<s>
Fossil	B-Application
is	O
the	O
default	O
file	B-Application
system	I-Application
in	O
Plan	B-Operating_System
9	I-Operating_System
from	I-Operating_System
Bell	I-Operating_System
Labs	I-Operating_System
.	O
</s>
<s>
It	O
serves	O
the	O
network	O
protocol	O
9P	B-Operating_System
and	O
runs	O
as	O
a	O
user	B-Operating_System
space	I-Operating_System
daemon	B-Operating_System
,	O
like	O
most	O
Plan	B-Operating_System
9	I-Operating_System
file	O
servers	O
.	O
</s>
<s>
Fossil	B-Application
is	O
different	O
from	O
most	O
other	O
file	B-Application
systems	I-Application
due	O
to	O
its	O
snapshot/archival	O
feature	O
.	O
</s>
<s>
It	O
can	O
take	O
snapshots	B-Application
of	O
the	O
entire	O
file	B-Application
system	I-Application
on	O
command	O
or	O
automatically	O
(	O
at	O
a	O
user-set	O
interval	O
)	O
.	O
</s>
<s>
These	O
snapshots	B-Application
can	O
be	O
kept	O
on	O
the	O
Fossil	B-Application
partition	B-Application
as	O
long	O
as	O
disk	O
space	O
allows	O
;	O
if	O
the	O
partition	B-Application
fills	O
up	O
then	O
old	O
snapshots	B-Application
will	O
be	O
removed	O
to	O
free	O
up	O
disk	O
space	O
.	O
</s>
<s>
A	O
snapshot	B-Application
can	O
also	O
be	O
saved	O
permanently	O
to	O
Venti	B-Application
.	O
</s>
<s>
Fossil	B-Application
and	O
Venti	B-Application
are	O
typically	O
installed	O
together	O
.	O
</s>
<s>
Snapshots	B-Application
are	O
available	O
to	O
all	O
users	O
.	O
</s>
<s>
(	O
This	O
is	O
possible	O
because	O
Fossil	B-Application
enforces	O
file	O
permissions	O
;	O
users	O
can	O
only	O
access	O
data	O
which	O
they	O
would	O
be	O
allowed	O
to	O
access	O
anyway	O
;	O
thus	O
a	O
user	O
cannot	O
snoop	O
on	O
another	O
's	O
old	O
files	O
or	O
look	O
at	O
old	O
passwords	O
or	O
such	O
.	O
)	O
</s>
<s>
Data	O
in	O
permanent	O
snapshots	B-Application
(	O
sometimes	O
called	O
archives	O
)	O
cannot	O
be	O
modified	O
.	O
</s>
<s>
Only	O
the	O
non-permanent	O
snapshots	B-Application
can	O
be	O
removed	O
.	O
</s>
<s>
To	O
access	O
a	O
snapshot	B-Application
,	O
one	O
would	O
connect	O
to	O
a	O
running	O
fossil	B-Application
instance	O
(	O
“	O
mount	O
”	O
it	O
)	O
and	O
change	O
directory	B-Application
to	O
the	O
desired	O
snapshot	B-Application
,	O
e.g.	O
</s>
<s>
/snapshot/yyyy/mmdd/hhmm	O
(	O
with	O
yyyy	O
,	O
mm	O
,	O
dd	O
,	O
hh	O
,	O
mm	O
meaning	O
year	O
,	O
month	O
,	O
day	O
,	O
hour	O
,	O
minute	O
)	O
.	O
</s>
<s>
To	O
access	O
an	O
archive	O
(	O
permanent	O
snapshot	B-Application
)	O
,	O
a	O
directory	B-Application
of	O
the	O
form	O
/archive/yyyy/mmdds	O
(	O
with	O
yyyy	O
,	O
mm	O
,	O
dd	O
,	O
s	O
meaning	O
year	O
,	O
month	O
,	O
day	O
,	O
sequence	O
number	O
)	O
would	O
be	O
used	O
.	O
</s>
<s>
Plan	B-Operating_System
9	I-Operating_System
allows	O
modifying	O
the	O
namespace	O
in	O
advanced	O
ways	O
,	O
like	O
redirecting	O
one	O
path	O
to	O
another	O
path	O
(	O
e.g.	O
</s>
<s>
Fossil	B-Application
is	O
available	O
on	O
several	O
other	O
platforms	O
via	O
Plan	B-Application
9	I-Application
from	I-Application
User	I-Application
Space	I-Application
.	O
</s>
<s>
Fossil	B-Application
was	O
designed	O
and	O
implemented	O
by	O
Sean	O
Quinlan	O
,	O
Jim	O
McKie	O
and	O
Russ	O
Cox	O
at	O
Bell	O
Labs	O
and	O
added	O
to	O
the	O
Plan	B-Operating_System
9	I-Operating_System
distribution	O
at	O
the	O
end	O
of	O
2002	O
.	O
</s>
<s>
It	O
became	O
the	O
default	O
file	B-Application
system	I-Application
in	O
2003	O
,	O
replacing	O
Kfs	O
and	O
the	O
previous	O
Plan	B-Operating_System
9	I-Operating_System
archival	O
file	B-Application
system	I-Application
,	O
dubbed	O
The	O
Plan	B-Operating_System
9	I-Operating_System
File	O
Server	O
,	O
or	O
"	O
fs	O
"	O
.	O
</s>
<s>
fs	O
is	O
also	O
an	O
archival	O
file	B-Application
system	I-Application
which	O
originally	O
was	O
designed	O
to	O
store	O
data	O
on	O
a	O
WORM	B-Device
optical	O
disc	O
system	O
.	O
</s>
<s>
The	O
permanent	O
storage	O
for	O
fossil	B-Application
is	O
provided	O
by	O
Venti	B-Application
,	O
which	O
typically	O
stores	O
data	O
on	O
hard	O
drives	O
,	O
which	O
have	O
much	O
lower	O
access	O
times	O
than	O
optical	O
discs	O
.	O
</s>
