1
00:00:00,000 --> 00:00:04,300
[Intro Music]

2
00:00:04,380 --> 00:00:06,330
We have just successfully pulled

3
00:00:06,360 --> 00:00:07,830
two different images from Docker

4
00:00:07,830 --> 00:00:09,690
Hub. And those images are

5
00:00:09,720 --> 00:00:11,940
hello-world and busybox. And

6
00:00:11,940 --> 00:00:13,140
basically now we are ready to

7
00:00:13,140 --> 00:00:15,180
create new containers from those

8
00:00:15,210 --> 00:00:17,730
images. But before doing that, let

9
00:00:17,730 --> 00:00:19,320
me explain you the structure of

10
00:00:19,320 --> 00:00:21,180
every image, and explain you

11
00:00:21,240 --> 00:00:23,460
actually key points about images.

12
00:00:24,450 --> 00:00:26,460
In a nutshell, every image is

13
00:00:26,490 --> 00:00:29,010
simply a set of files, that's that

14
00:00:29,010 --> 00:00:31,740
simple. And when you pull image

15
00:00:31,740 --> 00:00:33,810
from Remote Registry like Docker

16
00:00:33,810 --> 00:00:36,450
Hub, you download simply a set of

17
00:00:36,450 --> 00:00:38,730
files and folders, that's that simple.

18
00:00:39,930 --> 00:00:41,880
But every image is actually

19
00:00:41,880 --> 00:00:44,580
splitted into different file system

20
00:00:44,580 --> 00:00:48,630
layers, or shortly 'fs' layers. And

21
00:00:48,630 --> 00:00:50,250
you may ask me, what is the reason

22
00:00:50,280 --> 00:00:52,050
for splitting the images into

23
00:00:52,050 --> 00:00:55,470
multiple 'fs' layers? Answer is very

24
00:00:55,470 --> 00:00:57,990
simple, using such splitting

25
00:00:57,990 --> 00:01:01,080
approach, we are able to reuse

26
00:01:01,110 --> 00:01:03,000
different 'fs' layers in

27
00:01:03,030 --> 00:01:06,060
different images. For example,

28
00:01:06,209 --> 00:01:07,980
let's say that there is an image

29
00:01:08,010 --> 00:01:11,790
that has PHP installed in it. And

30
00:01:11,790 --> 00:01:13,890
now you want to create image that

31
00:01:13,890 --> 00:01:16,440
will be running WordPress. You

32
00:01:16,440 --> 00:01:18,330
probably know that WordPress uses

33
00:01:18,330 --> 00:01:21,210
PHP. And if you create wordpress

34
00:01:21,240 --> 00:01:24,810
image, you could reuse 'fs' layers in

35
00:01:24,810 --> 00:01:27,960
the 'php' image, and add additional

36
00:01:27,960 --> 00:01:30,390
layers that will install WordPress

37
00:01:30,390 --> 00:01:33,300
and run it afterwards. That's

38
00:01:33,330 --> 00:01:35,100
reusability of different 'fs'

39
00:01:35,100 --> 00:01:38,370
layers. Also, every image has so

40
00:01:38,370 --> 00:01:41,610
called Base Image. For example,

41
00:01:41,640 --> 00:01:44,190
Base Image could be busybox, or

42
00:01:44,190 --> 00:01:46,470
alpine, or ubuntu, or something

43
00:01:46,470 --> 00:01:49,842
else. And on top of that Base Image

44
00:01:49,842 --> 00:01:51,300
you are able to add

45
00:01:51,330 --> 00:01:52,950
additional layers like in this

46
00:01:52,950 --> 00:01:55,530
example, Layer 1, then on top of

47
00:01:55,530 --> 00:01:57,210
Layer 1 you add additional Layer

48
00:01:57,240 --> 00:01:59,040
2 image, and next you add

49
00:01:59,070 --> 00:02:01,620
additional Layer 3 image. And

50
00:02:01,620 --> 00:02:03,630
different images may have different

51
00:02:03,630 --> 00:02:06,540
quantity of the 'fs' layers. Some

52
00:02:06,570 --> 00:02:08,940
simple images may have just one or

53
00:02:08,940 --> 00:02:11,460
two 'fs' layers, more complicated

54
00:02:11,490 --> 00:02:13,380
images may have 10s of different

55
00:02:13,380 --> 00:02:16,140
layers. Alright, let me now talk

56
00:02:16,140 --> 00:02:18,150
about key points about Docker

57
00:02:18,150 --> 00:02:21,030
Image. First of all Docker Image is

58
00:02:21,060 --> 00:02:23,850
read-only. You are not able to

59
00:02:23,880 --> 00:02:26,430
modify existing Docker Image. It is

60
00:02:26,430 --> 00:02:29,040
not possible at all. But you are

61
00:02:29,040 --> 00:02:31,920
able to create custom image based

62
00:02:31,950 --> 00:02:35,850
on other image if you want. And if

63
00:02:35,880 --> 00:02:37,440
we'll get back to images that we

64
00:02:37,440 --> 00:02:39,060
have already pulled from Docker Hub

65
00:02:39,060 --> 00:02:41,070
hello-world and busybox, you are

66
00:02:41,070 --> 00:02:42,990
not able to modify those images.

67
00:02:43,710 --> 00:02:45,150
You are able just to create

68
00:02:45,150 --> 00:02:47,280
containers based on those images,

69
00:02:47,460 --> 00:02:49,590
or create other images based on

70
00:02:49,590 --> 00:02:52,590
those images. Next, as I have

71
00:02:52,590 --> 00:02:54,330
already told you every image

72
00:02:54,360 --> 00:02:56,760
consists of multiple file system

73
00:02:56,760 --> 00:03:00,930
layers. And there could be 1, 2, 3, 10s,

74
00:03:00,960 --> 00:03:02,880
100s of different 'fs' layers,

75
00:03:03,120 --> 00:03:05,670
as much as you want. Next, images

76
00:03:05,670 --> 00:03:07,470
could be stored in a private or

77
00:03:07,470 --> 00:03:10,020
public repositories. And we have

78
00:03:10,020 --> 00:03:11,730
actually used the public

79
00:03:11,730 --> 00:03:14,100
repositories for hello-world and

80
00:03:14,130 --> 00:03:15,960
busybox images. And those

81
00:03:15,960 --> 00:03:17,730
repositories are available at

82
00:03:17,760 --> 00:03:20,970
Docker Hub Public Registry. But

83
00:03:20,970 --> 00:03:23,100
you're also able to create private

84
00:03:23,100 --> 00:03:25,530
repositories if you create some

85
00:03:25,530 --> 00:03:27,780
proprietary images, and that your

86
00:03:27,780 --> 00:03:31,080
company only uses. Next, images could

87
00:03:31,080 --> 00:03:34,260
be copied, deleted or moved. And

88
00:03:34,260 --> 00:03:35,730
actually in the previous lecture,

89
00:03:35,820 --> 00:03:38,610
we have simply copied images from a

90
00:03:38,610 --> 00:03:40,650
remote server to our local

91
00:03:40,650 --> 00:03:42,930
computer. And in the same way,

92
00:03:42,990 --> 00:03:45,150
you're able to copy images from

93
00:03:45,150 --> 00:03:46,890
your computer and move it to other

94
00:03:46,890 --> 00:03:48,570
computer if you want to. Because

95
00:03:48,570 --> 00:03:50,760
every image again is simply a set

96
00:03:50,760 --> 00:03:53,490
of files. But during download

97
00:03:53,490 --> 00:03:55,530
process, you may have noticed that

98
00:03:55,650 --> 00:03:58,440
we were pulling different 'fs' layers.

99
00:03:59,070 --> 00:04:01,380
And actually when you pull image

100
00:04:01,380 --> 00:04:03,030
from a remote repository, from

101
00:04:03,030 --> 00:04:04,980
Remote Registry, then you are

102
00:04:04,980 --> 00:04:08,220
pulling archived 'fs' layers. And if

103
00:04:08,220 --> 00:04:10,140
for example, image has three

104
00:04:10,140 --> 00:04:11,850
different 'fs' layers, then you'll

105
00:04:11,850 --> 00:04:13,980
download three different archives.

106
00:04:14,490 --> 00:04:16,589
It is done for optimization of

107
00:04:16,589 --> 00:04:19,079
bandwidth usage. And afterwards on

108
00:04:19,079 --> 00:04:20,970
your local computer Docker will

109
00:04:21,000 --> 00:04:22,860
extract contents from those

110
00:04:22,860 --> 00:04:26,040
archives. Alright, next, you're

111
00:04:26,070 --> 00:04:28,530
able to use official or community

112
00:04:28,560 --> 00:04:30,870
images. And in the previous lecture

113
00:04:30,900 --> 00:04:33,480
hello-world and busybox images were

114
00:04:33,540 --> 00:04:36,480
official images. And if I go back

115
00:04:36,510 --> 00:04:38,490
to Docker Hub, here you will see

116
00:04:38,490 --> 00:04:40,770
that hello-world is Docker Official

117
00:04:40,770 --> 00:04:42,780
Image. But if I'll type for

118
00:04:42,780 --> 00:04:44,040
example, let's say,

119
00:04:44,910 --> 00:04:49,200
'php', you'll see that there is also

120
00:04:49,200 --> 00:04:52,140
php Official Image available; but

121
00:04:52,170 --> 00:04:55,110
if I scroll a bit down, you'll see

122
00:04:55,110 --> 00:04:57,750
such images as 'phpmyadmin/

123
00:04:57,750 --> 00:05:01,590
phpmyadmin', 'phpdockerio/

124
00:05:01,590 --> 00:05:05,850
php73-fpm'; and those images are

125
00:05:05,850 --> 00:05:08,100
community images. They were created

126
00:05:08,100 --> 00:05:11,010
by specific users. This image

127
00:05:11,040 --> 00:05:13,680
was created by 'phpmyadmin' user,

128
00:05:13,830 --> 00:05:16,890
this by 'phpdockerio' user, and so

129
00:05:16,890 --> 00:05:19,050
on. Again, there are official

130
00:05:19,050 --> 00:05:22,170
images and community images. You're of

131
00:05:22,170 --> 00:05:24,030
course able to use either

132
00:05:24,030 --> 00:05:26,220
official images or community images

133
00:05:26,340 --> 00:05:28,410
as long as they are publicly

134
00:05:28,410 --> 00:05:31,470
available. Alright, that's what I

135
00:05:31,470 --> 00:05:33,060
wanted to tell you about Docker

136
00:05:33,090 --> 00:05:35,640
Images. And the key point here is

137
00:05:35,640 --> 00:05:38,010
that every image is read-only, you

138
00:05:38,010 --> 00:05:39,810
are not able to modify the image.

139
00:05:40,320 --> 00:05:42,000
And the second key point is that

140
00:05:42,000 --> 00:05:44,400
every image consists of multiple

141
00:05:44,430 --> 00:05:47,400
file system layers. And every file

142
00:05:47,400 --> 00:05:49,380
system layer is simply a set of

143
00:05:49,380 --> 00:05:52,830
files and folders. Alright, that's

144
00:05:52,830 --> 00:05:55,110
all for image structure overview.

145
00:05:55,320 --> 00:05:57,420
And next, let's proceed and let's

146
00:05:57,420 --> 00:05:59,850
try to create first container based

147
00:05:59,880 --> 00:06:02,040
on hello-world image. I'll see you

148
00:06:02,040 --> 00:06:03,558
in the next lecture guys. Bye-Bye.

149
00:06:03,558 --> 00:06:05,994
[no audio]