<s>
An	O
Amazon	B-Application
Machine	I-Application
Image	I-Application
(	O
AMI	O
)	O
is	O
a	O
special	O
type	O
of	O
virtual	B-Application
appliance	I-Application
that	O
is	O
used	O
to	O
create	O
a	O
virtual	B-Architecture
machine	I-Architecture
within	O
the	O
Amazon	B-General_Concept
Elastic	I-General_Concept
Compute	I-General_Concept
Cloud	I-General_Concept
(	O
"	O
EC2	O
"	O
)	O
.	O
</s>
<s>
Like	O
all	O
virtual	B-Application
appliances	I-Application
,	O
the	O
main	O
component	O
of	O
an	O
AMI	O
is	O
a	O
read-only	O
filesystem	O
image	O
that	O
includes	O
an	O
operating	B-General_Concept
system	I-General_Concept
(	O
e.g.	O
,	O
Linux	B-Operating_System
,	O
Unix	B-Application
,	O
or	O
Windows	O
)	O
and	O
any	O
additional	O
software	O
required	O
to	O
deliver	O
a	O
service	O
or	O
a	O
portion	O
of	O
it	O
.	O
</s>
<s>
The	O
AMI	O
filesystem	O
is	O
compressed	O
,	O
encrypted	O
,	O
signed	O
,	O
split	O
into	O
a	O
series	O
of	O
10MB	O
chunks	O
and	O
uploaded	O
into	O
Amazon	B-General_Concept
S3	I-General_Concept
for	O
storage	O
.	O
</s>
<s>
An	O
XML	O
manifest	O
file	O
stores	O
information	O
about	O
the	O
AMI	O
,	O
including	O
name	O
,	O
version	O
,	O
architecture	O
,	O
default	O
kernel	B-Operating_System
id	O
,	O
decryption	O
key	O
and	O
digests	O
for	O
all	O
of	O
the	O
filesystem	O
chunks	O
.	O
</s>
<s>
Current	O
AMIs	O
are	O
available	O
for	O
hardware	B-General_Concept
virtualized	I-General_Concept
machines	I-General_Concept
(	O
HVM	O
)	O
where	O
the	O
operating	B-General_Concept
system	I-General_Concept
is	O
installed	O
as	O
it	O
would	O
be	O
on	O
real	O
hardware	O
.	O
</s>
<s>
With	O
the	O
still	O
available	O
older	O
paravirtualized	O
virtual	B-Architecture
machines	I-Architecture
(	O
PV	O
)	O
,	O
an	O
AMI	O
did	O
not	O
include	O
a	O
kernel	B-Operating_System
image	O
,	O
only	O
a	O
pointer	O
to	O
the	O
default	O
kernel	B-Operating_System
id	O
,	O
which	O
could	O
be	O
chosen	O
from	O
an	O
approved	O
list	O
of	O
safe	O
kernels	B-Operating_System
maintained	O
by	O
Amazon	O
and	O
its	O
partners	O
(	O
e.g.	O
,	O
Red	O
Hat	O
,	O
Canonical	O
,	O
Microsoft	O
)	O
.	O
</s>
<s>
Users	O
could	O
choose	O
kernels	B-Operating_System
other	O
than	O
the	O
default	O
when	O
booting	O
an	O
PVM	O
AMI	O
.	O
</s>
<s>
When	O
it	O
launched	O
in	O
August	O
2006	O
,	O
the	O
EC2	O
service	O
offered	O
Linux	B-Operating_System
and	O
later	O
Sun	O
Microsystems	O
 '	O
OpenSolaris	B-Operating_System
and	O
Solaris	B-Application
Express	I-Application
Community	I-Application
Edition	I-Application
.	O
</s>
<s>
In	O
October	O
2008	O
,	O
EC2	O
added	O
the	O
Windows	B-Application
Server	I-Application
2003	I-Application
and	O
Windows	B-Device
Server	I-Device
2008	I-Device
operating	B-General_Concept
systems	I-General_Concept
to	O
the	O
list	O
of	O
available	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
As	O
of	O
December	O
2010	O
,	O
it	O
has	O
also	O
been	O
reported	O
to	O
run	O
FreeBSD	B-Operating_System
;	O
in	O
March	O
2011	O
,	O
NetBSD	B-Device
AMIs	O
became	O
available	O
.	O
</s>
<s>
In	O
November	O
2012	O
,	O
Windows	B-Device
Server	I-Device
2012	I-Device
support	O
was	O
added	O
.	O
</s>
<s>
Amazon	O
has	O
its	O
own	O
Linux	B-Operating_System
distribution	O
that	O
is	O
largely	O
binary	O
compatible	O
with	O
Red	O
Hat	O
Enterprise	O
Linux	B-Operating_System
.	O
</s>
<s>
The	O
final	O
release	O
of	O
the	O
original	O
Amazon	O
Linux	B-Operating_System
is	O
version	O
2018.03	O
and	O
uses	O
version	O
4.14	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
Amazon	O
Linux	B-Operating_System
2	O
changed	O
from	O
System	O
V	O
init	O
system	O
to	O
systemd	B-Application
boot	O
.	O
</s>
<s>
Shared	O
:	O
a	O
private	O
AMI	O
that	O
can	O
only	O
be	O
used	O
by	O
Amazon	B-General_Concept
EC2	I-General_Concept
users	O
who	O
are	O
allowed	O
access	O
to	O
it	O
by	O
the	O
developer	O
.	O
</s>
