<s>
A	O
sparse	B-Operating_System
image	I-Operating_System
is	O
a	O
type	O
of	O
disk	B-Application
image	I-Application
file	O
used	O
on	O
macOS	B-Application
that	O
grows	O
in	O
size	O
as	O
the	O
user	O
adds	O
data	O
to	O
the	O
image	O
,	O
taking	O
up	O
only	O
as	O
much	O
disk	O
space	O
as	O
stored	O
in	O
it	O
.	O
</s>
<s>
Encrypted	O
sparse	B-Operating_System
image	I-Operating_System
files	O
are	O
used	O
to	O
secure	O
a	O
user	O
's	O
home	O
directory	O
by	O
the	O
FileVault	O
feature	O
in	O
Mac	B-Application
OS	I-Application
X	O
Snow	O
Leopard	B-Application
and	O
earlier	O
.	O
</s>
<s>
Sparse	B-Operating_System
images	I-Operating_System
can	O
be	O
created	O
using	O
Disk	B-Application
Utility	I-Application
.	O
</s>
<s>
Unlike	O
a	O
full	O
image	O
file	O
(	O
)	O
,	O
which	O
takes	O
up	O
as	O
much	O
actual	O
space	O
as	O
the	O
real	O
disk	O
it	O
represents	O
(	O
regardless	O
of	O
the	O
amount	O
of	O
unused	O
space	O
)	O
,	O
a	O
sparse	B-Operating_System
image	I-Operating_System
file	O
(	O
)	O
takes	O
up	O
only	O
as	O
much	O
actual	O
disk	O
space	O
as	O
the	O
data	O
contained	O
within	O
,	O
up	O
to	O
a	O
maximum	O
of	O
the	O
capacity	O
assigned	O
during	O
creation	O
.	O
</s>
<s>
A	O
customized	O
"	O
.sparseimage	B-Operating_System
"	O
image	O
file	O
can	O
be	O
assigned	O
a	O
larger	O
total	O
capacity	O
than	O
the	O
physical	O
volume	O
(	O
or	O
HD	O
partition	O
)	O
on	O
which	O
it	O
originally	O
resides	O
.	O
</s>
<s>
As	O
noted	O
above	O
,	O
while	O
mounted	O
image	O
files	O
automatically	O
expand	O
to	O
their	O
preassigned	O
limit	O
when	O
data	O
is	O
added	O
,	O
they	O
cannot	O
be	O
arbitrarily	O
resized	O
without	O
the	O
use	O
of	O
Disk	B-Application
Utility	I-Application
,	O
,	O
or	O
other	O
such	O
software	O
.	O
</s>
<s>
Mac	B-Application
OS	I-Application
X	I-Application
Leopard	I-Application
introduced	O
the	O
concept	O
of	O
the	O
sparse	O
bundle	B-Application
.	O
</s>
<s>
Instead	O
of	O
a	O
single	O
big	O
file	O
,	O
a	O
sparse	O
bundle	B-Application
is	O
a	O
bundle	B-Application
(	O
directory	O
)	O
containing	O
a	O
number	O
of	O
files	O
called	O
bands	O
,	O
each	O
on	O
the	O
order	O
of	O
8	O
MB	O
in	O
size	O
.	O
</s>
<s>
This	O
means	O
even	O
though	O
to	O
the	O
end	O
user	O
the	O
sparse	O
bundle	B-Application
appears	O
as	O
a	O
single	O
file	O
,	O
it	O
is	O
composed	O
of	O
smaller	O
files	O
.	O
</s>
<s>
As	O
of	O
Mac	B-Application
OS	I-Application
X	O
10.8	O
,	O
the	O
bands	O
are	O
8	O
MiB	O
(	O
)	O
each	O
.	O
</s>
<s>
This	O
allows	O
easier	O
shrinking	O
of	O
the	O
amount	O
of	O
space	O
used	O
on	O
the	O
underlying	O
filesystem	B-Application
when	O
the	O
a	O
large	O
amount	O
of	O
data	O
is	O
deleted	O
inside	O
the	O
disk	B-Application
image	I-Application
,	O
as	O
long	O
as	O
the	O
code	O
supporting	O
the	O
filesystem	B-Application
inside	O
the	O
image	O
notifies	O
the	O
kernel	O
of	O
the	O
"	O
releasing	O
"	O
of	O
blocks	O
,	O
as	O
happens	O
in	O
filesystems	B-Application
that	O
support	O
SSD	O
"	O
trim	O
"	O
operations	O
to	O
be	O
triggered	O
automatically	O
for	O
de-allocated	O
filesystem	B-Application
blocks	O
.	O
</s>
<s>
Sparse	O
bundle	B-Application
advantages	O
over	O
non-diskimage	O
backup	O
for	O
Time	B-Operating_System
Machine	I-Operating_System
:	O
</s>
<s>
the	O
entire	O
sparse	O
bundle	B-Application
is	O
replicable	O
from	O
one	O
location	O
to	O
another	O
;	O
this	O
is	O
particularly	O
useful	O
when	O
upgrading	O
the	O
backup	O
storage	O
and	O
when	O
the	O
on-site	O
backup	O
storage	O
needs	O
to	O
be	O
replicated	O
to	O
an	O
off-site	O
backup	O
storage	O
.	O
</s>
<s>
A	O
tool	O
such	O
as	O
rsync	B-Application
may	O
be	O
used	O
to	O
keep	O
one	O
or	O
more	O
disk	B-Application
images	I-Application
consistent	O
across	O
various	O
systems	O
.	O
</s>
