<s>
Time	B-Operating_System
Machine	I-Operating_System
is	O
the	O
backup	B-Application
mechanism	O
of	O
macOS	B-Application
,	O
the	O
desktop	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
developed	O
by	O
Apple	O
.	O
</s>
<s>
The	O
software	O
is	O
designed	O
to	O
work	O
with	O
both	O
local	O
storage	O
devices	O
and	O
network-attached	O
disks	O
,	O
and	O
is	O
most	O
commonly	O
used	O
with	O
external	O
disk	O
drives	O
connected	O
using	O
either	O
USB	B-Protocol
or	O
Thunderbolt	B-Protocol
.	O
</s>
<s>
It	O
was	O
first	O
introduced	O
in	O
Mac	B-Application
OS	I-Application
X	I-Application
10.5	I-Application
Leopard	I-Application
,	O
which	O
appeared	O
in	O
October	O
2007	O
and	O
incrementally	O
refined	O
in	O
subsequent	O
releases	O
of	O
macOS	B-Application
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
was	O
revamped	O
in	O
macOS	B-Operating_System
11	I-Operating_System
Big	I-Operating_System
Sur	I-Operating_System
to	O
support	O
APFS	B-Application
,	O
thereby	O
enabling	O
"	O
faster	O
,	O
more	O
compact	O
,	O
and	O
more	O
reliable	O
backups	B-Application
"	O
than	O
were	O
possible	O
previously	O
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
creates	O
incremental	O
backups	B-Application
of	O
files	O
that	O
can	O
be	O
restored	O
at	O
a	O
later	O
date	O
.	O
</s>
<s>
It	O
also	O
works	O
within	O
a	O
number	O
of	O
applications	O
such	O
as	O
Mail	B-Operating_System
and	O
iWork	B-Application
,	O
making	O
it	O
possible	O
to	O
restore	O
individual	O
objects	O
(	O
e.g.	O
</s>
<s>
“	O
Time	B-Operating_System
Machine	I-Operating_System
is	O
a	O
backup	B-Application
utility	O
,	O
not	O
an	O
archival	O
utility	O
,	O
it	O
is	O
not	O
intended	O
as	O
offline	O
storage	O
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
captures	O
the	O
most	O
recent	O
state	O
of	O
your	O
data	O
on	O
your	O
disk	O
.	O
</s>
<s>
For	O
backups	B-Application
to	O
a	O
network	O
drive	O
,	O
Time	B-Operating_System
Machine	I-Operating_System
allows	O
the	O
user	O
to	O
back	O
up	O
Mac	O
computers	O
over	O
the	O
network	O
,	O
and	O
supports	O
backing	O
up	O
to	O
certain	O
network	B-Application
attached	I-Application
storage	I-Application
devices	O
or	O
servers	O
,	O
depending	O
on	O
the	O
version	O
of	O
Time	B-Operating_System
Machine	I-Operating_System
.	O
</s>
<s>
Earlier	O
versions	O
worked	O
with	O
a	O
wide	O
variety	O
of	O
NAS	B-Application
servers	O
,	O
but	O
later	O
versions	O
require	O
the	O
server	O
to	O
support	O
a	O
recent	O
version	O
of	O
Apple	O
's	O
Apple	B-Protocol
Filing	I-Protocol
Protocol	I-Protocol
(	O
AFP	O
)	O
or	O
a	O
recent	O
version	O
of	O
the	O
Server	B-Operating_System
Message	I-Operating_System
Block	I-Operating_System
(	O
SMB	O
)	O
protocol	O
,	O
and	O
Time	B-Operating_System
Machine	I-Operating_System
no	O
longer	O
works	O
with	O
servers	O
using	O
earlier	O
versions	O
of	O
SMB	O
.	O
</s>
<s>
Some	O
of	O
the	O
legacy	O
support	O
can	O
be	O
re-enabled	O
by	O
using	O
hand-tuned	O
configuration	O
options	O
,	O
accessed	O
through	O
the	O
Terminal	B-Application
.	O
</s>
<s>
Apple	O
's	O
Time	B-Device
Capsule	I-Device
,	O
which	O
was	O
introduced	O
in	O
2008	O
and	O
discontinued	O
in	O
2018	O
,	O
acted	O
as	O
a	O
network	B-Application
storage	I-Application
device	O
specifically	O
for	O
Time	B-Operating_System
Machine	I-Operating_System
backups	B-Application
,	O
allowing	O
both	O
wired	O
and	O
wireless	O
backups	B-Application
to	O
the	O
Time	B-Device
Capsule	I-Device
's	O
internal	O
hard	O
drive	O
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
may	O
also	O
be	O
used	O
with	O
other	O
external	O
or	O
internal	O
volumes	O
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
saves	O
hourly	O
backups	B-Application
for	O
the	O
past	O
24	O
hours	O
,	O
daily	O
backups	B-Application
for	O
the	O
past	O
month	O
,	O
and	O
weekly	O
backups	B-Application
for	O
everything	O
older	O
than	O
a	O
month	O
until	O
the	O
volume	O
runs	O
out	O
of	O
space	O
.	O
</s>
<s>
At	O
that	O
point	O
,	O
Time	B-Operating_System
Machine	I-Operating_System
deletes	O
the	O
oldest	O
weekly	O
backup	B-Application
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
was	O
overhauled	O
in	O
macOS	B-Operating_System
11	I-Operating_System
Big	I-Operating_System
Sur	I-Operating_System
to	O
utilize	O
APFS	B-Application
,	O
Apple	O
's	O
modern	O
file	B-Application
system	I-Application
first	O
introduced	O
in	O
2016	O
.	O
</s>
<s>
Specifically	O
,	O
the	O
new	O
version	O
of	O
Time	B-Operating_System
Machine	I-Operating_System
makes	O
use	O
of	O
APFS	B-Application
's	O
snapshot	B-Application
technology	O
.	O
</s>
<s>
According	O
to	O
Apple	O
,	O
this	O
enables	O
"	O
faster	O
,	O
more	O
compact	O
,	O
and	O
more	O
reliable	O
backups	B-Application
"	O
than	O
were	O
possible	O
previously	O
with	O
HFS+	B-Application
-formatted	O
drives	O
.	O
</s>
<s>
An	O
independent	O
evaluation	O
of	O
this	O
claim	O
found	O
that	O
macOS	B-Operating_System
11	I-Operating_System
's	O
Time	B-Operating_System
Machine	I-Operating_System
implementation	O
in	O
conjunction	O
with	O
APFS	B-Application
was	O
2.75-fold	O
faster	O
upon	O
initial	O
local	O
backup	B-Application
and	O
4-fold	O
faster	O
upon	O
subsequent	O
backups	B-Application
relative	O
to	O
macOS	B-Application
10.15	O
'	O
s	O
Time	B-Operating_System
Machine	I-Operating_System
implementation	O
using	O
HFS+	B-Application
.	O
</s>
<s>
A	O
more	O
modest	O
yet	O
nevertheless	O
significant	O
advantage	O
was	O
noted	O
as	O
well	O
for	O
backups	B-Application
to	O
network-attached	O
disks	O
.	O
</s>
<s>
USB	B-Protocol
-	O
or	O
Thunderbolt-connected	O
)	O
and	O
network-connected	O
Time	B-Operating_System
Machine	I-Operating_System
backup	B-Application
destinations	O
are	O
formatted	O
as	O
APFS	B-Application
by	O
default	O
,	O
though	O
Time	B-Operating_System
Machine	I-Operating_System
can	O
continue	O
backing	O
up	O
to	O
existing	O
HFS+	B-Application
backup	B-Application
volumes.	O
"	O
</s>
<s>
There	O
is	O
no	O
option	O
to	O
convert	O
existing	O
,	O
HFS+	B-Application
-based	O
backups	B-Application
to	O
APFS	B-Application
;	O
instead	O
,	O
users	O
who	O
want	O
to	O
benefit	O
from	O
the	O
advantages	O
of	O
the	O
new	O
,	O
APFS-based	O
implementation	O
of	O
Time	B-Operating_System
Machine	I-Operating_System
need	O
to	O
start	O
with	O
a	O
fresh	O
volume	O
.	O
</s>
<s>
At	O
least	O
in	O
some	O
circumstances	O
,	O
encryption	O
appears	O
to	O
be	O
required	O
(	O
instead	O
of	O
merely	O
optional	O
)	O
in	O
the	O
new	O
version	O
of	O
Time	B-Operating_System
Machine	I-Operating_System
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
's	O
user	B-Application
interface	I-Application
when	O
retrieving	O
a	O
file	O
uses	O
Apple	O
's	O
Core	B-Operating_System
Animation	I-Operating_System
API	B-Application
.	O
</s>
<s>
Upon	O
its	O
launch	O
,	O
Time	B-Operating_System
Machine	I-Operating_System
"	O
floats	O
"	O
the	O
active	O
Finder	B-Application
or	O
application	O
window	O
from	O
the	O
user	O
's	O
desktop	O
to	O
a	O
backdrop	O
depicting	O
the	O
user	O
's	O
blurred	O
desktop	O
wallpaper	O
.	O
</s>
<s>
Behind	O
the	O
current	O
active	O
window	O
are	O
stacked	O
windows	O
,	O
with	O
each	O
window	O
representing	O
a	O
snapshot	B-Application
of	O
how	O
that	O
folder	O
or	O
application	O
looked	O
on	O
the	O
given	O
date	O
and	O
time	O
in	O
the	O
past	O
.	O
</s>
<s>
When	O
toggling	O
through	O
the	O
previous	O
snapshots	B-Application
,	O
the	O
stacked	O
windows	O
extend	O
backwards	O
,	O
giving	O
the	O
impression	O
of	O
flying	O
through	O
a	O
"	O
time	O
tunnel.	O
"	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
works	O
with	O
locally	O
connected	O
storage	O
disks	O
,	O
which	O
must	O
be	O
formatted	O
in	O
the	O
APFS	B-Application
or	O
HFS+	B-Application
volume	O
formats	O
.	O
</s>
<s>
Support	O
for	O
backing	O
up	O
to	O
APFS	B-Application
volumes	O
was	O
added	O
with	O
macOS	B-Operating_System
11	I-Operating_System
Big	I-Operating_System
Sur	I-Operating_System
and	O
since	O
then	O
APFS	B-Application
is	O
the	O
default	O
volume	O
format	O
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
also	O
works	O
with	O
remote	O
storage	O
media	O
shared	O
from	O
other	O
systems	O
,	O
including	O
Time	B-Device
Capsule	I-Device
,	O
via	O
the	O
network	O
.	O
</s>
<s>
When	O
using	O
remote	O
storage	O
,	O
Time	B-Operating_System
Machine	I-Operating_System
uses	O
sparse	B-Operating_System
bundles	I-Operating_System
.	O
</s>
<s>
This	O
acts	O
as	O
an	O
isolation	O
layer	O
,	O
which	O
makes	O
the	O
storage	O
neutral	O
to	O
the	O
actual	O
file	B-Application
system	I-Application
used	O
by	O
the	O
network	O
server	O
,	O
and	O
also	O
permits	O
the	O
replication	O
of	O
the	O
backup	B-Application
from	O
one	O
storage	O
medium	O
to	O
another	O
.	O
</s>
<s>
Sparse	B-Operating_System
bundles	I-Operating_System
are	O
mounted	O
by	O
macOS	B-Application
like	O
any	O
other	O
device	O
,	O
presenting	O
their	O
content	O
as	O
a	O
HFS+	B-Application
formatted	O
volume	O
,	O
functionally	O
similar	O
to	O
a	O
local	O
storage	O
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
places	O
strict	O
requirements	O
on	O
the	O
backup	B-Application
storage	O
medium	O
.	O
</s>
<s>
A	O
storage	O
drive	O
or	O
partition	O
connected	O
directly	O
to	O
the	O
computer	O
,	O
either	O
internally	O
or	O
by	O
a	O
bus	O
like	O
USB	B-Protocol
or	O
Thunderbolt	B-Protocol
and	O
formatted	O
as	O
APFS	B-Application
or	O
journaled	B-Application
HFS+	B-Application
.	O
</s>
<s>
If	O
the	O
volume	O
format	O
is	O
not	O
correct	O
,	O
Time	B-Operating_System
Machine	I-Operating_System
will	O
prompt	O
the	O
user	O
to	O
reformat	O
it	O
.	O
</s>
<s>
A	O
drive	O
shared	O
by	O
an	O
Apple	B-Device
Time	I-Device
Capsule	I-Device
on	O
the	O
same	O
network	O
.	O
</s>
<s>
A	O
drive	O
connected	O
to	O
an	O
Apple	B-Device
AirPort	I-Device
Extreme	I-Device
802.11ac	O
model	O
on	O
the	O
same	O
network	O
.	O
</s>
<s>
(	O
Earlier	O
generations	O
of	O
the	O
AirPort	B-Device
Extreme	I-Device
are	O
not	O
supported	O
.	O
)	O
</s>
<s>
Local	O
network	O
volumes	O
connected	O
using	O
the	O
Apple	B-Protocol
Filing	I-Protocol
Protocol	I-Protocol
or	O
via	O
an	O
SMB3	O
share	O
that	O
advertises	O
a	O
number	O
of	O
capabilities	O
.	O
</s>
<s>
On	O
a	O
Time	B-Device
Capsule	I-Device
,	O
the	O
backup	B-Application
data	O
is	O
stored	O
in	O
an	O
HFS+	B-Application
disk	B-Application
image	I-Application
and	O
accessed	O
via	O
Apple	B-Protocol
Filing	I-Protocol
Protocol	I-Protocol
.	O
</s>
<s>
Although	O
it	O
is	O
not	O
officially	O
supported	O
,	O
users	O
and	O
manufacturers	O
have	O
also	O
configured	O
FreeBSD	B-Operating_System
and	O
Linux	B-Application
servers	O
and	O
network-attached	B-Application
storage	I-Application
systems	O
to	O
serve	O
Time	O
Machine-enabled	O
Macs	O
.	O
</s>
<s>
There	O
are	O
also	O
a	O
few	O
software	O
tools	O
available	O
on	O
the	O
market	O
that	O
can	O
copy	O
files	O
inside	O
Time	B-Operating_System
Machine	I-Operating_System
backups	B-Application
in	O
Windows	O
machines	O
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
creates	O
a	O
folder	O
on	O
the	O
designated	O
Time	B-Operating_System
Machine	I-Operating_System
volume	O
(	O
local	O
or	O
inside	O
a	O
remote	O
sparse	B-Operating_System
image	I-Operating_System
)	O
into	O
which	O
it	O
copies	O
the	O
directory	O
tree	O
of	O
all	O
locally	O
attached	O
storage	O
drives	O
,	O
except	O
for	O
files	O
and	O
directories	O
that	O
the	O
user	O
has	O
specified	O
to	O
omit	O
,	O
including	O
the	O
Time	B-Operating_System
Machine	I-Operating_System
volume	O
itself	O
.	O
</s>
<s>
Every	O
hour	O
thereafter	O
,	O
it	O
creates	O
a	O
new	O
subordinate	O
folder	O
and	O
copies	O
only	O
files	O
that	O
have	O
changed	O
since	O
the	O
last	O
backup	B-Application
and	O
creates	O
(	O
in	O
the	O
case	O
of	O
HFS+	B-Application
volumes	O
)	O
hard	B-Application
links	I-Application
to	O
files	O
that	O
already	O
exist	O
on	O
the	O
backup	B-Application
drive	O
.	O
</s>
<s>
Some	O
other	O
backup	B-Application
utilities	O
save	O
deltas	O
for	O
file	O
changes	O
,	O
much	O
like	O
version	B-Architecture
control	I-Architecture
systems	I-Architecture
.	O
</s>
<s>
Such	O
an	O
approach	O
permits	O
more	O
frequent	O
backups	B-Application
of	O
minor	O
changes	O
,	O
but	O
can	O
often	O
complicate	O
the	O
interaction	O
with	O
the	O
backup	B-Application
volume	O
.	O
</s>
<s>
By	O
contrast	O
,	O
it	O
is	O
possible	O
to	O
manually	O
browse	O
a	O
Time	B-Operating_System
Machine	I-Operating_System
backup	B-Application
volume	O
without	O
using	O
the	O
Time	B-Operating_System
Machine	I-Operating_System
interface	O
;	O
Time	B-Operating_System
Machine	I-Operating_System
presents	O
each	O
backup	B-Application
to	O
the	O
user	O
as	O
a	O
complete	O
disk	O
copy	O
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
on	O
HFS+	B-Application
volumes	O
creates	O
multiple	O
hard	B-Application
links	I-Application
to	O
unmodified	O
directories	O
.	O
</s>
<s>
Multiple	O
linking	O
of	O
directories	O
is	O
a	O
peculiar	O
feature	O
for	O
HFS+	B-Application
,	O
and	O
is	O
not	O
supported	O
on	O
modern	O
Unix	O
file	B-Application
systems	I-Application
including	O
Apple	O
's	O
own	O
APFS	B-Application
.	O
</s>
<s>
As	O
a	O
result	O
,	O
tools	O
like	O
rsync	B-Application
cannot	O
be	O
used	O
to	O
replicate	O
a	O
Time	B-Operating_System
Machine	I-Operating_System
volume	O
;	O
replication	O
can	O
only	O
reliably	O
be	O
done	O
by	O
imaging	O
the	O
entire	O
filesystem	B-Application
.	O
</s>
<s>
This	O
means	O
that	O
instead	O
of	O
examining	O
every	O
file	O
's	O
modification	O
date	O
when	O
it	O
is	O
activated	O
,	O
Time	B-Operating_System
Machine	I-Operating_System
only	O
needs	O
to	O
scan	O
the	O
directories	O
that	O
changed	O
for	O
files	O
to	O
copy	O
.	O
</s>
<s>
This	O
differs	O
from	O
the	O
approach	O
taken	O
by	O
similar	O
backup	B-Application
utilities	O
rsync	B-Application
and	O
FlyBack	B-Language
,	O
which	O
examine	O
modification	O
dates	O
of	O
all	O
files	O
during	O
backup	B-Application
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
is	O
also	O
available	O
in	O
the	O
macOS	B-Application
installation	O
process	O
.	O
</s>
<s>
One	O
of	O
the	O
features	O
in	O
the	O
Migration	O
Assistant	O
interface	O
is	O
to	O
restore	O
the	O
contents	O
of	O
a	O
Time	B-Operating_System
Machine	I-Operating_System
backup	B-Application
.	O
</s>
<s>
In	O
other	O
words	O
,	O
a	O
hard	O
drive	O
can	O
be	O
restored	O
from	O
a	O
Time	B-Operating_System
Machine	I-Operating_System
backup	B-Application
in	O
the	O
event	O
of	O
a	O
catastrophic	O
crash	O
.	O
</s>
<s>
OS	B-Operating_System
X	I-Operating_System
Mountain	I-Operating_System
Lion	I-Operating_System
introduced	O
the	O
ability	O
to	O
use	O
multiple	O
volumes	O
simultaneously	O
for	O
Time	B-Operating_System
Machine	I-Operating_System
operations	O
.	O
</s>
<s>
When	O
the	O
user	O
specifies	O
more	O
than	O
one	O
volume	O
to	O
use	O
,	O
macOS	B-Application
rotates	O
among	O
the	O
desired	O
volumes	O
each	O
time	O
it	O
does	O
a	O
backup	B-Application
.	O
</s>
<s>
Time	B-Operating_System
Machine	I-Operating_System
supports	O
two	O
forms	O
of	O
exclusion	O
:	O
one	O
based	O
on	O
a	O
user-configured	O
list	O
of	O
paths	O
(	O
plus	O
a	O
set	O
of	O
system	O
defaults	O
)	O
,	O
the	O
other	O
based	O
on	O
the	O
extended	B-Application
file	I-Application
attribute	I-Application
.	O
</s>
<s>
The	O
attribute	O
should	O
contain	O
the	O
string	O
in	O
any	O
property	B-Application
list	I-Application
format	O
.	O
</s>
<s>
Writing	O
instead	O
sets	O
the	O
exclusion	O
for	O
iOS	O
backups	B-Application
.	O
</s>
<s>
Third-party	O
backup	B-Application
applications	O
that	O
respect	O
this	O
setting	O
include	O
CrashPlan	O
and	O
Arq	O
.	O
</s>
<s>
Apple	O
wraps	O
the	O
attribute	O
into	O
the	O
command-line	O
utility	O
as	O
well	O
as	O
a	O
CoreServices	O
API	B-Application
.	O
</s>
