1 00:00:02,580 --> 00:00:07,019 Before I can actually test my script, I have some setup to do. So, I want to make 2 00:00:07,019 --> 00:00:11,070 sure that I have /etc/hosts entries for the servers that I'm going to be calling 3 00:00:11,070 --> 00:00:15,700 by name, and one way we can do this is with echo... 4 00:00:19,300 --> 00:00:24,640 and combine that with sudo tee -a /etc/hosts. 5 00:00:32,300 --> 00:00:34,250 Okay, that looks good. 6 00:00:34,250 --> 00:00:41,260 Let's see if I can ping them by name. Okay, 10.9.8.11 for server01, 7 00:00:41,260 --> 00:00:46,800 and I can ping server02 as well when that corresponds to that 10.9.8.12 8 00:00:46,800 --> 00:00:50,810 address, so that looks good. So now, the next thing I need to do is configure 9 00:00:50,810 --> 00:00:56,090 SSH authentication, if I haven't. And this is a new server - I just created it from 10 00:00:56,090 --> 00:00:59,690 scratch, as you saw just a couple of minutes ago - so i need to create a key 11 00:00:59,690 --> 00:01:05,330 pair on my admin01 server. So, I'll do that with ssh-keygen. I'm just going 12 00:01:05,330 --> 00:01:09,920 to accept the default options here. I'm not going to use a passphrase because I want 13 00:01:09,920 --> 00:01:15,020 to execute commands on remote systems without having to enter a passphrase. Now 14 00:01:15,020 --> 00:01:19,450 I need to copy that public key to our servers, so I'm going to copy it to 15 00:01:19,450 --> 00:01:25,430 server01. Yes, I'm going to trust that key, and then I'm going to type in 16 00:01:25,430 --> 00:01:28,250 "vagrant" for the password. I'm going to do the same thing for 17 00:01:28,250 --> 00:01:34,100 server02 - "yes", and the password is "vagrant". So now I should be able to 18 00:01:34,100 --> 00:01:38,450 execute a command on one of those systems without a password, so if I do 19 00:01:38,450 --> 00:01:42,460 ssh server01 and i execute the hostname command - 20 00:01:42,460 --> 00:01:48,440 whoops, if I type the hostname correctly - then it will execute on the remote system 21 00:01:48,440 --> 00:01:52,300 and return its host name, which is server01. Do the same thing with server02. 22 00:01:52,300 --> 00:01:57,740 Connects remotely, executes command, exits, and we're back to admin01. So, this 23 00:01:57,740 --> 00:02:04,490 is looking good. So here I am in my /vagrant folder, and I want to create this 24 00:02:04,490 --> 00:02:09,380 list of default servers that we coded for in our script. So I'm just going to 25 00:02:09,380 --> 00:02:18,320 do this: server01, then add server02. Now, the single greater-than sign 26 00:02:18,320 --> 00:02:22,850 truncates or overrides a file, so if that servers file existed it would have been 27 00:02:22,850 --> 00:02:26,780 zeroed out and then the contents of the echo command would have been stored 28 00:02:26,780 --> 00:02:31,400 in that file. With the double greater-than signs, it appends to 29 00:02:31,400 --> 00:02:37,250 whatever's in that file. So here we have server01 and server02 in our 30 00:02:37,250 --> 00:02:41,870 file. Now we're ready to test our script. Of course. the first time we execute our 31 00:02:41,870 --> 00:02:46,510 script, we want to make sure it has the proper permissions. 32 00:02:47,470 --> 00:02:53,450 Let's test to see if our check about whether or not it was run with root 33 00:02:53,450 --> 00:02:59,400 privileges works. So, we'll run it with sudo. It says, "Do not execute this script 34 00:02:59,400 --> 00:03:05,330 as root. Use the -s option instead," and it gives us our usage statement, and of 35 00:03:05,330 --> 00:03:09,410 course it should exit with a non zero exit status, which it does. So, that looks 36 00:03:09,410 --> 00:03:13,430 like it's working perfectly. Now, let's make sure the script displays a usage 37 00:03:13,430 --> 00:03:18,770 message if we don't supply a command to execute on the list of servers. So, if we 38 00:03:18,770 --> 00:03:23,180 run this command without any options or any commands, it should show us that 39 00:03:23,180 --> 00:03:26,450 usage statement. And it does, so that looks good. 40 00:03:26,450 --> 00:03:32,120 Now, let's try our script with an invalid option. Let's do this: run-everywhere.sh -x, 41 00:03:32,120 --> 00:03:36,110 and we'll say the "hostname" command is what we want to execute everywhere, but 42 00:03:36,110 --> 00:03:41,210 it turns out -x is an invalid option, and getopts catches that, and our script 43 00:03:41,210 --> 00:03:47,090 looks good. Okay, so this time let's execute this script the way it's supposed to be 44 00:03:47,090 --> 00:03:50,930 executed. So, we'll give the name of our script and the command we want executed 45 00:03:50,930 --> 00:03:55,850 on all the remote systems. So, sure enough, it executes the hostname command on 46 00:03:55,850 --> 00:03:59,930 server01, which returns of course server01. and the hostname command on 47 00:03:59,930 --> 00:04:05,630 server02, which returns server02. Now let's execute the script using the dry 48 00:04:05,630 --> 00:04:11,300 run option, which I opted to use the -n for. By the way, I use that because it's 49 00:04:11,300 --> 00:04:15,650 a familiar option to me with some other Linux commands - for example, rsync has 50 00:04:15,650 --> 00:04:19,730 -n for dry run, there are some other examples - so you could have probably used 51 00:04:19,730 --> 00:04:24,680 -d if you wanted to, but it seems to be a convention, at least, to use -n for a 52 00:04:24,680 --> 00:04:32,900 dry run option. Anyway, enough of that aside, let's try it out in our script. 53 00:04:32,900 --> 00:04:38,000 So, it would have executed ssh -o "ConnectTimeout=2" server01 54 00:04:38,000 --> 00:04:41,289 and then the "hostname" command. Now, you may not notice it here, 55 00:04:41,289 --> 00:04:45,009 but there is actually an additional space here, and that's because we have a 56 00:04:45,009 --> 00:04:50,530 space here, and then the $SUDO variable (for which we didn't use -s, so it's not set, so 57 00:04:50,530 --> 00:04:54,340 it doesn't get displayed), and then a space after that $SUDO variable. So we end 58 00:04:54,340 --> 00:04:58,599 up with two spaces here. So that's how that's going to work, by the way. 59 00:04:58,599 --> 00:05:04,120 Okay, let's use the -v option, so we'll do this: run-everywhere.sh -v. Let's use the 60 00:05:04,120 --> 00:05:08,650 "uptime" command that displays how long a system has been up, and it's load average, 61 00:05:08,650 --> 00:05:11,889 and how many users are logged in, and that sort of thing - pretty simple command, 62 00:05:11,889 --> 00:05:16,539 can be kind of interesting. Let's see what happens. Okay, server01 has been 63 00:05:16,539 --> 00:05:20,979 up 42 minutes, server02 has been up 41 minutes, and load average is zero because 64 00:05:20,979 --> 00:05:25,810 nothing's going on on those systems. Let's try to combine some options like 65 00:05:25,810 --> 00:05:35,050 the -n and -s options. So, -n is a dry run, -s is for sudo. So "-ns id", and the 66 00:05:35,050 --> 00:05:38,949 command that would have been executed would have been that ssh with the ssh 67 00:05:38,949 --> 00:05:43,090 options, the server name, and then the SUDO variable, which evaluates to "sudo", 68 00:05:43,090 --> 00:05:48,550 and then the command. So, again, here we had two spaces, here we have a space, and 69 00:05:48,550 --> 00:05:53,050 then the contents of that SUDO variable, and another space. So, again, that's how 70 00:05:53,050 --> 00:06:03,520 that is going to work. This time, let's run the "id" command with -v. If we didn't 71 00:06:03,520 --> 00:06:07,090 use the -v option in this particular case the output is the same, so we 72 00:06:07,090 --> 00:06:10,270 wouldn't have known what servers the output was coming from. 73 00:06:10,270 --> 00:06:14,710 So using this -v option can help with that, so that's kind of why we coded it 74 00:06:14,710 --> 00:06:20,620 in here in our little script. Let's create our own little mini server list 75 00:06:20,620 --> 00:06:25,810 here. We'll just put server01 into that list, and we'll just call this list test, 76 00:06:25,810 --> 00:06:30,370 cat test, okay, it only has one server in there, and then let's go ahead and use 77 00:06:30,370 --> 00:06:35,550 that list and execute a command on that list. 78 00:06:35,550 --> 00:06:41,529 So, again, just one server in the list, it looped over that list - again, just one 79 00:06:41,529 --> 00:06:45,520 doesn't make a lot of sense, but if you have multiple servers then you can use 80 00:06:45,520 --> 00:06:48,820 different lists if you want - and then it executed the "hostname" command that we 81 00:06:48,820 --> 00:06:53,380 specified. So, that looks good. Now, let's test the case where we provide some 82 00:06:53,380 --> 00:07:05,349 invalid data. So, let's say, run-everywhere.sh to a file that doesn't exist. Okay, it looks 83 00:07:05,349 --> 00:07:11,800 like our check worked: Can't open the server list file /path/to/nowhere - 84 00:07:11,800 --> 00:07:14,770 of course, that file is made-up and fake and doesn't 85 00:07:14,770 --> 00:07:19,510 exist, so again our script is working as it should. Now, let's quickly create a 86 00:07:19,510 --> 00:07:24,279 "test1" account on all the servers in our server list, and of course creating 87 00:07:24,279 --> 00:07:29,440 accounts requires superuser or root privileges. Okay, so we'll run our command with 88 00:07:29,440 --> 00:07:33,610 the superuser privileges, we'll run the useradd command, and we'll pass it the name 89 00:07:33,610 --> 00:07:38,080 of the account we want to create, which is "test1". So the useradd command 90 00:07:38,080 --> 00:07:42,729 doesn't generate any output unless it encounters an error, and it looks like no 91 00:07:42,729 --> 00:07:47,320 errors were displayed, so how do we know if this worked? Well, one way we can figure 92 00:07:47,320 --> 00:07:50,979 it out is by running a command everywhere, and that command will be "id" 93 00:07:50,979 --> 00:07:56,320 against the username "test1" to see if it was created. So, sure enough, we get the 94 00:07:56,320 --> 00:08:00,279 exact same output from both of those systems because the account was created 95 00:08:00,279 --> 00:08:05,169 exactly the same on both of those systems. Now, let's say you want to create 96 00:08:05,169 --> 00:08:11,680 a "test2" account with a comment of "Test Two" on all the servers. Because we want 97 00:08:11,680 --> 00:08:16,300 to use a quoted string on the remote system - because we're going to quote "Test Two" 98 00:08:16,300 --> 00:08:21,339 for our comment - we have to put that command in quotes. And to quote a quote, 99 00:08:21,339 --> 00:08:25,630 use the opposing quotation mark. Now, let me just demonstrate that to you on 100 00:08:25,630 --> 00:08:30,070 the command line. So, if we do this: echo double quote, single quote, 101 00:08:30,070 --> 00:08:35,709 Test Two, single quote, double quote, what we get displayed is, single quote, Test Two, 102 00:08:35,709 --> 00:08:40,930 single quote. So, we're using the opposite quotation mark if we want single 103 00:08:40,930 --> 00:08:44,169 quotations to be displayed while we encapsulate those in double quotation 104 00:08:44,169 --> 00:08:49,939 marks, and if we want to do the opposite, Test Two here with double quotation 105 00:08:49,939 --> 00:08:53,779 marks, we encapsulate those with single quotation marks. All right, hopefully that 106 00:08:53,779 --> 00:08:57,740 makes some sense. So, if we want to preserve our quotes for the argument to 107 00:08:57,740 --> 00:09:01,790 the -c option to the useradd command, we need to make sure that they are 108 00:09:01,790 --> 00:09:07,490 quoted. So how we would do this is this: run-everywhere.sh - let's do a dry run to see 109 00:09:07,490 --> 00:09:10,970 what would get executed, so we can test to make sure we have our quotes right on 110 00:09:10,970 --> 00:09:14,720 the command line before we blast this command on every server and potentially 111 00:09:14,720 --> 00:09:18,319 have an account created that doesn't have the right information, or we 112 00:09:18,319 --> 00:09:22,220 accidentally create the wrong account and so on. So, let's do the dry run option. 113 00:09:22,220 --> 00:09:27,000 We need sudo privileges, or we want to use sudo privileges here. 114 00:09:34,500 --> 00:09:40,220 Okay, so what would have gotten executed would be ssh with our SSH options, the server name, 115 00:09:40,220 --> 00:09:45,379 then "sudo useradd -c", and sure enough, our comment is enclosed in quotation 116 00:09:45,379 --> 00:09:50,269 marks, just like we need it on the remote system. So, this is going to work for us. 117 00:09:50,269 --> 00:09:54,649 So now, what we need to do is just go back up here, eliminate our dry run 118 00:09:54,649 --> 00:10:01,009 option, and let it execute as root on those remote systems. Now, let's see if it 119 00:10:01,009 --> 00:10:09,470 got created. And sure enough, it did, and let's run this with the -v option, and you 120 00:10:09,470 --> 00:10:14,269 see exactly what server is generating this output. So sure enough, server01 says 121 00:10:14,269 --> 00:10:17,089 we have a test2 account with an ID of 1002, 122 00:10:17,089 --> 00:10:22,100 as does server02. We could also do this: we could run-everywhere.sh, 123 00:10:22,100 --> 00:10:25,939 -v option to display our server name, and then we'll just tail the last two 124 00:10:25,939 --> 00:10:29,929 entries in the /etc/passwd file, and we should see our two accounts that we 125 00:10:29,929 --> 00:10:35,120 created: a test1 account that we did not supply a comment for, and a test2 126 00:10:35,120 --> 00:10:40,279 account for which we had to be careful about our quotation marks. Now, let's test 127 00:10:40,279 --> 00:10:45,319 our script even further by executing a command that doesn't exist, and we want 128 00:10:45,319 --> 00:10:49,500 to make sure that our command exits with a non-zero exit status. So let's 129 00:10:49,500 --> 00:10:53,569 run-everywhere.sh - I hope this command doesn't exist on your server. If it does, 130 00:10:53,569 --> 00:10:59,860 well, I'll be darned. Okay, sure enough, "i-like-eggs" is not a 131 00:10:59,860 --> 00:11:05,740 command on server01 or server02, and let's look at our return status. Sure 132 00:11:05,740 --> 00:11:10,839 enough, our script exited with a nonzero exit status, so this is exactly what we 133 00:11:10,839 --> 00:11:15,250 want to do. Now, here's another test we can do. Let's say one of our servers is 134 00:11:15,250 --> 00:11:19,690 down, and what's going to happen when we try to execute a command to that server? 135 00:11:19,690 --> 00:11:24,220 Well, let's go ahead and exit out of admin01. Now I'm back to my local 136 00:11:24,220 --> 00:11:32,380 system, be it Mac, Windows, or Linux. Then I'm going to halt server02. By the way, 137 00:11:32,380 --> 00:11:35,740 if you run "vagrant halt" without specifying a server, it's going to halt 138 00:11:35,740 --> 00:11:40,000 all the servers, or all the virtual machines, defined in your Vagrantfile. I 139 00:11:40,000 --> 00:11:43,899 want to limit this command to just one server, that's why I specified it here on 140 00:11:43,899 --> 00:11:47,680 the command line. Likewise, with ssh, I need to specify what 141 00:11:47,680 --> 00:11:52,600 server I'm going to. I'm going to get into admin01. Let's go back to our 142 00:11:52,600 --> 00:11:57,459 shared vagrant folder, and this time let's do run-everywhere.sh -v and use the 143 00:11:57,459 --> 00:12:03,910 "uptime" command. So, server01 has been up 51 minutes, and server02, the ssh timed 144 00:12:03,910 --> 00:12:07,990 out - remember we set the time out to be 2 seconds here. And let's check the exit 145 00:12:07,990 --> 00:12:12,670 status of our script. So, it exits with a nonzero exit status. So, if there is a 146 00:12:12,670 --> 00:12:17,019 server along the way that you can't connect to, then you get a nonzero exit 147 00:12:17,019 --> 00:12:19,690 status with your scripts and you know, "Hey, I need to look at that output and 148 00:12:19,690 --> 00:12:24,490 make sure to go and check out that server." Well, that brings us to the end of 149 00:12:24,490 --> 00:12:28,300 this exercise. I hope you enjoyed it! I'll be curious to see what you come up with, 150 00:12:28,300 --> 00:12:32,500 and of course I hope you find a way to put these concepts and techniques 151 00:12:32,500 --> 00:12:36,930 into use into your workflow.