<s>
kdump	B-Device
is	O
a	O
feature	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
that	O
creates	O
crash	B-Error_Name
dumps	I-Error_Name
in	O
the	O
event	O
of	O
a	O
kernel	B-Operating_System
crash	I-Operating_System
.	O
</s>
<s>
When	O
triggered	O
,	O
kdump	B-Device
exports	O
a	O
memory	O
image	O
(	O
also	O
known	O
as	O
vmcore	O
)	O
that	O
can	O
be	O
analyzed	O
for	O
the	O
purposes	O
of	O
debugging	O
and	O
determining	O
the	O
cause	O
of	O
a	O
crash	O
.	O
</s>
<s>
The	O
dumped	O
image	O
of	O
main	O
memory	O
,	O
exported	O
as	O
an	O
Executable	O
and	O
Linkable	O
Format	O
(	O
ELF	O
)	O
object	O
,	O
can	O
be	O
accessed	O
either	O
directly	O
through	O
during	O
the	O
handling	O
of	O
a	O
kernel	B-Operating_System
crash	I-Operating_System
,	O
or	O
it	O
can	O
be	O
automatically	O
saved	O
to	O
a	O
locally	O
accessible	O
file	B-Application
system	I-Application
,	O
to	O
a	O
raw	B-Application
device	I-Application
,	O
or	O
to	O
a	O
remote	O
system	O
accessible	O
over	O
network	B-Architecture
.	O
</s>
<s>
In	O
the	O
event	O
of	O
a	O
kernel	B-Operating_System
crash	I-Operating_System
,	O
kdump	B-Device
preserves	O
system	O
consistency	O
by	O
booting	B-Operating_System
another	O
Linux	B-Operating_System
kernel	I-Operating_System
,	O
which	O
is	O
known	O
as	O
the	O
dump-capture	O
kernel	B-Operating_System
,	O
and	O
using	O
it	O
to	O
export	O
and	O
save	O
a	O
memory	B-Error_Name
dump	I-Error_Name
.	O
</s>
<s>
As	O
a	O
result	O
,	O
the	O
system	B-Operating_System
boots	I-Operating_System
into	O
a	O
clean	O
and	O
reliable	O
environment	O
instead	O
of	O
relying	O
on	O
an	O
already	O
crashed	O
kernel	B-Operating_System
that	O
may	O
cause	O
various	O
issues	O
,	O
such	O
as	O
causing	O
file	B-Application
system	I-Application
corruption	O
while	O
writing	O
a	O
memory	B-Error_Name
dump	I-Error_Name
file	O
.	O
</s>
<s>
To	O
implement	O
this	O
"	O
dual	O
kernel	B-Operating_System
"	O
layout	O
,	O
kdump	B-Device
uses	O
kexec	B-Application
for	O
"	O
warm	O
"	O
booting	B-Operating_System
into	O
the	O
dump-capture	O
kernel	B-Operating_System
immediately	O
after	O
the	O
kernel	B-Operating_System
crash	I-Operating_System
,	O
using	O
kexec	B-Application
's	O
ability	O
to	O
boot	B-Operating_System
"	O
over	O
"	O
the	O
currently	O
running	O
kernel	B-Operating_System
while	O
avoiding	O
the	O
execution	O
of	O
a	O
bootloader	B-Application
and	O
hardware	B-Architecture
initialization	O
performed	O
by	O
the	O
system	O
firmware	B-Application
(	O
BIOS	B-Operating_System
or	O
UEFI	B-Architecture
)	O
.	O
</s>
<s>
A	O
dump-capture	O
kernel	B-Operating_System
can	O
be	O
either	O
a	O
separate	O
Linux	B-Operating_System
kernel	B-Operating_System
image	I-Operating_System
built	O
specifically	O
for	O
that	O
purpose	O
,	O
or	O
the	O
primary	O
kernel	B-Operating_System
image	I-Operating_System
can	O
be	O
reused	O
on	O
architectures	B-General_Concept
that	O
support	O
relocatable	B-Library
kernels	B-Operating_System
.	O
</s>
<s>
The	O
contents	O
of	O
main	O
memory	O
(	O
RAM	B-Architecture
)	O
are	O
preserved	O
while	O
booting	B-Operating_System
into	O
and	O
running	O
the	O
dump-capture	O
kernel	B-Operating_System
by	O
reserving	O
a	O
small	O
amount	O
of	O
RAM	B-Architecture
in	O
advance	O
,	O
into	O
which	O
the	O
dump-capture	O
kernel	B-Operating_System
is	O
preloaded	O
so	O
none	O
of	O
the	O
RAM	B-Architecture
used	O
by	O
the	O
primary	O
kernel	B-Operating_System
is	O
overwritten	O
when	O
a	O
kernel	B-Operating_System
crash	I-Operating_System
is	O
handled	O
.	O
</s>
<s>
This	O
reserved	O
amount	O
of	O
RAM	B-Architecture
is	O
used	O
solely	O
by	O
the	O
dump-capture	O
kernel	B-Operating_System
and	O
is	O
otherwise	O
unused	O
during	O
normal	O
system	O
operation	O
.	O
</s>
<s>
Some	O
architectures	B-General_Concept
,	O
including	O
x86	B-Operating_System
and	O
ppc64	B-General_Concept
,	O
require	O
a	O
small	O
fixed-position	O
portion	O
of	O
RAM	B-Architecture
to	O
boot	B-Operating_System
a	O
kernel	B-Operating_System
regardless	O
of	O
where	O
it	O
is	O
loaded	O
;	O
in	O
this	O
case	O
,	O
kexec	B-Application
creates	O
a	O
copy	O
of	O
that	O
portion	O
of	O
RAM	B-Architecture
so	O
it	O
is	O
also	O
accessible	O
to	O
the	O
dump-capture	O
kernel	B-Operating_System
.	O
</s>
<s>
Size	O
and	O
optional	O
position	O
of	O
the	O
reserved	O
portion	O
of	O
RAM	B-Architecture
are	O
specified	O
through	O
the	O
kernel	B-Operating_System
boot	B-Operating_System
parameter	O
,	O
and	O
the	O
command-line	B-Device
utility	I-Device
is	O
used	O
after	O
the	O
primary	O
kernel	B-Operating_System
boots	O
to	O
preload	O
a	O
dump-capture	O
kernel	B-Operating_System
image	I-Operating_System
and	O
its	O
associated	O
initrd	B-Application
image	O
into	O
the	O
reserved	O
portion	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
functionality	O
that	O
is	O
part	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
,	O
additional	O
userspace	B-Operating_System
utilities	O
support	O
the	O
kdump	B-Device
mechanism	O
,	O
including	O
the	O
utility	O
mentioned	O
above	O
.	O
</s>
<s>
Besides	O
the	O
official	O
utilities	O
,	O
which	O
are	O
provided	O
as	O
a	O
patch	O
to	O
the	O
kexec	B-Application
's	O
suite	O
of	O
userspace	B-Operating_System
utilities	O
,	O
some	O
Linux	B-Application
distributions	I-Application
provide	O
additional	O
utilities	O
that	O
simplify	O
the	O
configuration	O
of	O
kdump	B-Device
's	O
operation	O
,	O
including	O
the	O
setup	O
of	O
automated	O
saving	O
of	O
memory	B-Error_Name
dump	I-Error_Name
files	O
.	O
</s>
<s>
Created	O
memory	B-Error_Name
dump	I-Error_Name
files	O
can	O
be	O
analyzed	O
using	O
the	O
GNU	B-Language
Debugger	I-Language
(	O
)	O
,	O
or	O
by	O
using	O
Red	O
Hat	O
's	O
dedicated	O
utility	O
.	O
</s>
<s>
kdump	B-Device
functionality	O
,	O
together	O
with	O
kexec	B-Application
,	O
was	O
merged	O
into	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
mainline	O
in	O
kernel	B-Operating_System
version	O
2.6.13	O
,	O
which	O
was	O
released	O
on	O
August	O
29	O
,	O
2005	O
.	O
</s>
