1 00:00:03,250 --> 00:00:09,080 In this lesson you'll learn how to disable delete and archive users on a Linux system. 2 00:00:09,080 --> 00:00:13,910 Now I've already booted up our local user's virtual machine here and I've logged into it. 3 00:00:14,120 --> 00:00:18,470 I'm still in vagrants home directory because I haven't changed into the shared directory of forward 4 00:00:18,470 --> 00:00:21,550 slash vagrant just yet and will do that later in the lesson. 5 00:00:21,560 --> 00:00:25,090 I just want to work in my home directory here for now. 6 00:00:25,340 --> 00:00:31,700 So far we've been using the example of creating users as an excuse to learn all kinds of shell scripting 7 00:00:31,700 --> 00:00:33,740 concepts and techniques. 8 00:00:33,800 --> 00:00:39,230 The last few lessons I've actually been preparing to write a script around deleting users. 9 00:00:39,290 --> 00:00:42,580 The main point isn't to have scripts that can create daily users. 10 00:00:42,590 --> 00:00:46,100 It's to learn techniques that you can use in any shellscript. 11 00:00:46,100 --> 00:00:51,380 Having said that you are going to write a script in the next assignment that will have you deleting 12 00:00:51,380 --> 00:00:54,500 users so you need to know how to delete users. 13 00:00:54,530 --> 00:00:55,870 So let's go ahead and cover that. 14 00:00:55,870 --> 00:01:01,140 Now the command to delete a user from the system is user Del. 15 00:01:01,160 --> 00:01:07,300 Now if you use our normal type command as a regular user you're probably going to get an error. 16 00:01:07,310 --> 00:01:12,170 So if I do this type a user DL says user. 17 00:01:12,170 --> 00:01:13,620 DLL not found. 18 00:01:13,730 --> 00:01:18,520 And let's see what happens with the which command which user DL. 19 00:01:18,580 --> 00:01:25,030 And it says there is no user DL and then it gives our path there which tells us that there's no user 20 00:01:25,030 --> 00:01:28,950 DL and user local bad news or bad news or local Hispanic cetera. 21 00:01:28,960 --> 00:01:34,720 It is our path and it's displaying there so just as the which command tells us the user DEL command 22 00:01:34,750 --> 00:01:37,060 is not in our path. 23 00:01:37,060 --> 00:01:39,780 We talked about paths earlier in the course. 24 00:01:39,880 --> 00:01:42,950 At this point there really is two options. 25 00:01:42,970 --> 00:01:47,840 One the user DEL command really doesn't exist it does not exist. 26 00:01:47,920 --> 00:01:54,030 Or two it in fact does exist but it just exists outside of our current path. 27 00:01:54,160 --> 00:01:58,690 So I quickly want to cover how to find a command that is not in your path because you may run into this 28 00:01:58,690 --> 00:01:59,950 from time to time. 29 00:01:59,950 --> 00:02:06,640 Now most Linux systems have locate installed and configured the locate command searches an index that 30 00:02:06,640 --> 00:02:14,200 is created by the update divi command the update command is typically scheduled to run once a day. 31 00:02:14,200 --> 00:02:20,470 This means that locate doesn't have up to the minute information but on the other hand it's a very fast 32 00:02:20,470 --> 00:02:26,260 it finds things in that pre-created or pre-populated database or index very fast. 33 00:02:26,260 --> 00:02:33,040 So if we do this when we type in the locate user Dell will get some results here and if we look at the 34 00:02:33,040 --> 00:02:40,210 top of our command we can actually see that the command resides in Fort Sless user for Espen forward 35 00:02:40,210 --> 00:02:43,600 slash user Dalle that's actually where the command lives. 36 00:02:43,750 --> 00:02:47,020 Now just to prove that locate isn't using real time data. 37 00:02:47,040 --> 00:02:51,100 Let's create a file called user Del and then try to find it with locate. 38 00:02:51,100 --> 00:02:55,670 So I'm just going to touch user Dell right here in my home directory. 39 00:02:55,720 --> 00:03:01,090 Again the touch command creates a file if it doesn't exists or if the file exists it touches it and 40 00:03:01,090 --> 00:03:03,550 updates its time stamp. 41 00:03:03,550 --> 00:03:11,200 So sure enough user DL is on our system and if we type locate user DL We don't see anything about vagrants 42 00:03:11,200 --> 00:03:12,350 home directory. 43 00:03:12,640 --> 00:03:18,070 So if we force an index update we should be able to find that user Idel file that we placed into vagrants 44 00:03:18,070 --> 00:03:20,390 home directory by using the touch command. 45 00:03:20,560 --> 00:03:26,770 And by the way to run update D-B you need root privileges because what it does is search is the entire 46 00:03:26,770 --> 00:03:33,010 file system and you don't have permissions to every single file as a regular user such that vagrant 47 00:03:33,070 --> 00:03:40,570 is there will do this sudo update DBI and let that run for a second here and once that is done now we 48 00:03:40,570 --> 00:03:48,400 can do locate a user Dell and now at the very top of the output you see Ford slash home vagrant user 49 00:03:48,450 --> 00:03:50,300 Dell that file we just created. 50 00:03:50,560 --> 00:03:57,100 Let me take a step back so I would first use the locate command and actually since I'm looking for a 51 00:03:57,100 --> 00:03:59,380 binary or an executable file. 52 00:03:59,470 --> 00:04:03,730 I would limit my search to only include things in the bin directory. 53 00:04:03,730 --> 00:04:10,390 Let's now take the standard output of the locate command and send it as standard input to the grip command 54 00:04:10,840 --> 00:04:16,040 the grip command displays matches to a pattern and discard everything else. 55 00:04:16,240 --> 00:04:23,590 So if we do locate a user Del pipe that into grap in our search pattern is simply going to be the characters 56 00:04:23,590 --> 00:04:26,260 be in and hit enter. 57 00:04:26,590 --> 00:04:29,500 So this really really narrows it down for us. 58 00:04:29,500 --> 00:04:35,110 We see two possible options and obviously the one at the bottom there user ESPNews or Del is what we're 59 00:04:35,110 --> 00:04:36,170 looking for. 60 00:04:36,190 --> 00:04:41,420 Sometimes the file you're looking for is not in a place where you have read permissions. 61 00:04:41,440 --> 00:04:44,700 The locate command honors those permissions. 62 00:04:44,860 --> 00:04:50,050 So if we do something like this locate dot bash RC and hit enter. 63 00:04:50,050 --> 00:04:55,650 We only see SC scaled up bash RC and then the bash RC in our home directory. 64 00:04:55,780 --> 00:04:58,590 Now let's run that same command with root privileges. 65 00:05:00,730 --> 00:05:07,600 Now we see all the dot bash RC files on the system as the vagrant user we don't have permission to look 66 00:05:07,600 --> 00:05:10,020 inside root's home directory for example. 67 00:05:10,180 --> 00:05:15,310 So if we do this LS Tesch l root bash R C we get an error. 68 00:05:15,310 --> 00:05:16,210 Permission denied. 69 00:05:16,210 --> 00:05:19,160 We can't look at anything in root's home directory by default. 70 00:05:19,450 --> 00:05:23,140 So if we use root permissions we can now see the file. 71 00:05:23,290 --> 00:05:29,980 By the way the quick little thing I did there the double exclamation marks or Bang Bang actually represents 72 00:05:29,980 --> 00:05:32,410 the most recently executed command. 73 00:05:32,440 --> 00:05:36,200 So if you want to execute the most recent command with root privileges. 74 00:05:36,250 --> 00:05:38,490 Use the shortcut Sea-Doo space. 75 00:05:38,500 --> 00:05:39,850 Bang bang. 76 00:05:39,880 --> 00:05:45,760 The command that will be executed actually gets displayed to the screen first and then any output generated 77 00:05:45,760 --> 00:05:48,100 by that command is displayed. 78 00:05:48,100 --> 00:05:55,990 So here we can see that sudo bing bang expands to Sea-Doo space LS shell or slash root for Slash dash 79 00:05:55,990 --> 00:06:00,470 bash RC and then the output of that command follows. 80 00:06:00,550 --> 00:06:03,430 So that's just another quick shell tip for you right there. 81 00:06:03,430 --> 00:06:05,970 Thone in the middle of this lesson. 82 00:06:05,980 --> 00:06:12,100 Anyway my point here is that sometimes you need to use root privileges to find a file because you do 83 00:06:12,100 --> 00:06:16,930 not have permissions to view that file as your own normal regular user. 84 00:06:17,230 --> 00:06:23,170 Let's say locate isn't installed are configured so what would you try next. 85 00:06:23,170 --> 00:06:29,170 Well I would use my knowledge of the Linux file system hierarchy and then start looking in places where 86 00:06:29,170 --> 00:06:30,450 the file might live. 87 00:06:30,610 --> 00:06:36,730 For example if I'm looking for a configuration file I would start looking and forward slash ETSI or 88 00:06:36,730 --> 00:06:38,590 forward slash ATC. 89 00:06:38,770 --> 00:06:43,930 But since we're looking for an executable also called a binary I would look in bin directory. 90 00:06:43,930 --> 00:06:52,820 So let's do this here it looks like Ford slash bin is a symlink to user bin and S-band is actually a 91 00:06:52,820 --> 00:06:59,540 symlink to user Esben and most modern Linux systems this will be the case but on some older Linux distros 92 00:06:59,540 --> 00:07:05,210 or on some Unix systems you might find that they are actually different directories with different contents. 93 00:07:05,210 --> 00:07:11,530 So let's go ahead and look in user bin and see if user data is there. 94 00:07:11,540 --> 00:07:13,600 No no such file or directory. 95 00:07:13,610 --> 00:07:16,880 And by the way when you see no such file a directory please believe it. 96 00:07:16,880 --> 00:07:22,350 It's telling you that the file doesn't exist or the file that you specified does not exist. 97 00:07:22,360 --> 00:07:23,480 Anyway let's try it. 98 00:07:23,480 --> 00:07:25,930 End user Espen user. 99 00:07:26,450 --> 00:07:27,740 Here we don't get an error. 100 00:07:27,740 --> 00:07:32,660 We get some valid LS output that shows us that the file does exist. 101 00:07:32,660 --> 00:07:38,090 Actually I probably could have shortened up my search just a little bit here because user Dell is a 102 00:07:38,090 --> 00:07:44,980 system administration type of command Now system and then commands are usually found in s bin directories. 103 00:07:45,050 --> 00:07:50,720 Normal commands that all users can run are found in bin directories for example LS is a command that 104 00:07:50,810 --> 00:07:51,620 everyone needs. 105 00:07:51,620 --> 00:07:53,570 Not just a system administrator. 106 00:07:53,570 --> 00:07:57,180 So it's found in user bin. 107 00:07:57,270 --> 00:08:03,960 There is another way to find files and that is where the find to command unlike locate find looks at 108 00:08:03,960 --> 00:08:10,710 files in real time which makes it slower than locate but yet up to date there are a lot of options to 109 00:08:10,710 --> 00:08:14,360 the find command and I'm not going to go through each and every one of them. 110 00:08:14,460 --> 00:08:19,290 But here's just a very quick crash course and how to use the find command. 111 00:08:19,320 --> 00:08:25,560 Now the format of the line command is find followed by the path to search in followed by any options 112 00:08:25,560 --> 00:08:27,930 expressions or search patterns. 113 00:08:27,930 --> 00:08:32,170 If you don't get find a path it starts searching in your current directory. 114 00:08:32,370 --> 00:08:35,960 So let's look in the user bin directory Sophies find. 115 00:08:36,030 --> 00:08:39,210 Follow that with a path and then hit enter. 116 00:08:39,210 --> 00:08:43,990 Here it just lists all the files in that directory because we haven't narrowed down our search. 117 00:08:44,010 --> 00:08:49,170 And by the way it not only list the files in that directory it would list any files of any subdirectories 118 00:08:49,170 --> 00:08:51,480 and any files within those subdirectories and so on. 119 00:08:51,510 --> 00:08:55,080 To say it another way find searches recursively. 120 00:08:55,080 --> 00:09:00,650 Now let's tell it the name of the file We're looking for so we can do this find user Espin and there 121 00:09:00,650 --> 00:09:05,250 is an option called Dasch name and then we supply that with the name of the file We're looking for. 122 00:09:05,250 --> 00:09:12,010 We're looking for user Del OK admittedly that was too easy because we already knew where to find the 123 00:09:12,020 --> 00:09:14,540 user command and I was teaching a little bit there. 124 00:09:14,700 --> 00:09:20,730 But if you have no idea where the file exists you can search the entire file system starting at the 125 00:09:20,730 --> 00:09:21,620 root. 126 00:09:21,630 --> 00:09:26,490 I don't necessarily always recommend this approach especially if you're working on a system that has 127 00:09:26,490 --> 00:09:29,990 a lot of files on it but it will work. 128 00:09:30,030 --> 00:09:36,460 So let's do find slacks with a dash name of user Del here. 129 00:09:36,460 --> 00:09:39,470 We're seeing a lot of permission denied errors. 130 00:09:39,580 --> 00:09:45,110 There are two ways around this one is just to send all those error messages to dev null. 131 00:09:45,190 --> 00:09:48,310 So we don't have to look at them and let's try that here now. 132 00:09:48,310 --> 00:09:53,980 So we know that error messages are displayed on standard error and standard error is represented by 133 00:09:53,980 --> 00:09:55,510 a file descriptor too. 134 00:09:55,530 --> 00:10:02,200 So we'll use file descriptor to and redirect that to the bitbucket also called forward slash def afford 135 00:10:02,260 --> 00:10:04,780 slash null and hit enter. 136 00:10:04,780 --> 00:10:09,730 Now we don't get any of those air messages to our screen because they were redirected into dev know 137 00:10:09,730 --> 00:10:16,260 which does nothing with them it just Those them away and we're left with all the matches to the user 138 00:10:16,270 --> 00:10:19,140 Dell name without any of the errors. 139 00:10:19,150 --> 00:10:22,370 So in this particular case we find the file that we're looking for. 140 00:10:22,420 --> 00:10:28,300 But what if the file we were looking for is really somewhere where we need root permissions or a place 141 00:10:28,300 --> 00:10:33,520 where our particular user does not have permissions to view in that particular case you want to run 142 00:10:33,520 --> 00:10:34,790 the command as a route. 143 00:10:34,930 --> 00:10:35,840 So we can do this. 144 00:10:35,860 --> 00:10:39,900 So you do find slash and the name of use of Dell. 145 00:10:40,030 --> 00:10:44,390 There is so much more to the find command and there's so much more you can do. 146 00:10:44,490 --> 00:10:49,020 But this little crash course will really get you started and pointed in the right direction. 147 00:10:49,300 --> 00:10:54,820 So at this point we've proven that user Dell exists even if the type in which commands do not provide 148 00:10:54,820 --> 00:10:59,050 any information on those commands due to the settings of our path. 149 00:10:59,110 --> 00:11:02,180 However user Dell will be and root's path. 150 00:11:02,350 --> 00:11:04,300 So I'm going to switch to the root user. 151 00:11:04,360 --> 00:11:10,350 You're on the vaguer system by the way the root password is also vagrant V.A g r E.A. and hit enter 152 00:11:10,360 --> 00:11:17,520 now the root user and if I type type cache user or Del I'm going to see where the user del command resides. 153 00:11:17,650 --> 00:11:20,520 All right I'm going to get out of the root account here and back to vagrant.