<s>
In	O
computing	O
,	O
OverlayFS	B-Application
is	O
a	O
union	B-Application
mount	I-Application
filesystem	B-Application
implementation	O
for	O
Linux	B-Application
.	O
</s>
<s>
The	O
need	O
and	O
specification	O
of	O
a	O
kernel	O
mode	O
Linux	B-Application
union	B-Application
mount	I-Application
filesystem	B-Application
was	O
identified	O
in	O
late	O
2009	O
.	O
</s>
<s>
The	O
initial	O
RFC	O
patchset	O
of	O
OverlayFS	B-Application
was	O
submitted	O
by	O
Miklos	O
Szeredi	O
in	O
2010	O
.	O
</s>
<s>
By	O
2011	O
,	O
OpenWrt	B-Application
had	O
already	O
adopted	O
it	O
for	O
their	O
use	O
.	O
</s>
<s>
It	O
was	O
merged	O
into	O
the	O
Linux	B-Application
kernel	O
mainline	O
in	O
2014	O
,	O
in	O
kernel	O
version	O
3.18	O
.	O
</s>
<s>
the	O
storage	O
driver	O
in	O
Docker	B-Language
.	O
</s>
<s>
While	O
most	O
Live	O
CD	O
linux	B-Application
distributions	O
used	O
Aufs	B-Application
as	O
of	O
November	O
2016	O
,	O
Slackware	B-Application
used	O
overlayfs	B-Application
for	O
its	O
live	O
CD	O
.	O
</s>
<s>
The	O
main	O
mechanics	O
of	O
OverlayFS	B-Application
relate	O
to	O
the	O
merging	O
of	O
directory	O
access	O
when	O
both	O
filesystems	B-Application
present	O
a	O
directory	O
for	O
the	O
same	O
name	O
.	O
</s>
<s>
Otherwise	O
,	O
OverlayFS	B-Application
presents	O
the	O
object	O
,	O
if	O
any	O
,	O
yielded	O
by	O
one	O
or	O
the	O
other	O
,	O
with	O
the	O
"	O
upper	O
"	O
filesystem	B-Application
taking	O
precedence	O
.	O
</s>
<s>
Unlike	O
some	O
other	O
overlay	O
filesystems	B-Application
,	O
the	O
directory	O
subtrees	O
being	O
merged	O
by	O
OverlayFS	B-Application
do	O
not	O
necessarily	O
have	O
to	O
be	O
from	O
distinct	O
filesystems	B-Application
.	O
</s>
<s>
OverlayFS	B-Application
supports	O
whiteouts	O
and	O
opaque	O
directories	O
in	O
the	O
upper	O
filesystem	B-Application
to	O
allow	O
file	O
and	O
directory	O
deletion	O
.	O
</s>
<s>
OverlayFS	B-Application
does	O
not	O
support	O
renaming	O
files	O
without	O
performing	O
a	O
full	O
copy-up	O
of	O
the	O
file	O
;	O
however	O
,	O
renaming	O
directories	O
in	O
an	O
upper	O
filesystem	B-Application
has	O
limited	O
support	O
.	O
</s>
<s>
OverlayFS	B-Application
does	O
not	O
support	O
merging	O
changes	O
from	O
an	O
upper	O
filesystem	B-Application
to	O
a	O
lower	O
filesystem	B-Application
.	O
</s>
