1
00:00:06,450 --> 00:00:07,283
- All right.

2
00:00:07,283 --> 00:00:09,330
So we need man in related to resources,

3
00:00:09,330 --> 00:00:12,510
to find out how to change the
hostname of your computer.

4
00:00:12,510 --> 00:00:16,083
Well, I would say let's start with man,

5
00:00:18,180 --> 00:00:20,163
man -k hostname,

6
00:00:21,750 --> 00:00:26,730
which is bringing me a
reasonable amount of commands.

7
00:00:26,730 --> 00:00:29,310
That is all almost too easy.

8
00:00:29,310 --> 00:00:33,240
And I can see there's hostname
and there's hostnamectl.

9
00:00:33,240 --> 00:00:36,150
hostnamectl, control the system hostname.

10
00:00:36,150 --> 00:00:37,500
That's the one that we need.

11
00:00:37,500 --> 00:00:38,760
So how do we use that?

12
00:00:38,760 --> 00:00:42,540
Well, let's use man on hostnamectl.

13
00:00:42,540 --> 00:00:46,563
And there we get the description
of the hostnamectl command.

14
00:00:47,580 --> 00:00:51,000
So does it have any help?

15
00:00:51,000 --> 00:00:52,500
It doesn't have any help?

16
00:00:52,500 --> 00:00:53,940
And if it doesn't have any help

17
00:00:53,940 --> 00:00:56,250
that means that it should be possible

18
00:00:56,250 --> 00:01:01,250
to figure this out in a
real easy way for yourself.

19
00:01:01,290 --> 00:01:02,123
And as you can see,

20
00:01:02,123 --> 00:01:05,070
there are options and there
is, well, you know what?

21
00:01:05,070 --> 00:01:07,380
I don't feel like reading all of this.

22
00:01:07,380 --> 00:01:12,180
Let's use hostnamectl --help
for the quick overview.

23
00:01:12,180 --> 00:01:13,140
Now this is cool.

24
00:01:13,140 --> 00:01:14,400
This is what I need.

25
00:01:14,400 --> 00:01:17,970
And I can see that we have
a hostnamectl hostname,

26
00:01:17,970 --> 00:01:22,260
which can be used to
get set hostname status.

27
00:01:22,260 --> 00:01:27,030
So, hostnamectl hostname centos

28
00:01:27,030 --> 00:01:30,990
will set the hostname
for my current system.

29
00:01:30,990 --> 00:01:33,750
It'll set it for something
that it already was.

30
00:01:33,750 --> 00:01:34,583
Does that matter?

31
00:01:34,583 --> 00:01:35,970
No, not really.

32
00:01:35,970 --> 00:01:37,230
What matters is that, you know

33
00:01:37,230 --> 00:01:40,650
that this is how you use hostnamectl.

34
00:01:40,650 --> 00:01:44,130
Then we have the second part of the lab.

35
00:01:44,130 --> 00:01:46,140
Read the help output for ip,

36
00:01:46,140 --> 00:01:48,960
and find how you can bring down a link.

37
00:01:48,960 --> 00:01:53,960
ip --help, is that going
to be something useful?

38
00:01:54,240 --> 00:01:57,210
Well, at least it is
showing what we can do.

39
00:01:57,210 --> 00:01:58,950
And this is voted number one

40
00:01:58,950 --> 00:02:02,190
most user unfriendly help output.

41
00:02:02,190 --> 00:02:04,380
So let's study, how does this work?

42
00:02:04,380 --> 00:02:05,880
ip OBJECT.

43
00:02:05,880 --> 00:02:07,080
So we have an OBJECT

44
00:02:07,080 --> 00:02:09,690
and the objects are specified right here,

45
00:02:09,690 --> 00:02:11,790
and these are all the objects.

46
00:02:11,790 --> 00:02:14,010
So I need to do something with a link.

47
00:02:14,010 --> 00:02:16,320
Now, look at that, we have ip link.

48
00:02:16,320 --> 00:02:21,090
And then we have a
command behind the OBJECT,

49
00:02:21,090 --> 00:02:23,730
well, I don't know which command to work

50
00:02:23,730 --> 00:02:27,510
but ip link --help.

51
00:02:27,510 --> 00:02:30,720
Is it going to bring us any further?

52
00:02:30,720 --> 00:02:32,520
Well, in a certain way it does,

53
00:02:32,520 --> 00:02:35,970
because it's telling me --help is unknown.

54
00:02:35,970 --> 00:02:37,740
Type ip link help.

55
00:02:37,740 --> 00:02:40,200
Okay, let's type ip link help.

56
00:02:40,200 --> 00:02:41,220
And there we go.

57
00:02:41,220 --> 00:02:43,590
And oh boy, oh boy, oh boy.

58
00:02:43,590 --> 00:02:46,740
That is a lot of information.

59
00:02:46,740 --> 00:02:48,750
So let's scroll up a little bit

60
00:02:48,750 --> 00:02:53,130
where we can find ip
link set DEVICE up down.

61
00:02:53,130 --> 00:02:55,380
Hey, ip link set DEVICE up down.

62
00:02:55,380 --> 00:02:56,213
Well, what is DEVICE?

63
00:02:56,213 --> 00:02:58,800
DEVICE is your network device.

64
00:02:58,800 --> 00:03:02,370
ip a, as we have seen before, is ens33.

65
00:03:02,370 --> 00:03:06,210
So ens33 is my network device.

66
00:03:06,210 --> 00:03:11,210
ip link down ens33, something like that.

67
00:03:13,170 --> 00:03:14,280
And oh, no.

68
00:03:14,280 --> 00:03:17,553
Command down is unknown.

69
00:03:18,600 --> 00:03:21,510
Command down is unknown?

70
00:03:21,510 --> 00:03:23,220
Did we overlook something?

71
00:03:23,220 --> 00:03:27,030
Well, let's do another ip link help,

72
00:03:27,030 --> 00:03:30,720
and scroll up because for some reason,

73
00:03:30,720 --> 00:03:32,580
the pipe doesn't work here.

74
00:03:32,580 --> 00:03:34,560
And ah, there, I see, I miss it.

75
00:03:34,560 --> 00:03:36,660
ip link set is the command.

76
00:03:36,660 --> 00:03:40,500
So we need ip link set ens33 down.

77
00:03:40,500 --> 00:03:41,880
Let me try again.

78
00:03:41,880 --> 00:03:46,323
ip link set ens33 down.

79
00:03:47,400 --> 00:03:50,370
Uh-oh, operation not permitted.

80
00:03:50,370 --> 00:03:51,360
Do you have anything?

81
00:03:51,360 --> 00:03:52,530
What is going on?

82
00:03:52,530 --> 00:03:53,880
Of course you do.

83
00:03:53,880 --> 00:03:57,120
This requires sudo superpowers.

84
00:03:57,120 --> 00:04:00,390
So let's learn the command
again with sudo in front of it.

85
00:04:00,390 --> 00:04:02,880
It's prompting for my sudo password.

86
00:04:02,880 --> 00:04:04,020
And there we go.

87
00:04:04,020 --> 00:04:06,750
At this point, the link is down.

88
00:04:06,750 --> 00:04:10,530
And if I type ip a again,

89
00:04:10,530 --> 00:04:13,984
then right here in the state,
we can see that it is down.

90
00:04:13,984 --> 00:04:16,050
Can we bring it up again?

91
00:04:16,050 --> 00:04:18,420
Well, if you remember
the output of the help,

92
00:04:18,420 --> 00:04:22,710
there is also ip link set whatever up

93
00:04:22,710 --> 00:04:24,900
to bring the link up again.

94
00:04:24,900 --> 00:04:27,300
And ip a is our final command.

95
00:04:27,300 --> 00:04:28,860
Uh-oh, this is a typo.

96
00:04:28,860 --> 00:04:30,150
And I did this on accident

97
00:04:30,150 --> 00:04:32,250
but it's useful to see this typo.

98
00:04:32,250 --> 00:04:34,890
I used ip a with the back slash behind it.

99
00:04:34,890 --> 00:04:37,890
The back slash means that the Linux shell

100
00:04:37,890 --> 00:04:40,590
expects us to continue on the next line.

101
00:04:40,590 --> 00:04:43,470
So it's opening what we
call a secondary prompt.

102
00:04:43,470 --> 00:04:46,530
This > is our secondary prompt,

103
00:04:46,530 --> 00:04:47,760
but I don't wanna be here.

104
00:04:47,760 --> 00:04:49,200
So how do I get out?

105
00:04:49,200 --> 00:04:51,960
Well, CTRL + C is always a good guess.

106
00:04:51,960 --> 00:04:54,150
I'm using CTRL + C to interrupt,

107
00:04:54,150 --> 00:04:58,080
and now I can repeat the command
by pressing the Up Arrow,

108
00:04:58,080 --> 00:05:01,170
and we can see that the link is up again.

109
00:05:01,170 --> 00:05:03,480
And that means that we are good.

110
00:05:03,480 --> 00:05:06,240
And that's all that you
needed to do for this lab.

111
00:05:06,240 --> 00:05:08,103
Let's continue with the next lesson.