<s>
Richacls	B-Operating_System
is	O
a	O
Linux	B-Application
implementation	O
of	O
the	O
NFSv4	O
ACLs	O
which	O
has	O
been	O
extended	O
by	O
file	O
masks	O
to	O
more	O
easily	O
fit	O
the	O
proprietary	O
POSIX	O
draft	O
file	O
permission	O
model	O
.	O
</s>
<s>
Nowadays	O
,	O
they	O
offer	O
the	O
most	O
complex	O
permission	O
model	O
for	O
ext4	B-Application
file	O
system	O
in	O
Linux	B-Application
.	O
</s>
<s>
They	O
are	O
even	O
more	O
complex	O
than	O
POSIX	O
draft	O
ACLs	O
,	O
which	O
means	O
it	O
is	O
not	O
possible	O
to	O
convert	O
back	O
from	O
Richacls	B-Operating_System
to	O
Linux	B-Application
 '	O
implementation	O
of	O
the	O
POSIX	O
draft	O
ACLs	O
without	O
losing	O
information	O
.	O
</s>
<s>
Richacls	B-Operating_System
use	O
ext4	B-Application
extended	B-Application
file	I-Application
attributes	I-Application
(	O
xattrs	B-Application
)	O
to	O
store	O
ACLs	O
.	O
</s>
