<s>
Docker	B-Language
is	O
a	O
set	O
of	O
platform	B-Application
as	I-Application
a	I-Application
service	I-Application
(	O
PaaS	B-Application
)	O
products	O
that	O
use	O
OS-level	B-Application
virtualization	I-Application
to	O
deliver	O
software	O
in	O
packages	O
called	O
containers	B-Application
.	O
</s>
<s>
The	O
software	O
that	O
hosts	O
the	O
containers	B-Application
is	O
called	O
Docker	B-Language
Engine	O
.	O
</s>
<s>
It	O
was	O
first	O
started	O
in	O
2013	O
and	O
is	O
developed	O
by	O
Docker	B-Language
,	O
Inc	O
.	O
</s>
<s>
Docker	B-Language
is	O
a	O
tool	O
that	O
is	O
used	O
to	O
automate	O
the	O
deployment	O
of	O
applications	O
in	O
lightweight	O
containers	B-Application
so	O
that	O
applications	O
can	O
work	O
efficiently	O
in	O
different	O
environments	O
.	O
</s>
<s>
Containers	B-Application
are	O
isolated	O
from	O
one	O
another	O
and	O
bundle	O
their	O
own	O
software	O
,	O
libraries	B-Library
and	O
configuration	O
files	O
;	O
they	O
can	O
communicate	O
with	O
each	O
other	O
through	O
well-defined	O
channels	O
.	O
</s>
<s>
Because	O
all	O
of	O
the	O
containers	B-Application
share	O
the	O
services	O
of	O
a	O
single	O
operating	B-Operating_System
system	I-Operating_System
kernel	I-Operating_System
,	O
they	O
use	O
fewer	O
resources	O
than	O
virtual	B-Architecture
machines	I-Architecture
.	O
</s>
<s>
Docker	B-Language
can	O
package	O
an	O
application	O
and	O
its	O
dependencies	O
in	O
a	O
virtual	O
container	B-Application
that	O
can	O
run	O
on	O
any	O
Linux	B-Operating_System
,	O
Windows	O
,	O
or	O
macOS	B-Application
computer	O
.	O
</s>
<s>
This	O
enables	O
the	O
application	O
to	O
run	O
in	O
a	O
variety	O
of	O
locations	O
,	O
such	O
as	O
on-premises	B-General_Concept
,	O
in	O
public	O
(	O
see	O
decentralized	B-Operating_System
computing	I-Operating_System
,	O
distributed	B-Architecture
computing	I-Architecture
,	O
and	O
cloud	B-Architecture
computing	I-Architecture
)	O
or	O
private	O
cloud	O
.	O
</s>
<s>
When	O
running	O
on	O
Linux	B-Operating_System
,	O
Docker	B-Language
uses	O
the	O
resource	O
isolation	O
features	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
(	O
such	O
as	O
cgroups	B-Application
and	O
kernel	B-Operating_System
namespaces	B-Architecture
)	O
and	O
a	O
union-capable	B-Application
file	I-Application
system	I-Application
(	O
such	O
as	O
OverlayFS	B-Application
)	O
to	O
allow	O
containers	B-Application
to	O
run	O
within	O
a	O
single	O
Linux	B-Operating_System
instance	O
,	O
avoiding	O
the	O
overhead	O
of	O
starting	O
and	O
maintaining	O
virtual	B-Architecture
machines	I-Architecture
.	O
</s>
<s>
Docker	B-Language
on	O
macOS	B-Application
uses	O
a	O
Linux	B-Operating_System
virtual	B-Architecture
machine	I-Architecture
to	O
run	O
the	O
containers	B-Application
.	O
</s>
<s>
Because	O
Docker	B-Language
containers	B-Application
are	O
lightweight	O
,	O
a	O
single	O
server	O
or	O
virtual	B-Architecture
machine	I-Architecture
can	O
run	O
several	O
containers	B-Application
simultaneously	O
.	O
</s>
<s>
A	O
2018	O
analysis	O
found	O
that	O
a	O
typical	O
Docker	B-Language
use	O
case	O
involves	O
running	O
eight	O
containers	B-Application
per	O
host	O
,	O
and	O
that	O
a	O
quarter	O
of	O
analyzed	O
organizations	O
run	O
18	O
or	O
more	O
per	O
host	O
.	O
</s>
<s>
It	O
can	O
also	O
be	O
installed	O
on	O
a	O
single	O
board	O
computer	O
like	O
the	O
Raspberry	B-Operating_System
Pi	I-Operating_System
.	O
</s>
<s>
The	O
Linux	B-Operating_System
kernel	I-Operating_System
's	O
support	O
for	O
namespaces	B-Architecture
mostly	O
isolates	O
an	O
application	O
's	O
view	O
of	O
the	O
operating	O
environment	O
,	O
including	O
process	O
trees	O
,	O
network	O
,	O
user	O
IDs	O
and	O
mounted	O
file	O
systems	O
,	O
while	O
the	O
kernel	B-Operating_System
's	O
cgroups	B-Application
provide	O
resource	O
limiting	O
for	O
memory	O
and	O
CPU	O
.	O
</s>
<s>
Since	O
version	O
0.9	O
,	O
Docker	B-Language
includes	O
its	O
own	O
component	O
(	O
called	O
""	O
)	O
to	O
use	O
virtualization	O
facilities	O
provided	O
directly	O
by	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
,	O
in	O
addition	O
to	O
using	O
abstracted	O
virtualization	O
interfaces	O
via	O
libvirt	B-Language
,	O
LXC	B-Application
and	O
systemd-nspawn	O
.	O
</s>
<s>
Docker	B-Language
implements	O
a	O
high-level	O
API	B-General_Concept
to	O
provide	O
lightweight	O
containers	B-Application
that	O
run	O
processes	O
in	O
isolation	O
.	O
</s>
<s>
The	O
Docker	B-Language
Engine	O
is	O
licensed	O
under	O
the	O
Apache	B-Application
License	I-Application
2.0	I-Application
.	O
</s>
<s>
Docker	B-Language
Desktop	O
distributes	O
some	O
components	O
that	O
are	O
licensed	O
under	O
the	O
GNU	O
General	O
Public	O
License	O
.	O
</s>
<s>
The	O
Dockerfile	B-Language
files	O
can	O
be	O
licensed	O
under	O
an	O
open-source	B-License
license	O
themselves	O
.	O
</s>
<s>
It	O
is	O
vital	O
to	O
realize	O
that	O
the	O
scope	O
of	O
this	O
license	O
statement	O
is	O
only	O
the	O
Dockerfile	B-Language
and	O
not	O
the	O
container	B-Application
image	O
.	O
</s>
<s>
The	O
Docker	B-Language
software	I-Language
as	O
a	O
service	O
offering	O
consists	O
of	O
three	O
components	O
:	O
</s>
<s>
Software	O
:	O
The	O
Docker	B-Language
daemon	B-Operating_System
,	O
called	O
dockerd	O
,	O
is	O
a	O
persistent	O
process	O
that	O
manages	O
Docker	B-Language
containers	B-Application
and	O
handles	O
container	B-Application
objects	O
.	O
</s>
<s>
The	O
daemon	B-Operating_System
listens	O
for	O
requests	O
sent	O
via	O
the	O
Docker	B-Language
Engine	O
API	B-General_Concept
.	O
</s>
<s>
The	O
Docker	B-Language
client	O
program	O
,	O
called	O
docker	B-Language
,	O
provides	O
a	O
command-line	B-Application
interface	I-Application
(	O
CLI	B-Application
)	O
,	O
that	O
allows	O
users	O
to	O
interact	O
with	O
Docker	B-Language
daemons	B-Operating_System
.	O
</s>
<s>
Objects	O
:	O
Docker	B-Language
objects	O
are	O
various	O
entities	O
used	O
to	O
assemble	O
an	O
application	O
in	O
Docker	B-Language
.	O
</s>
<s>
The	O
main	O
classes	O
of	O
Docker	B-Language
objects	O
are	O
images	O
,	O
containers	B-Application
,	O
and	O
services	O
.	O
</s>
<s>
A	O
Docker	B-Language
container	B-Application
is	O
a	O
standardized	O
,	O
encapsulated	O
environment	O
that	O
runs	O
applications	O
.	O
</s>
<s>
A	O
container	B-Application
is	O
managed	O
using	O
the	O
Docker	B-Language
API	B-General_Concept
or	O
CLI	B-Application
.	O
</s>
<s>
A	O
Docker	B-Language
image	O
is	O
a	O
read-only	O
template	O
used	O
to	O
build	O
containers	B-Application
.	O
</s>
<s>
A	O
Docker	B-Language
service	O
allows	O
containers	B-Application
to	O
be	O
scaled	O
across	O
multiple	O
Docker	B-Language
daemons	B-Operating_System
.	O
</s>
<s>
The	O
result	O
is	O
known	O
as	O
a	O
swarm	O
,	O
a	O
set	O
of	O
cooperating	O
daemons	B-Operating_System
that	O
communicate	O
through	O
the	O
Docker	B-Language
API	B-General_Concept
.	O
</s>
<s>
Registries	O
:	O
A	O
Docker	B-Language
registry	O
is	O
a	O
repository	O
for	O
Docker	B-Language
images	O
.	O
</s>
<s>
Docker	B-Language
clients	O
connect	O
to	O
registries	O
to	O
download	O
(	O
"	O
pull	O
"	O
)	O
images	O
for	O
use	O
or	O
upload	O
(	O
"	O
push	O
"	O
)	O
images	O
that	O
they	O
have	O
built	O
.	O
</s>
<s>
The	O
main	O
public	O
registry	O
is	O
Docker	B-Language
Hub	O
.	O
</s>
<s>
Docker	B-Language
Hub	O
is	O
the	O
default	O
registry	O
where	O
Docker	B-Language
looks	O
for	O
images	O
.	O
</s>
<s>
Docker	B-Language
registries	O
also	O
allow	O
the	O
creation	O
of	O
notifications	O
based	O
on	O
events	O
.	O
</s>
<s>
Docker	B-Language
Compose	O
is	O
a	O
tool	O
for	O
defining	O
and	O
running	O
multi-container	O
Docker	B-Language
applications	O
.	O
</s>
<s>
It	O
uses	O
YAML	B-Protocol
files	O
to	O
configure	O
the	O
application	O
's	O
services	O
and	O
performs	O
the	O
creation	O
and	O
start-up	O
process	O
of	O
all	O
the	O
containers	B-Application
with	O
a	O
single	O
command	O
.	O
</s>
<s>
The	O
docker-compose	O
CLI	B-Application
utility	O
allows	O
users	O
to	O
run	O
commands	O
on	O
multiple	O
containers	B-Application
at	O
once	O
,	O
for	O
example	O
,	O
building	O
images	O
,	O
scaling	B-Architecture
containers	B-Application
,	O
running	O
containers	B-Application
that	O
were	O
stopped	O
,	O
and	O
more	O
.	O
</s>
<s>
Commands	O
related	O
to	O
image	O
manipulation	O
,	O
or	O
user-interactive	O
options	O
,	O
are	O
not	O
relevant	O
in	O
Docker	B-Language
Compose	O
because	O
they	O
address	O
one	O
container	B-Application
.	O
</s>
<s>
The	O
docker-compose.yml	O
file	O
is	O
used	O
to	O
define	O
an	O
application	O
's	O
services	O
and	O
includes	O
various	O
configuration	O
options	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
build	O
option	O
defines	O
configuration	O
options	O
such	O
as	O
the	O
Dockerfile	B-Language
path	O
,	O
the	O
command	O
option	O
allows	O
one	O
to	O
override	O
default	O
Docker	B-Language
commands	O
,	O
and	O
more	O
.	O
</s>
<s>
The	O
first	O
public	O
beta	O
version	O
of	O
Docker	B-Language
Compose	O
(	O
version	O
0.0.1	O
)	O
was	O
released	O
on	O
December	O
21	O
,	O
2013	O
.	O
</s>
<s>
Docker	B-Language
Swarm	O
provides	O
native	O
clustering	B-Architecture
functionality	O
for	O
Docker	B-Language
containers	B-Application
,	O
which	O
turns	O
a	O
group	O
of	O
Docker	B-Language
engines	O
into	O
a	O
single	O
virtual	O
Docker	B-Language
engine	O
.	O
</s>
<s>
In	O
Docker	B-Language
1.12	O
and	O
higher	O
,	O
Swarm	O
mode	O
is	O
integrated	O
with	O
Docker	B-Language
Engine	O
.	O
</s>
<s>
The	O
docker	B-Language
swarm	O
CLI	B-Application
utility	O
allows	O
users	O
to	O
run	O
Swarm	O
containers	B-Application
,	O
create	O
discovery	O
tokens	O
,	O
list	O
nodes	O
in	O
the	O
cluster	O
,	O
and	O
more	O
.	O
</s>
<s>
The	O
docker	B-Language
node	O
CLI	B-Application
utility	O
allows	O
users	O
to	O
run	O
various	O
commands	O
to	O
manage	O
nodes	O
in	O
a	O
swarm	O
,	O
for	O
example	O
,	O
listing	O
the	O
nodes	O
in	O
a	O
swarm	O
,	O
updating	O
nodes	O
,	O
and	O
removing	O
nodes	O
from	O
the	O
swarm	O
.	O
</s>
<s>
Docker	B-Language
manages	O
swarms	O
using	O
the	O
Raft	B-Operating_System
consensus	I-Operating_System
algorithm	I-Operating_System
.	O
</s>
<s>
According	O
to	O
Raft	B-Operating_System
,	O
for	O
an	O
update	O
to	O
be	O
performed	O
,	O
the	O
majority	O
of	O
Swarm	O
nodes	O
need	O
to	O
agree	O
on	O
the	O
update	O
.	O
</s>
<s>
Docker	B-Language
Volume	O
facilitates	O
the	O
independent	O
persistence	O
of	O
data	O
,	O
allowing	O
data	O
to	O
remain	O
even	O
after	O
the	O
container	B-Application
is	O
deleted	O
or	O
re-created	O
.	O
</s>
<s>
Docker	B-Language
Inc	O
.	O
was	O
founded	O
by	O
Kamel	O
Founadi	O
,	O
Solomon	O
Hykes	O
,	O
and	O
Sebastien	O
Pahl	O
during	O
the	O
Y	O
Combinator	O
Summer	O
2010	O
startup	O
incubator	O
group	O
and	O
launched	O
in	O
2011	O
.	O
</s>
<s>
Hykes	O
started	O
the	O
Docker	B-Language
project	O
in	O
France	O
as	O
an	O
internal	O
project	O
within	O
dotCloud	O
,	O
a	O
platform-as-a-service	B-Application
company	O
.	O
</s>
<s>
Docker	B-Language
debuted	O
to	O
the	O
public	O
in	O
Santa	O
Clara	O
at	O
PyCon	B-Language
in	O
2013	O
.	O
</s>
<s>
It	O
was	O
released	O
as	O
open-source	B-License
in	O
March	O
2013	O
.	O
</s>
<s>
At	O
the	O
time	O
,	O
it	O
used	O
LXC	B-Application
as	O
its	O
default	O
execution	O
environment	O
.	O
</s>
<s>
One	O
year	O
later	O
,	O
with	O
the	O
release	O
of	O
version	O
0.9	O
,	O
Docker	B-Language
replaced	O
LXC	B-Application
with	O
its	O
own	O
component	O
,	O
libcontainer	B-Language
,	O
which	O
was	O
written	O
in	O
the	O
Go	B-Application
programming	I-Application
language	I-Application
.	O
</s>
<s>
In	O
2017	O
,	O
Docker	B-Language
created	O
the	O
Moby	O
project	O
for	O
open	O
research	O
and	O
development	O
.	O
</s>
<s>
September	O
19	O
,	O
2013	O
:	O
Red	O
Hat	O
and	O
Docker	B-Language
announced	O
a	O
collaboration	O
around	O
Fedora	O
,	O
Red	O
Hat	O
Enterprise	O
Linux	B-Operating_System
(	O
RHEL	O
)	O
,	O
and	O
OpenShift	B-General_Concept
.	O
</s>
<s>
October	O
15	O
,	O
2014	O
:	O
Microsoft	O
announced	O
the	O
integration	O
of	O
the	O
Docker	B-Language
engine	O
into	O
Windows	B-Device
Server	I-Device
,	O
as	O
well	O
as	O
native	O
support	O
for	O
the	O
Docker	B-Language
client	O
role	O
in	O
Windows	O
.	O
</s>
<s>
November	O
2014	O
:	O
Docker	B-Language
container	B-Application
services	I-Application
were	O
announced	O
for	O
the	O
Amazon	B-General_Concept
Elastic	I-General_Concept
Compute	I-General_Concept
Cloud	I-General_Concept
(	O
EC2	O
)	O
.	O
</s>
<s>
November	O
10	O
,	O
2014	O
:	O
Docker	B-Language
announced	O
a	O
partnership	O
with	O
Stratoscale	B-General_Concept
.	O
</s>
<s>
December	O
4	O
,	O
2014	O
:	O
IBM	O
announced	O
a	O
strategic	O
partnership	O
with	O
Docker	B-Language
that	O
enables	O
Docker	B-Language
to	O
integrate	O
more	O
closely	O
with	O
the	O
IBM	O
Cloud	O
.	O
</s>
<s>
June	O
22	O
,	O
2015	O
:	O
Docker	B-Language
and	O
several	O
other	O
companies	O
announced	O
that	O
they	O
are	O
working	O
on	O
a	O
new	O
vendor	O
and	O
operating-system-independent	O
standard	O
for	O
software	B-Application
containers	I-Application
.	O
</s>
<s>
December	O
2015	O
:	O
Oracle	B-General_Concept
Cloud	I-General_Concept
added	O
Docker	B-Language
container	B-Application
support	O
after	O
acquiring	O
StackEngine	O
,	O
a	O
Docker	B-Language
container	B-Application
startup	O
.	O
</s>
<s>
April	O
2016	O
:	O
Windocks	O
,	O
an	O
independent	B-Application
software	I-Application
vendor	I-Application
released	O
a	O
port	O
of	O
Docker	B-Language
's	O
open	B-License
source	I-License
project	O
to	O
Windows	O
,	O
supporting	O
Windows	B-Device
Server	I-Device
2012	O
R2	O
and	O
Server	O
2016	O
,	O
with	O
all	O
editions	O
of	O
SQL	O
Server	O
2008	O
onward	O
.	O
</s>
<s>
May	O
2016	O
:	O
analysis	O
showed	O
the	O
following	O
organizations	O
as	O
main	O
contributors	O
to	O
Docker	B-Language
:	O
The	O
Docker	B-Language
team	O
,	O
Cisco	O
,	O
Google	B-Application
,	O
Huawei	O
,	O
IBM	O
,	O
Microsoft	O
,	O
and	O
Red	O
Hat	O
.	O
</s>
<s>
June	O
8	O
,	O
2016	O
:	O
Microsoft	O
announced	O
that	O
Docker	B-Language
could	O
now	O
be	O
used	O
natively	O
on	O
Windows	B-Operating_System
10	I-Operating_System
.	O
</s>
<s>
January	O
2017	O
:	O
An	O
analysis	O
of	O
LinkedIn	B-Application
profile	O
mentions	O
showed	O
Docker	B-Language
presence	O
grew	O
by	O
160%	O
in	O
2016	O
.	O
</s>
<s>
May	O
6	O
,	O
2019	O
:	O
Microsoft	O
announced	O
the	O
second	O
version	O
of	O
Windows	O
Subsystem	O
for	O
Linux	B-Operating_System
(	O
WSL	O
)	O
.	O
</s>
<s>
Docker	B-Language
,	O
Inc	O
.	O
announced	O
that	O
it	O
has	O
started	O
working	O
on	O
a	O
version	O
of	O
Docker	B-Language
for	O
Windows	O
that	O
runs	O
on	O
WSL	O
2	O
.	O
</s>
<s>
In	O
particular	O
,	O
this	O
means	O
Docker	B-Language
can	O
run	O
on	O
Windows	B-Operating_System
10	I-Operating_System
Home	O
(	O
previously	O
it	O
was	O
limited	O
to	O
Windows	O
Pro	O
and	O
Enterprise	O
since	O
it	O
used	O
Hyper-V	O
)	O
.	O
</s>
<s>
August	O
2020	O
:	O
Microsoft	O
announced	O
a	O
backport	O
of	O
WSL2	O
to	O
Windows	B-Operating_System
10	I-Operating_System
versions	O
1903	O
and	O
1909	O
(	O
previously	O
WSL2	O
was	O
available	O
only	O
on	O
version	O
2004	O
)	O
and	O
Docker	B-Language
developers	O
announced	O
availability	O
of	O
Docker	B-Language
for	O
these	O
platforms	O
.	O
</s>
<s>
August	O
2021	O
:	O
Docker	B-Language
Desktop	O
for	O
Windows	O
and	O
MacOS	B-Application
is	O
no	O
longer	O
free	O
for	O
enterprise	O
users	O
.	O
</s>
<s>
Docker	B-Language
ended	O
free	O
Docker	B-Language
Desktop	O
use	O
for	O
larger	O
business	O
customers	O
and	O
replaced	O
its	O
Free	O
plan	O
with	O
a	O
Personal	O
plan	O
.	O
</s>
<s>
Docker	B-Language
on	O
Linux	B-Operating_System
distributions	O
remains	O
unaffected	O
.	O
</s>
