<s>
A	O
headless	B-Application
computer	I-Application
is	O
a	O
computer	O
system	O
or	O
device	O
that	O
has	O
been	O
configured	O
to	O
operate	O
without	O
a	O
monitor	B-Device
(	O
the	O
missing	O
"	O
head	O
"	O
)	O
,	O
keyboard	B-Device
,	O
and	O
mouse	B-Device
.	O
</s>
<s>
A	O
headless	B-Application
system	I-Application
is	O
typically	O
controlled	O
over	O
a	O
network	O
connection	O
,	O
although	O
some	O
headless	B-Application
system	I-Application
devices	O
require	O
a	O
serial	O
connection	O
to	O
be	O
made	O
over	O
RS-232	O
for	O
administration	O
of	O
the	O
device	O
.	O
</s>
<s>
During	O
bootup	B-Operating_System
,	O
some	O
(	O
especially	O
older	O
)	O
PC	B-Operating_System
BIOS	I-Operating_System
versions	O
will	O
wait	O
indefinitely	O
for	O
a	O
user	O
to	O
press	O
a	O
key	O
before	O
proceeding	O
.	O
</s>
<s>
If	O
some	O
basic	O
device	O
,	O
such	O
as	O
a	O
video	B-Device
card	I-Device
or	O
keyboard	B-Device
,	O
are	O
not	O
installed	O
or	O
connected	O
,	O
this	O
could	O
effectively	O
halt	O
an	O
unattended	O
system	O
.	O
</s>
<s>
On	O
more	O
modern	O
systems	O
,	O
the	O
BIOS	B-Operating_System
factory	O
setting	O
will	O
typically	O
be	O
configured	O
to	O
behave	O
this	O
way	O
as	O
well	O
,	O
but	O
this	O
setting	O
can	O
be	O
changed	O
with	O
a	O
BIOS	B-Operating_System
setup	O
utility	O
to	O
proceed	O
without	O
user	O
intervention	O
.	O
</s>
<s>
Even	O
in	O
cases	O
where	O
a	O
system	O
has	O
been	O
set	O
up	O
to	O
be	O
managed	O
remotely	O
,	O
a	O
local	O
keyboard	B-Device
and	O
video	B-Device
card	I-Device
may	O
still	O
be	O
needed	O
from	O
time	O
to	O
time	O
;	O
for	O
example	O
,	O
to	O
diagnose	O
boot	B-Operating_System
problems	O
that	O
occur	O
before	O
a	O
remote	O
access	O
application	O
is	O
initialized	O
.	O
</s>
<s>
Some	O
servers	O
provide	O
for	O
remote	O
control	O
with	O
an	O
internal	O
network	B-Protocol
card	I-Protocol
and	O
hardware	O
that	O
mirrors	O
the	O
console	O
screen	O
.	O
</s>
<s>
For	O
example	O
,	O
HP	O
offers	O
a	O
system	O
called	O
Integrated	B-Device
Lights-Out	I-Device
(	O
iLO	O
)	O
that	O
provides	O
this	O
function	O
.	O
</s>
<s>
Another	O
hardware	O
solution	O
is	O
to	O
use	O
a	O
KVM-over-IP	B-Device
switch	O
.	O
</s>
<s>
Such	O
a	O
switch	O
is	O
a	O
traditional	O
Keyboard-Video-Mouse	O
device	O
with	O
the	O
added	O
ability	O
to	O
provide	O
remote	O
control	O
sessions	O
over	O
IP	O
.	O
</s>
<s>
Administration	O
of	O
a	O
headless	B-Application
system	I-Application
typically	O
takes	O
place	O
with	O
a	O
text-based	O
interface	O
such	O
as	O
a	O
command	B-Application
line	I-Application
in	O
Unix	B-Application
or	O
in	O
Linux	B-Application
.	O
</s>
<s>
These	O
interfaces	O
,	O
often	O
called	O
"	O
virtual	B-Application
terminals	I-Application
"	O
or	O
"	O
terminal	B-Application
emulators	I-Application
"	O
,	O
attempt	O
to	O
simulate	O
the	O
behavior	O
of	O
"	O
real	O
"	O
interface	O
terminals	O
like	O
the	O
Digital	O
Equipment	O
Corporation	O
's	O
VT100	B-Device
,	O
but	O
over	O
networks	O
,	O
usually	O
using	O
protocols	O
such	O
as	O
Secure	B-Protocol
Shell	I-Protocol
.	O
</s>
<s>
One	O
can	O
also	O
use	O
systems	O
such	O
as	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
and	O
VNC	B-Protocol
combined	O
with	O
virtual	O
display	O
drivers	O
-	O
this	O
setup	O
allows	O
remote	O
connections	O
to	O
headless	B-Application
machines	I-Application
through	O
ordinary	O
graphical	B-Application
user	I-Application
interfaces	I-Application
,	O
often	O
running	O
over	O
network	O
protocols	O
like	O
TCP/IP	B-Protocol
.	O
</s>
