1 00:00:00,050 --> 00:00:00,930 In this lesson, 2 00:00:00,930 --> 00:00:03,270 we're going to talk about how you can connect a Linux system 3 00:00:03,270 --> 00:00:05,400 to a home or office network. 4 00:00:05,400 --> 00:00:06,450 Now, computers are connected 5 00:00:06,450 --> 00:00:09,030 to a network to exchange information or resources 6 00:00:09,030 --> 00:00:10,260 to each other. 7 00:00:10,260 --> 00:00:11,760 Two or more computers that are connected 8 00:00:11,760 --> 00:00:14,550 through network media are called a computer network 9 00:00:14,550 --> 00:00:17,310 and there are a number of different network devices or media 10 00:00:17,310 --> 00:00:19,920 that are going to be involved to form a computer network. 11 00:00:19,920 --> 00:00:22,200 A computer that's loaded with the Linux operating system 12 00:00:22,200 --> 00:00:23,790 can also be part of a network, 13 00:00:23,790 --> 00:00:25,830 whether it's a small or large network 14 00:00:25,830 --> 00:00:28,440 by using multitasking and multi-user natures 15 00:00:28,440 --> 00:00:30,300 of the Linux operating system. 16 00:00:30,300 --> 00:00:33,060 It's your job as a system or network administrator 17 00:00:33,060 --> 00:00:34,770 to maintain your system and network 18 00:00:34,770 --> 00:00:36,930 and ensure it's up and running at all times. 19 00:00:36,930 --> 00:00:38,640 So in this video, we're going to review 20 00:00:38,640 --> 00:00:40,800 some frequently used network configurations, 21 00:00:40,800 --> 00:00:43,530 and also learn how you can troubleshoot things in Linux 22 00:00:43,530 --> 00:00:45,240 using network commands. 23 00:00:45,240 --> 00:00:48,690 Now in Linux, we're going to use a device or system hostname 24 00:00:48,690 --> 00:00:51,270 to easily recognize the machine within the network, 25 00:00:51,270 --> 00:00:53,250 using a human readable format. 26 00:00:53,250 --> 00:00:56,700 For example, I might call my computer Jason's computer 27 00:00:56,700 --> 00:00:59,490 or DNS server or something like that. 28 00:00:59,490 --> 00:01:01,710 That is a human readable format and a hostname 29 00:01:01,710 --> 00:01:03,093 that's easy to understand. 30 00:01:03,093 --> 00:01:06,390 These hostnames can be set up by using a simple command 31 00:01:06,390 --> 00:01:09,030 known as hostnamectl. 32 00:01:09,030 --> 00:01:14,030 To use it, simply type in hostnamectl set-hostname 33 00:01:14,285 --> 00:01:16,890 and then the hostname you want to use. 34 00:01:16,890 --> 00:01:19,320 For a computer to be able to participate on a network, 35 00:01:19,320 --> 00:01:21,180 it has to have a valid identity. 36 00:01:21,180 --> 00:01:24,150 And this means, it has to have a MAC address an IP address, 37 00:01:24,150 --> 00:01:25,500 and a hostname. 38 00:01:25,500 --> 00:01:28,140 IP addresses are going to be configured on your system 39 00:01:28,140 --> 00:01:30,960 using either static or dynamic configurations. 40 00:01:30,960 --> 00:01:32,430 If you do it statically, 41 00:01:32,430 --> 00:01:35,400 you have to set the IP address, the subnet mask, 42 00:01:35,400 --> 00:01:38,040 the location of the default gateway, which is the router 43 00:01:38,040 --> 00:01:40,500 and the location of one or more DNS servers, 44 00:01:40,500 --> 00:01:43,620 so your machine can convert names into numbers. 45 00:01:43,620 --> 00:01:45,720 Now, if you don't want to do all this statically 46 00:01:45,720 --> 00:01:47,970 and there's a DHCP server on your network, 47 00:01:47,970 --> 00:01:50,160 you can simply use dynamic assignments, 48 00:01:50,160 --> 00:01:53,280 and that way, your machine can reach out to the DHTP server 49 00:01:53,280 --> 00:01:56,730 and configure itself with these four pieces of information. 50 00:01:56,730 --> 00:01:58,770 Anytime you have an error or misconfiguration 51 00:01:58,770 --> 00:02:00,660 in any one of these four values, 52 00:02:00,660 --> 00:02:01,710 it means your system 53 00:02:01,710 --> 00:02:04,950 is not going to be able to operate properly on that network. 54 00:02:04,950 --> 00:02:07,890 For example, if you forget to include the DNS server's 55 00:02:07,890 --> 00:02:09,539 IP address in your configuration 56 00:02:09,539 --> 00:02:11,340 on your workstation or server, 57 00:02:11,340 --> 00:02:13,290 this means you're not going to be able to look up things 58 00:02:13,290 --> 00:02:14,970 like diontraining.com, 59 00:02:14,970 --> 00:02:17,190 and you'll only be able to access that web server 60 00:02:17,190 --> 00:02:19,800 if you know its exact IP address. 61 00:02:19,800 --> 00:02:21,390 Now, most Linux distributions, 62 00:02:21,390 --> 00:02:23,390 include a utility called Network Manager, 63 00:02:23,390 --> 00:02:25,890 that helps you set up the proper configuration 64 00:02:25,890 --> 00:02:29,190 for all this data that you need for your network devices. 65 00:02:29,190 --> 00:02:31,650 Network Manager includes three different interfaces 66 00:02:31,650 --> 00:02:33,600 that you can use depending on whether or not 67 00:02:33,600 --> 00:02:35,610 you have a graphical user interface available 68 00:02:35,610 --> 00:02:37,800 on your particular Linux system. 69 00:02:37,800 --> 00:02:40,350 Now, the most fundamental version of Network Manager 70 00:02:40,350 --> 00:02:43,260 is going to be known as nmcli. 71 00:02:43,260 --> 00:02:45,330 This is a command line interface tool 72 00:02:45,330 --> 00:02:46,950 for the Network Manager. 73 00:02:46,950 --> 00:02:49,080 The nmcli tool is going to contain 74 00:02:49,080 --> 00:02:51,000 lots of different sub-commands as well, 75 00:02:51,000 --> 00:02:53,310 that'll enable you to view and configure different pieces 76 00:02:53,310 --> 00:02:54,930 of network information. 77 00:02:54,930 --> 00:02:57,300 Now, many times when you're working with a Linux server, 78 00:02:57,300 --> 00:02:59,820 it's not going to have a graphical user interface. 79 00:02:59,820 --> 00:03:01,936 So it's really important for you to get comfortable 80 00:03:01,936 --> 00:03:05,790 using nmcli to manage your network settings. 81 00:03:05,790 --> 00:03:08,370 Like I said, there's lots of different sub-commands 82 00:03:08,370 --> 00:03:10,740 underneath the nmcli tool. 83 00:03:10,740 --> 00:03:12,990 This includes the general status sub-command 84 00:03:12,990 --> 00:03:14,250 which is used to view a summary 85 00:03:14,250 --> 00:03:16,200 of your network connectivity data. 86 00:03:16,200 --> 00:03:18,060 The connection show sub-command, 87 00:03:18,060 --> 00:03:19,887 which is used to view identification information 88 00:03:19,887 --> 00:03:22,350 for each Network Interface Card. 89 00:03:22,350 --> 00:03:24,570 The con up device ID sub-command, 90 00:03:24,570 --> 00:03:26,370 which is used to enable the specified NIC 91 00:03:26,370 --> 00:03:28,590 and put it into an on position. 92 00:03:28,590 --> 00:03:30,870 The con down device ID sub-command 93 00:03:30,870 --> 00:03:33,390 is going to be used to disable that specified NIC. 94 00:03:33,390 --> 00:03:35,880 The con edit device ID will allow you to enter 95 00:03:35,880 --> 00:03:37,080 an interactive mode 96 00:03:37,080 --> 00:03:39,030 where you can configure the specified NIC 97 00:03:39,030 --> 00:03:41,520 and give it information about its characteristics. 98 00:03:41,520 --> 00:03:43,560 And the device status sub-command 99 00:03:43,560 --> 00:03:45,570 is going to be used to display the current status 100 00:03:45,570 --> 00:03:47,880 of each NIC connected in your system. 101 00:03:47,880 --> 00:03:52,290 To run this command, simply use nmcli, the options, 102 00:03:52,290 --> 00:03:55,530 the sub-command and the arguments you want to use. 103 00:03:55,530 --> 00:03:58,590 While Linux administrators often work at the command line, 104 00:03:58,590 --> 00:04:01,290 it's also useful for you to have a visual representation 105 00:04:01,290 --> 00:04:03,090 of network configuration options 106 00:04:03,090 --> 00:04:06,550 and you can do that using nmtui. 107 00:04:06,550 --> 00:04:08,970 nmtui is a command that will call up 108 00:04:08,970 --> 00:04:10,800 a Text-based User Interface 109 00:04:10,800 --> 00:04:14,460 or TUI, Text-based User Interface. 110 00:04:14,460 --> 00:04:17,040 By navigating a Text-based User Interface, 111 00:04:17,040 --> 00:04:19,740 you can use things like the Tab key, the Space bar 112 00:04:19,740 --> 00:04:20,572 and the Enter key 113 00:04:20,572 --> 00:04:23,580 as well as the Arrow keys to navigate through it. 114 00:04:23,580 --> 00:04:24,660 By using the Tab key 115 00:04:24,660 --> 00:04:27,030 you can move your cursor from field to field. 116 00:04:27,030 --> 00:04:29,160 The Arrow keys are going to be used to make selections 117 00:04:29,160 --> 00:04:30,300 within the field. 118 00:04:30,300 --> 00:04:32,160 And the Enter key will activate a setting 119 00:04:32,160 --> 00:04:34,290 such as OK, or Quit. 120 00:04:34,290 --> 00:04:36,750 Your Space bar will be used to check or uncheck 121 00:04:36,750 --> 00:04:40,020 certain check boxes inside of this user interface. 122 00:04:40,020 --> 00:04:42,360 Now, if you have a graphical user environment 123 00:04:42,360 --> 00:04:44,070 you can also launch the Network Manager 124 00:04:44,070 --> 00:04:47,190 inside of a graphical user environment-based tool. 125 00:04:47,190 --> 00:04:49,590 This is really helpful for managing your network connections 126 00:04:49,590 --> 00:04:51,180 on end user workstations 127 00:04:51,180 --> 00:04:53,190 that might be running something like Ubuntu 128 00:04:53,190 --> 00:04:56,460 or one of the other more graphical-based user distributions. 129 00:04:56,460 --> 00:04:59,820 To launch this, simply type in nmgui, 130 00:04:59,820 --> 00:05:02,340 and this will allow that graphical user tool to come up 131 00:05:02,340 --> 00:05:03,360 and then you'll be able to enable 132 00:05:03,360 --> 00:05:06,150 IPv4 or IPv6 configurations 133 00:05:06,150 --> 00:05:08,400 inside the graphical user environment. 134 00:05:08,400 --> 00:05:10,230 From this tool, you'll have access to all 135 00:05:10,230 --> 00:05:11,250 of your network settings 136 00:05:11,250 --> 00:05:13,834 from the comfort of the graphical user environment. 137 00:05:13,834 --> 00:05:16,980 Now, if you're having problems with your network connection 138 00:05:16,980 --> 00:05:18,780 the first thing you need to do to troubleshoot it 139 00:05:18,780 --> 00:05:20,910 is to view your IP address. 140 00:05:20,910 --> 00:05:22,440 You can do this from the command line 141 00:05:22,440 --> 00:05:24,660 using the ifconfig command. 142 00:05:24,660 --> 00:05:27,660 The ifconfig command is going to show the IP address 143 00:05:27,660 --> 00:05:31,140 the subnet mask, the broadcast ID, the MAC address, 144 00:05:31,140 --> 00:05:34,440 the basic performance information and your NIC's name. 145 00:05:34,440 --> 00:05:36,270 This tool will also enable your NIC 146 00:05:36,270 --> 00:05:37,103 and allow it to be placed 147 00:05:37,103 --> 00:05:39,540 in an up or down configuration state. 148 00:05:39,540 --> 00:05:43,350 To use it, simply type ifconfig and then options 149 00:05:43,350 --> 00:05:45,030 and then the interface you want to use 150 00:05:45,030 --> 00:05:48,360 like eth0 for ethernet zero. 151 00:05:48,360 --> 00:05:51,870 Because the ifconfig command is now officially deprecated, 152 00:05:51,870 --> 00:05:52,830 it's actually been replaced 153 00:05:52,830 --> 00:05:55,200 by something known as the IP command. 154 00:05:55,200 --> 00:05:56,700 Now in lots of distributions, 155 00:05:56,700 --> 00:06:00,330 you'll still find both the IP command and ifconfig 156 00:06:00,330 --> 00:06:01,560 and old-timers like me, 157 00:06:01,560 --> 00:06:04,560 we still tend to use ifconfig, just 'cause we're used to it, 158 00:06:04,560 --> 00:06:07,620 but the IP command has officially replaced it, 159 00:06:07,620 --> 00:06:10,530 and it is what you're going to find on most distributions. 160 00:06:10,530 --> 00:06:14,070 Now IP is going to give you similar information to ipconfig. 161 00:06:14,070 --> 00:06:16,770 This includes the IP address, the subnet mask 162 00:06:16,770 --> 00:06:19,440 the MAC address and all those other things I described. 163 00:06:19,440 --> 00:06:22,950 But the IP command is actually much more powerful. 164 00:06:22,950 --> 00:06:25,080 The IP command is really going to be the first tool 165 00:06:25,080 --> 00:06:25,913 you're going to use 166 00:06:25,913 --> 00:06:28,650 in any network troubleshooting on a Linux system. 167 00:06:28,650 --> 00:06:31,224 The IP command uses a lot of sub-commands as well. 168 00:06:31,224 --> 00:06:35,040 For example, you can type ip adder show 169 00:06:35,040 --> 00:06:37,110 and this will show the IP address information 170 00:06:37,110 --> 00:06:38,760 for all of your interfaces. 171 00:06:38,760 --> 00:06:40,800 If you type in ip link, 172 00:06:40,800 --> 00:06:43,200 this is going to show the status of each interface. 173 00:06:43,200 --> 00:06:46,890 If you used ip link set eth1 up, 174 00:06:46,890 --> 00:06:49,170 this would enable the interface eth1 175 00:06:49,170 --> 00:06:52,290 into the upstate and allow communication to begin. 176 00:06:52,290 --> 00:06:55,530 If you use ip link set eth1 down, 177 00:06:55,530 --> 00:06:57,210 this will actually disable that interface 178 00:06:57,210 --> 00:06:58,980 that was identified as eth1, 179 00:06:58,980 --> 00:07:01,050 so you can do other configurations to it. 180 00:07:01,050 --> 00:07:03,870 Like I said, there's a lot inside of the IP command. 181 00:07:03,870 --> 00:07:06,000 And so, if you look through the man page for IP 182 00:07:06,000 --> 00:07:07,140 you're going to get much more comfortable 183 00:07:07,140 --> 00:07:09,720 with all the different options based on what you need to do 184 00:07:09,720 --> 00:07:11,160 at a given time. 185 00:07:11,160 --> 00:07:13,470 To use the basic structure of the IP command, 186 00:07:13,470 --> 00:07:15,840 you're going to type ip, the options, 187 00:07:15,840 --> 00:07:17,550 the object you want to interface with 188 00:07:17,550 --> 00:07:19,502 and the sub-command to interact with it. 189 00:07:19,502 --> 00:07:21,480 Now, the last one we need to talk about 190 00:07:21,480 --> 00:07:23,700 is known as iwconfig. 191 00:07:23,700 --> 00:07:26,160 The iwconfig command is used to provide 192 00:07:26,160 --> 00:07:28,950 wireless network interface card configurations. 193 00:07:28,950 --> 00:07:30,780 So it works a lot like ifconfig, 194 00:07:30,780 --> 00:07:34,290 but it only works for wireless network cards. 195 00:07:34,290 --> 00:07:36,030 By using iwconfig, 196 00:07:36,030 --> 00:07:38,340 you can configure things like the SSID, 197 00:07:38,340 --> 00:07:39,510 the encryption information 198 00:07:39,510 --> 00:07:42,900 and other things that are specific to a wireless connection. 199 00:07:42,900 --> 00:07:47,400 To run iwconfig, simply type in iwconfig, the options 200 00:07:47,400 --> 00:07:49,170 and the interface you want to interact with, 201 00:07:49,170 --> 00:07:53,160 such as wlan0 for wireless LAN0. 202 00:07:53,160 --> 00:07:54,840 Some common sub-command options here 203 00:07:54,840 --> 00:07:57,150 would be things like nick and a name. 204 00:07:57,150 --> 00:07:58,680 By adding nick and a name, 205 00:07:58,680 --> 00:08:00,060 it will let you give a nickname 206 00:08:00,060 --> 00:08:02,190 to your Network Interface Card. 207 00:08:02,190 --> 00:08:03,900 Or mode and a mode. 208 00:08:03,900 --> 00:08:06,000 This option is used to set the operating mode 209 00:08:06,000 --> 00:08:07,770 for that Network Interface Card, 210 00:08:07,770 --> 00:08:09,930 based on the networking topology you're using. 211 00:08:09,930 --> 00:08:11,760 Or freq and a number. 212 00:08:11,760 --> 00:08:14,040 This option is used to set the wifi frequency 213 00:08:14,040 --> 00:08:16,320 that's going to be used by your wireless card. 214 00:08:16,320 --> 00:08:17,790 Channel and a number. 215 00:08:17,790 --> 00:08:19,530 This is used to set the wifi channel 216 00:08:19,530 --> 00:08:21,510 that's going to be used by your wireless card. 217 00:08:21,510 --> 00:08:23,280 And retry and a number. 218 00:08:23,280 --> 00:08:25,380 This option is used to set the maximum number 219 00:08:25,380 --> 00:08:27,710 of MAC retransmissions for the NIC. 220 00:08:27,710 --> 00:08:29,190 Now, it's important to realize 221 00:08:29,190 --> 00:08:31,200 that when you're using the Network Manager, 222 00:08:31,200 --> 00:08:34,020 this will actually save your settings into a file, 223 00:08:34,020 --> 00:08:36,539 they'll get loaded up the next time the system boots, 224 00:08:36,539 --> 00:08:40,289 but some of the other commands like ifconfig, iwconfig, 225 00:08:40,289 --> 00:08:42,900 ip and things like that will only operate 226 00:08:42,900 --> 00:08:44,910 while the computer is already booted 227 00:08:44,910 --> 00:08:46,680 and it won't save those settings. 228 00:08:46,680 --> 00:08:49,380 So if you have a configuration that you want to be applied 229 00:08:49,380 --> 00:08:51,870 every single time you're going to boot up the system, 230 00:08:51,870 --> 00:08:54,570 you can actually go in and manually edit the files 231 00:08:54,570 --> 00:08:59,570 inside the /etc/sysconfig/network-scripts directory. 232 00:09:00,210 --> 00:09:03,150 Under that directory, you'll find a listing of files 233 00:09:03,150 --> 00:09:08,130 called ifcfg- and then some sort of identifier. 234 00:09:08,130 --> 00:09:10,470 For example, here you can see that I have a file 235 00:09:10,470 --> 00:09:12,300 that I've concatenated to the screen, 236 00:09:12,300 --> 00:09:14,160 and you'll see the different contents of this file 237 00:09:14,160 --> 00:09:16,740 including the fact that this is of TYPE-Ethernet. 238 00:09:16,740 --> 00:09:18,990 The fact that we're not using BOOTPROTO. 239 00:09:18,990 --> 00:09:21,870 Now BOOTPROTO actually stands for boot protocol. 240 00:09:21,870 --> 00:09:23,370 So since this is set as none 241 00:09:23,370 --> 00:09:25,410 this means this is a static assignment. 242 00:09:25,410 --> 00:09:27,930 I want this particular machine which is a server 243 00:09:27,930 --> 00:09:30,090 to always have the same IP address. 244 00:09:30,090 --> 00:09:31,320 As you go lower down, 245 00:09:31,320 --> 00:09:33,720 you'll see the name of this is eth0, 246 00:09:33,720 --> 00:09:35,520 and that's why I want this Network Interface Card 247 00:09:35,520 --> 00:09:37,873 to be referred to as by the operating system. 248 00:09:37,873 --> 00:09:39,900 You see ONBOOT=yes. 249 00:09:39,900 --> 00:09:42,720 This means when I boot up, I want this script to run. 250 00:09:42,720 --> 00:09:44,310 And then you see a HWADDR, 251 00:09:44,310 --> 00:09:47,040 that is the MAC address for this network interface card. 252 00:09:47,040 --> 00:09:50,263 Then I have IPADDR0=192.168.1.10. 253 00:09:52,500 --> 00:09:54,660 This is the first of the four pieces of information 254 00:09:54,660 --> 00:09:56,340 I have to statically assign, 255 00:09:56,340 --> 00:10:00,450 since I didn't enable DHCP under the BOOTPROTO option. 256 00:10:00,450 --> 00:10:03,390 Next I have PREFIX0=24. 257 00:10:03,390 --> 00:10:04,948 This is setting my subnet mask. 258 00:10:04,948 --> 00:10:07,740 Since it's a /24 CIDR notation 259 00:10:07,740 --> 00:10:09,090 which is what I'm using here, 260 00:10:09,090 --> 00:10:13,980 that means my sub mask is actually 255.255.255.0. 261 00:10:13,980 --> 00:10:16,320 This is a default class C range. 262 00:10:16,320 --> 00:10:17,790 Next, you'll see the gateway. 263 00:10:17,790 --> 00:10:21,630 GATEWAY0 is assigned to 192.168.1.1. 264 00:10:21,630 --> 00:10:24,510 And then, you'll see I have DNS1 and DNS2. 265 00:10:24,510 --> 00:10:27,060 I have one internal DNS server I'm going to refer to, 266 00:10:27,060 --> 00:10:28,080 and if that doesn't work 267 00:10:28,080 --> 00:10:31,830 I'm going to point them to Google's DNS at 8.8.8.8. 268 00:10:31,830 --> 00:10:35,310 You'll see there, my intro domain name is diontraining.com. 269 00:10:35,310 --> 00:10:38,520 And then, we also some information for IPv6. 270 00:10:38,520 --> 00:10:40,590 By setting all of this into this file 271 00:10:40,590 --> 00:10:44,370 at /etc/sysconfig/network-scripts, 272 00:10:44,370 --> 00:10:47,790 I'm going to be able to load this up every time my system boots 273 00:10:47,790 --> 00:10:49,170 and it will configure this system 274 00:10:49,170 --> 00:10:50,943 with this static IP address. 275 00:10:51,834 --> 00:10:53,970 Now you may be wondering if this was a workstation 276 00:10:53,970 --> 00:10:55,560 and I wanted to use DHCP on it, 277 00:10:55,560 --> 00:10:56,850 how would I do that? 278 00:10:56,850 --> 00:10:59,820 Well, where it says BOOTPROTO=none, 279 00:10:59,820 --> 00:11:02,190 I would simply change that to either BOOTP, 280 00:11:02,190 --> 00:11:04,170 if I'm using the boot strap protocol 281 00:11:04,170 --> 00:11:08,280 or I would enter DHCP if I want to use a DHCP server 282 00:11:08,280 --> 00:11:11,403 to do my automated configuration using a dynamic assignment. 283 00:11:12,270 --> 00:11:14,460 So in summary, there's really four things 284 00:11:14,460 --> 00:11:16,200 I want you to take away from this lesson. 285 00:11:16,200 --> 00:11:18,240 There are four main tools you're going to use 286 00:11:18,240 --> 00:11:20,790 when interacting and connecting to a network. 287 00:11:20,790 --> 00:11:22,650 You can either use the Network Manager 288 00:11:22,650 --> 00:11:24,270 in any of its three forms, 289 00:11:24,270 --> 00:11:26,640 the command line, the Text User Interface, 290 00:11:26,640 --> 00:11:28,440 or the graphical user interface, 291 00:11:28,440 --> 00:11:31,979 or you can use the older ifconfig, the newer IP, 292 00:11:31,979 --> 00:11:35,634 or if you're using a wireless card, it'll be iwconfig. 293 00:11:35,634 --> 00:11:38,070 All these are tools that you should be comfortable with, 294 00:11:38,070 --> 00:11:39,510 because at some point in your career 295 00:11:39,510 --> 00:11:41,640 you're going to have to use them to configure the network 296 00:11:41,640 --> 00:11:43,893 on your Linux servers and workstations.