
words	O
,	O
the	O
extended	B-Application
partition	I-Application
containers	O
are	O
not	O
counted	O
.	O
</s>
<s>
Only	O
the	O
outermost	O
extended	B-Application
partition	I-Application
defined	O
in	O
the	O
MBR	B-Device
(	O
one	O
of	O
/dev/hda1	O
...	O
/dev/hda4	O
)	O
has	O
a	O
name	O
in	O
this	O
scheme	O
.	O
</s>
<s>
This	O
shows	O
an	O
extended	B-Application
partition	I-Application
with	O
6,000	O
sectors	O
and	O
3	O
logical	O
partitions	B-Application
.	O
</s>
<s>
Remark	O
:	O
Neither	O
a	O
tiny	O
extended	B-Application
partition	I-Application
with	O
only	O
3	O
MB	O
nor	O
a	O
hard	O
drive	O
with	O
20	O
sectors	O
per	O
track	O
are	O
realistic	O
but	O
these	O
values	O
have	O
been	O
chosen	O
to	O
make	O
this	O
example	O
more	O
readable	O
.	O
</s>
<s>
The	O
following	O
output	O
of	O
a	O
command	O
line	O
tool	O
shows	O
the	O
layout	O
of	O
a	O
disk	O
with	O
two	O
logical	B-Application
drives	I-Application
.	O
</s>
<s>
Details	O
for	O
the	O
FAT	B-Application
and	O
NTFS	B-Application
partitions	B-Application
stripped	O
,	O
the	O
line	O
annotated	O
with	O
Linux	B-Application
is	O
/dev/hda6	O
with	O
an	O
extended	B-Application
file	I-Application
system	I-Application
.	O
</s>
<s>
The	O
begin	O
of	O
/dev/hda5	O
shows	O
that	O
the	O
involved	O
operating	B-General_Concept
systems	I-General_Concept
PC	O
DOS	O
7	O
,	O
Windows	B-Application
NT	O
,	O
and	O
Debian	O
do	O
not	O
insist	O
on	O
any	O
extended	B-Application
partition	I-Application
alignment	O
with	O
a	O
gap	O
:	O
</s>
<s>
For	O
another	O
example	O
see	O
the	O
"	O
Linux	B-Application
Partition	B-Application
HOWTO	O
"	O
.	O
</s>
