<s>
dmesg	B-Device
(	O
diagnostic	O
messages	O
)	O
is	O
a	O
command	B-Application
on	O
most	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
that	O
prints	O
the	O
message	O
buffer	B-General_Concept
of	O
the	O
kernel	B-Operating_System
.	O
</s>
<s>
The	O
output	O
includes	O
messages	O
produced	O
by	O
the	O
device	B-Application
drivers	I-Application
.	O
</s>
<s>
When	O
initially	O
booted	B-Operating_System
,	O
a	O
computer	O
system	O
loads	O
its	O
kernel	B-Operating_System
into	O
memory	O
.	O
</s>
<s>
At	O
this	O
stage	O
device	B-Application
drivers	I-Application
present	O
in	O
the	O
kernel	B-Operating_System
are	O
set	O
up	O
to	O
drive	O
relevant	O
hardware	O
.	O
</s>
<s>
Such	O
drivers	O
,	O
as	O
well	O
as	O
other	O
elements	O
within	O
the	O
kernel	B-Operating_System
,	O
may	O
produce	O
output	O
(	O
"	O
messages	O
"	O
)	O
reporting	O
both	O
the	O
presence	O
of	O
modules	O
and	O
the	O
values	O
of	O
any	O
parameters	O
adopted	O
.	O
</s>
<s>
(	O
It	O
may	O
be	O
possible	O
to	O
specify	O
boot	B-Operating_System
parameters	O
which	O
control	O
the	O
level	O
of	O
detail	O
in	O
the	O
messages	O
.	O
)	O
</s>
<s>
The	O
booting	B-Operating_System
process	O
typically	O
happens	O
at	O
a	O
speed	O
where	O
individual	O
messages	O
scroll	O
off	O
the	O
top	O
of	O
the	O
screen	O
before	O
an	O
operator	O
can	O
read/digest	O
them	O
.	O
</s>
<s>
The	O
command	B-Application
allows	O
the	O
review	O
of	O
such	O
messages	O
in	O
a	O
controlled	O
manner	O
after	O
the	O
system	O
has	O
started	O
.	O
</s>
<s>
Even	O
after	O
the	O
system	O
has	O
fully	O
booted	B-Operating_System
,	O
the	O
kernel	B-Operating_System
may	O
occasionally	O
produce	O
further	O
diagnostic	O
messages	O
.	O
</s>
<s>
Common	O
examples	O
of	O
when	O
this	O
might	O
happen	O
are	O
when	O
I/O	O
devices	O
encounter	O
errors	O
,	O
or	O
USB	B-Protocol
devices	I-Protocol
are	O
hot-plugged	B-Device
.	O
</s>
<s>
dmesg	B-Device
provides	O
a	O
mechanism	O
to	O
review	O
these	O
messages	O
at	O
a	O
later	O
time	O
.	O
</s>
<s>
When	O
first	O
produced	O
,	O
they	O
will	O
be	O
directed	O
to	O
the	O
system	B-Device
console	I-Device
.	O
</s>
<s>
The	O
output	O
of	O
dmesg	B-Device
can	O
amount	O
to	O
many	O
complete	O
screens	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
this	O
output	O
is	O
normally	O
reviewed	O
using	O
standard	O
text-manipulation	O
tools	O
such	O
as	O
more	B-Device
,	O
tail	B-Application
,	O
less	B-Application
or	O
grep	B-Application
.	O
</s>
<s>
Size	O
of	O
the	O
dmesg	B-Device
buffer	B-General_Concept
is	O
limited	O
and	O
the	O
output	O
is	O
often	O
captured	O
in	O
a	O
permanent	O
system	O
logfile	O
via	O
a	O
logging	O
daemon	O
,	O
such	O
as	O
syslog	B-Protocol
.	O
</s>
<s>
Traditionally	O
,	O
dmesg	B-Device
lines	O
begin	O
with	O
a	O
device	B-Application
name	I-Application
followed	O
by	O
a	O
colon	O
,	O
followed	O
with	O
detailed	O
text	O
.	O
</s>
<s>
Each	O
cluster	O
is	O
usually	O
associated	O
with	O
a	O
single	O
device	O
enumeration	O
,	O
by	O
one	O
particular	O
device	B-Application
driver	I-Application
(	O
or	O
device	O
facility	O
)	O
associated	O
with	O
the	O
device	B-Application
name	I-Application
.	O
</s>
<s>
Device	B-Application
drivers	I-Application
may	O
specify	O
the	O
format	O
in	O
the	O
manual	B-Protocol
page	I-Protocol
by	O
convention	O
called	O
identically	O
to	O
the	O
device	B-Application
file	I-Application
name	O
without	O
the	O
trailing	O
number	O
.	O
</s>
