<s>
Xvfb	B-Device
or	O
X	B-Operating_System
virtual	B-Application
framebuffer	O
is	O
a	O
display	O
server	O
implementing	O
the	O
X11	B-Operating_System
display	O
server	O
protocol	O
.	O
</s>
<s>
In	O
contrast	O
to	O
other	O
display	O
servers	O
,	O
Xvfb	B-Device
performs	O
all	O
graphical	O
operations	O
in	O
virtual	B-Application
memory	O
without	O
showing	O
any	O
screen	B-Device
output	O
.	O
</s>
<s>
From	O
the	O
point	O
of	O
view	O
of	O
the	O
client	B-Protocol
,	O
it	O
acts	O
exactly	O
like	O
any	O
other	O
X	B-Operating_System
display	I-Operating_System
server	I-Operating_System
,	O
serving	O
requests	O
and	O
sending	O
events	O
and	O
errors	O
as	O
appropriate	O
.	O
</s>
<s>
This	O
virtual	B-Application
server	O
does	O
not	O
require	O
the	O
computer	O
it	O
is	O
running	O
on	O
to	O
have	O
any	O
kind	O
of	O
graphics	B-Device
adapter	I-Device
,	O
a	O
screen	B-Device
or	O
any	O
input	B-Device
device	I-Device
.	O
</s>
<s>
Only	O
a	O
network	B-Architecture
layer	O
is	O
necessary	O
.	O
</s>
<s>
Xvfb	B-Device
is	O
primarily	O
used	O
for	O
testing	O
:	O
</s>
<s>
Since	O
it	O
shares	O
code	O
with	O
the	O
real	O
X	B-Operating_System
server	O
,	O
it	O
can	O
be	O
used	O
to	O
test	O
the	O
parts	O
of	O
the	O
code	O
that	O
are	O
not	O
related	O
to	O
the	O
specific	O
hardware	O
.	O
</s>
<s>
It	O
can	O
be	O
used	O
to	O
test	O
clients	O
in	O
various	O
conditions	O
that	O
would	O
otherwise	O
require	O
a	O
range	O
of	O
different	O
hardware	O
;	O
for	O
example	O
,	O
it	O
can	O
be	O
used	O
to	O
test	O
whether	O
clients	O
work	O
correctly	O
at	O
depths	O
or	O
screen	B-Device
sizes	O
that	O
are	O
rarely	O
supported	O
by	O
hardware	O
.	O
</s>
<s>
Running	O
programs	O
that	O
require	O
an	O
X	B-Operating_System
server	O
to	O
be	O
active	O
even	O
when	O
they	O
do	O
not	O
use	O
it	O
.	O
</s>
<s>
As	O
an	O
example	O
,	O
the	O
following	O
sequence	O
of	O
commands	O
runs	O
a	O
virtual	B-Application
framebuffer	O
X	B-Operating_System
server	O
as	O
display	O
:1	O
,	O
runs	O
a	O
program	O
on	O
it	O
,	O
and	O
captures	O
the	O
virtual	B-Application
screen	B-Device
in	O
the	O
file	O
image.png	O
using	O
the	O
import	O
command	O
of	O
ImageMagick	B-Language
:	O
</s>
<s>
The	O
result	O
can	O
be	O
shown	O
by	O
running	O
the	O
ImageMagick	B-Language
display	O
program	O
(	O
display	O
image.png	O
)	O
or	O
xv	O
(	O
xv	O
image.png	O
)	O
.	O
</s>
<s>
The	O
program	O
xvfb-run	O
is	O
often	O
used	O
to	O
automate	O
the	O
process	O
of	O
finding	O
an	O
available	O
display	O
and	O
managing	O
authentication	O
.	O
</s>
<s>
Xvfb	B-Device
is	O
also	O
used	O
for	O
remote	O
control	O
.	O
</s>
<s>
VNC	B-Protocol
over	O
SSH	B-Protocol
is	O
slightly	O
faster	O
than	O
X11	B-Operating_System
over	O
SSH	B-Protocol
.	O
</s>
<s>
In	O
this	O
case	O
,	O
Xvfb	B-Device
is	O
often	O
combined	O
with	O
a	O
lightweight	O
window	O
manager	O
(	O
such	O
as	O
Fluxbox	B-Language
or	O
Openbox	B-Language
)	O
and	O
a	O
VNC	B-Protocol
server	I-Protocol
such	O
as	O
X11vnc	B-Application
.	O
</s>
<s>
The	O
next	O
step	O
is	O
to	O
fire	O
up	O
a	O
SSH	B-Protocol
client	B-Protocol
such	O
as	O
PuTTY	B-Operating_System
with	O
tunneling	O
to	O
localhost	O
port	B-Protocol
5900	I-Protocol
enabled	O
.	O
</s>
<s>
x11vnc	B-Application
's	O
man	B-Protocol
page	I-Protocol
also	O
contains	O
instructions	O
.	O
</s>
<s>
Xvnc	O
(	O
not	O
to	O
be	O
confused	O
with	O
x11vnc	B-Application
)	O
is	O
very	O
similar	O
to	O
Xvfb	B-Device
.	O
</s>
