<s>
vmlinux	B-Application
is	O
a	O
statically	B-Library
linked	I-Library
executable	B-Application
file	I-Application
that	O
contains	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
in	O
one	O
of	O
the	O
object	B-Application
file	I-Application
formats	I-Application
supported	O
by	O
Linux	B-Operating_System
,	O
which	O
includes	O
Executable	B-Application
and	O
Linkable	O
Format	O
(	O
ELF	O
)	O
and	O
Common	O
Object	B-Application
File	I-Application
Format	I-Application
(	O
COFF	O
)	O
.	O
</s>
<s>
The	O
vmlinux	B-Application
file	O
might	O
be	O
required	O
for	O
kernel	B-Operating_System
debugging	O
,	O
symbol	B-Application
table	I-Application
generation	O
or	O
other	O
operations	O
,	O
but	O
must	O
be	O
made	O
bootable	O
before	O
being	O
used	O
as	O
an	O
operating	B-Operating_System
system	I-Operating_System
kernel	I-Operating_System
by	O
adding	O
a	O
multiboot	O
header	O
,	O
bootsector	B-Device
and	O
setup	O
routines	O
.	O
</s>
<s>
Traditionally	O
,	O
UNIX	B-Application
platforms	O
called	O
the	O
kernel	B-Operating_System
image	I-Operating_System
/unix	O
.	O
</s>
<s>
With	O
the	O
development	O
of	O
virtual	B-Architecture
memory	I-Architecture
,	O
kernels	B-Operating_System
that	O
supported	O
this	O
feature	O
were	O
given	O
the	O
vm	O
-	O
prefix	O
to	O
differentiate	O
them	O
.	O
</s>
<s>
The	O
name	O
vmlinux	B-Application
is	O
a	O
mutation	O
of	O
vmunix	O
,	O
while	O
in	O
vmlinuz	B-Application
the	O
letter	O
z	O
at	O
the	O
end	O
denotes	O
that	O
it	O
is	O
compressed	B-General_Concept
(	O
for	O
example	O
gzipped	O
)	O
.	O
</s>
<s>
Traditionally	O
,	O
the	O
kernel	B-Operating_System
was	O
located	O
in	O
the	O
root	B-Application
directory	I-Application
of	O
the	O
filesystem	O
hierarchy	O
;	O
however	O
,	O
as	O
the	O
bootloader	B-Application
must	O
use	O
BIOS	B-Operating_System
drivers	O
to	O
access	O
the	O
hard	B-Device
disk	I-Device
,	O
limitations	O
on	O
some	O
i386	B-General_Concept
systems	O
meant	O
only	O
the	O
first	B-Device
1024	I-Device
cylinders	I-Device
of	O
the	O
hard	B-Device
disk	I-Device
were	O
addressable	O
.	O
</s>
<s>
To	O
overcome	O
this	O
,	O
Linux	B-Operating_System
distributors	O
encouraged	O
users	O
to	O
create	O
a	O
partition	B-Application
at	O
the	O
beginning	O
of	O
their	O
drives	O
specifically	O
for	O
storing	O
bootloader	B-Application
and	O
kernel-related	O
files	O
.	O
</s>
<s>
GRUB	B-Application
,	O
LILO	B-Application
and	O
SYSLINUX	B-Application
are	O
common	O
bootloaders	B-Application
.	O
</s>
<s>
By	O
convention	O
,	O
this	O
partition	B-Application
is	O
mounted	O
on	O
the	O
filesystem	O
hierarchy	O
as	O
/boot	O
.	O
</s>
<s>
This	O
was	O
later	O
standardised	O
by	O
the	O
Filesystem	B-Application
Hierarchy	I-Application
Standard	I-Application
(	O
FHS	O
)	O
,	O
which	O
now	O
requires	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
image	O
to	O
be	O
located	O
in	O
either	O
/	O
or	O
/boot	O
,	O
although	O
there	O
is	O
no	O
technical	O
restriction	O
enforcing	O
this	O
.	O
</s>
<s>
Traditionally	O
,	O
when	O
creating	O
a	O
bootable	O
kernel	B-Operating_System
image	I-Operating_System
,	O
the	O
kernel	B-Operating_System
is	O
also	O
compressed	B-General_Concept
using	O
gzip	B-Application
,	O
or	O
,	O
since	O
Linux	O
2.6.30	O
,	O
using	O
LZMA	B-General_Concept
or	O
bzip2	B-Application
,	O
which	O
requires	O
a	O
very	O
small	O
decompression	B-General_Concept
stub	O
to	O
be	O
included	O
in	O
the	O
resulting	O
image	O
.	O
</s>
<s>
The	O
stub	O
decompresses	O
the	O
kernel	B-Operating_System
code	O
,	O
on	O
some	O
systems	O
printing	O
dots	O
to	O
the	O
console	O
to	O
indicate	O
progress	O
,	O
and	O
then	O
continues	O
the	O
boot	O
process	O
.	O
</s>
<s>
Support	O
for	O
LZO	B-Language
,	O
xz	O
,	O
LZ4	B-Language
and	O
zstd	B-Language
compression	O
was	O
added	O
later	O
.	O
</s>
<s>
The	O
decompression	B-General_Concept
routine	O
is	O
a	O
negligible	O
factor	O
in	O
boot	O
time	O
,	O
and	O
prior	O
to	O
the	O
development	O
of	O
the	O
bzImage	B-Application
,	O
the	O
size	O
constraints	O
of	O
some	O
architectures	O
,	O
notably	O
i386	B-General_Concept
,	O
were	O
extremely	O
limiting	O
,	O
making	O
compression	O
a	O
necessity	O
.	O
</s>
<s>
On	O
the	O
SPARC	B-Architecture
architecture	O
,	O
the	O
vmlinux	B-Application
file	O
is	O
compressed	B-General_Concept
using	O
simple	O
gzip	B-Application
,	O
because	O
the	O
SILO	B-Application
boot	B-Application
loader	I-Application
transparently	O
decompresses	O
gzipped	O
images	O
.	O
</s>
<s>
The	O
filename	O
of	O
the	O
bootable	O
image	O
is	O
not	O
important	O
,	O
but	O
many	O
popular	O
distributions	O
use	O
vmlinuz	B-Application
.	O
</s>
<s>
As	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
matured	O
,	O
the	O
size	O
of	O
the	O
kernels	B-Operating_System
generated	O
by	O
users	O
grew	O
beyond	O
the	O
limits	O
imposed	O
by	O
some	O
architectures	O
,	O
where	O
the	O
space	O
available	O
to	O
store	O
the	O
compressed	B-General_Concept
kernel	B-Operating_System
code	O
is	O
limited	O
.	O
</s>
<s>
The	O
bzImage	B-Application
(	O
big	O
zImage	B-Application
)	O
format	O
was	O
developed	O
to	O
overcome	O
this	O
limitation	O
by	O
splitting	O
the	O
kernel	B-Operating_System
over	O
non-contiguous	O
memory	B-General_Concept
regions	O
.	O
</s>
<s>
The	O
bzImage	B-Application
was	O
compressed	B-General_Concept
using	O
gzip	B-Application
until	O
Linux	O
2.6.30	O
,	O
which	O
introduced	O
more	O
algorithms	O
.	O
</s>
<s>
Although	O
the	O
bz	O
prefix	O
may	O
suggest	O
that	O
bzip2	B-Application
compression	O
is	O
used	O
,	O
this	O
is	O
not	O
the	O
case	O
.	O
</s>
<s>
(	O
The	O
bzip2	B-Application
package	O
is	O
often	O
distributed	O
with	O
tools	O
prefixed	O
with	O
bz	O
,	O
such	O
as	O
bzless	O
,	O
bzcat	O
,	O
etc	O
.	O
)	O
</s>
<s>
The	O
bzImage	B-Application
file	O
is	O
in	O
a	O
specific	O
format	O
.	O
</s>
<s>
piggy.o	O
contains	O
the	O
gzipped	O
vmlinux	B-Application
file	O
in	O
its	O
data	O
section	O
.	O
</s>
<s>
The	O
script	O
extract-vmlinux	O
found	O
under	O
scripts/	O
in	O
the	O
kernel	B-Operating_System
sources	O
decompresses	O
a	O
kernel	B-Operating_System
image	I-Operating_System
.	O
</s>
<s>
Red	O
Hat	O
and	O
clones	O
)	O
may	O
come	O
with	O
a	O
kernel-debuginfo	O
RPM	B-Application
that	O
contains	O
the	O
vmlinux	B-Application
file	O
for	O
the	O
matching	O
kernel	B-Operating_System
RPM	B-Application
,	O
and	O
it	O
typically	O
gets	O
installed	O
under	O
/usr/lib/debug/lib/modules/	O
`uname	O
-r	O
`	O
/vmlinux	O
or	O
/usr/lib/debug/lib64/modules/	O
`uname	O
-r	O
`	O
/vmlinux	O
.	O
</s>
