1 00:00:00,000 --> 00:00:02,490 Besides performing basic file operations 2 00:00:02,490 --> 00:00:04,530 like reading, writing, and moving, 3 00:00:04,530 --> 00:00:08,130 we can also manipulate files so that they're more useful. 4 00:00:08,130 --> 00:00:09,510 So, we're just going to go over a few ways 5 00:00:09,510 --> 00:00:12,500 to accomplish this, as well as get metadata about the files. 6 00:00:12,500 --> 00:00:14,580 So the first thing we're going to do is we're going to just look 7 00:00:14,580 --> 00:00:15,480 at a software list. 8 00:00:15,480 --> 00:00:19,200 So, we're just going to use this n option just 9 00:00:19,200 --> 00:00:21,060 to see the number of lines 10 00:00:21,060 --> 00:00:22,860 and going to look at this really quick. 11 00:00:26,010 --> 00:00:28,977 So you see, we have a clear view of the software list 12 00:00:28,977 --> 00:00:30,780 and I added the n option 13 00:00:30,780 --> 00:00:32,159 so we can see the number list 14 00:00:32,159 --> 00:00:32,993 and that's going to be more useful later on. 15 00:00:32,993 --> 00:00:35,460 What we're going to do next 16 00:00:35,460 --> 00:00:36,960 is we're going to use the sort command 17 00:00:36,960 --> 00:00:38,370 And what that is going to do 18 00:00:38,370 --> 00:00:42,000 is sort the file alphabetical order. 19 00:00:42,000 --> 00:00:44,880 And we're going to use the K option 20 00:00:44,880 --> 00:00:47,040 which refers to the column. 21 00:00:47,040 --> 00:00:50,013 So, column one of the software list. 22 00:00:54,810 --> 00:00:56,370 Now, we see this isn't perfect. 23 00:00:56,370 --> 00:00:59,280 There's more options available to make sure 24 00:00:59,280 --> 00:01:01,500 we're not including the header, but you see 25 00:01:01,500 --> 00:01:04,560 that it just data dumps pretty much the entire file 26 00:01:04,560 --> 00:01:05,940 and sorts it from A to Z. 27 00:01:05,940 --> 00:01:09,550 Now, we also do the same thing for the second column 28 00:01:11,310 --> 00:01:15,543 which is going to be pretty much all Ns and a Y. 29 00:01:22,290 --> 00:01:24,960 Next thing we want to do is get some metadata 30 00:01:24,960 --> 00:01:25,860 from this file. 31 00:01:25,860 --> 00:01:28,380 So, we're going to do the word count command. 32 00:01:28,380 --> 00:01:31,440 Now, we're going to do it raw by itself. 33 00:01:31,440 --> 00:01:33,993 So, we're going to use software list3 again. 34 00:01:35,130 --> 00:01:36,570 And if you look at the output, 35 00:01:36,570 --> 00:01:39,960 the first output is the amount of lines in the file, 36 00:01:39,960 --> 00:01:43,020 the second is the amount of words, 37 00:01:43,020 --> 00:01:44,520 and the third is the amount of characters. 38 00:01:44,520 --> 00:01:47,610 Now, this includes all characters, non-printable characters, 39 00:01:47,610 --> 00:01:50,163 anything that the computer uses to process. 40 00:01:51,030 --> 00:01:54,690 So, if we want to see that view so we can see again, 41 00:01:54,690 --> 00:01:59,690 n, software list3, and we see it has 18 lines there, 42 00:02:02,280 --> 00:02:05,040 it's 54 words, 242 characters. 43 00:02:05,040 --> 00:02:07,440 Now again, characters are anything 44 00:02:07,440 --> 00:02:12,360 that's processed by the computer. 45 00:02:12,360 --> 00:02:17,360 So if you look at this display, you'll see that space, tabs, 46 00:02:18,570 --> 00:02:21,180 all these things are characters 47 00:02:21,180 --> 00:02:23,700 and they're encoded to the operating system 48 00:02:23,700 --> 00:02:26,160 so that the computer knows what to do with these things, 49 00:02:26,160 --> 00:02:28,020 how to display that on the screen. 50 00:02:28,020 --> 00:02:29,490 Of course we might not see it, 51 00:02:29,490 --> 00:02:31,800 but this is what the computer sees. 52 00:02:31,800 --> 00:02:34,350 So, all these characters is what's counted 53 00:02:34,350 --> 00:02:36,213 by the word count command. 54 00:02:37,320 --> 00:02:39,240 And again, we can make this very simple 55 00:02:39,240 --> 00:02:40,530 if we just want the word count. 56 00:02:40,530 --> 00:02:44,940 So, we do the w option, software list3 again 57 00:02:44,940 --> 00:02:48,570 and just give us the exact amount of words that we need. 58 00:02:48,570 --> 00:02:49,500 And of course, more options 59 00:02:49,500 --> 00:02:53,160 for lines or characters themselves. 60 00:02:53,160 --> 00:02:54,600 Again, sticking with these same files, 61 00:02:54,600 --> 00:02:58,020 we can also use a command called diff. 62 00:02:58,020 --> 00:03:00,660 So remember, it's going to give us the differentials 63 00:03:00,660 --> 00:03:02,100 between those files. 64 00:03:02,100 --> 00:03:04,410 So, pretty much it's going to let us know which lines 65 00:03:04,410 --> 00:03:06,060 should be added or subtracted 66 00:03:06,060 --> 00:03:09,600 from the first file to match the second file. 67 00:03:09,600 --> 00:03:11,310 So, let's try this out really quick. 68 00:03:11,310 --> 00:03:13,440 So I have a software list I created earlier. 69 00:03:13,440 --> 00:03:16,590 One has less of the software than the other. 70 00:03:16,590 --> 00:03:20,790 So, software list1 is going to have list, 71 00:03:20,790 --> 00:03:22,620 then software list three 72 00:03:22,620 --> 00:03:24,220 'cause I can find these earlier. 73 00:03:26,460 --> 00:03:27,840 And now, what this is telling us 74 00:03:27,840 --> 00:03:32,400 is if you look at the arrows, those arrows pointing 75 00:03:32,400 --> 00:03:35,820 to the right indicate what lines need to be added 76 00:03:35,820 --> 00:03:39,603 to the first file in order to replicate the second file. 77 00:03:40,710 --> 00:03:44,790 So, if you see here, 12, what that means is 78 00:03:44,790 --> 00:03:48,060 after line 12 in software listing one, 79 00:03:48,060 --> 00:03:52,110 add lines 13 through 18 to software listing one 80 00:03:52,110 --> 00:03:54,330 so they can be equivalent. 81 00:03:54,330 --> 00:03:57,090 So again, that's where we've used this cat feature 82 00:03:57,090 --> 00:03:59,310 right with the count 83 00:03:59,310 --> 00:04:02,493 just to verify the correctness of this. 84 00:04:03,570 --> 00:04:05,100 So, we'll see software listing one 85 00:04:05,100 --> 00:04:08,910 has 12 lines and software listing three has 18 lines. 86 00:04:08,910 --> 00:04:11,940 So, it's telling us from lines 13 through 18, 87 00:04:11,940 --> 00:04:15,210 add those to software listing one 88 00:04:15,210 --> 00:04:16,649 in order for them to be equivalent. 89 00:04:16,649 --> 00:04:19,920 Again, this is mostly used when we have a different version 90 00:04:19,920 --> 00:04:21,329 of the same file 91 00:04:21,329 --> 00:04:24,090 and it quickly gives us the differences between the two. 92 00:04:24,090 --> 00:04:26,190 Another command we're going to use is grep. 93 00:04:26,190 --> 00:04:27,420 And we're going to use an example to be able 94 00:04:27,420 --> 00:04:31,230 to pinpoint key information that we would need for a search. 95 00:04:31,230 --> 00:04:34,510 Okay, so we're going to look at this file 96 00:04:36,300 --> 00:04:38,400 and we're going to use the one for the logs, 97 00:04:38,400 --> 00:04:39,840 for the login files. 98 00:04:39,840 --> 00:04:40,673 Okay? 99 00:04:43,470 --> 00:04:46,830 Now we see it gives us a plethora of information, 100 00:04:46,830 --> 00:04:50,790 but sometimes we want to look at specific types of failures 101 00:04:50,790 --> 00:04:54,270 or specific type of errors within a log. 102 00:04:54,270 --> 00:04:58,140 So, we're going to try to look up a failed password attempt. 103 00:04:58,140 --> 00:05:00,970 So, I'm going to try to, I'm going to switch to a user 104 00:05:02,250 --> 00:05:03,480 and I'm going to log in. 105 00:05:03,480 --> 00:05:06,100 I'm going to just try to log in with the wrong password 106 00:05:08,430 --> 00:05:11,370 and I want to pinpoint that in the log. 107 00:05:11,370 --> 00:05:14,010 Okay, so we see you have an authentication failure 108 00:05:14,010 --> 00:05:16,890 when we're trying to log into the ariley account. 109 00:05:16,890 --> 00:05:18,000 So, what we're going to do is we're going 110 00:05:18,000 --> 00:05:21,030 to find this failure in the log. 111 00:05:21,030 --> 00:05:24,780 So, we use the grep failed and we're going to go clear, 112 00:05:24,780 --> 00:05:29,780 log, secure and we can see there towards the bottom 113 00:05:32,160 --> 00:05:35,970 that password check failed for user ariley. 114 00:05:35,970 --> 00:05:40,710 So again, this is a quick way to search through large logs 115 00:05:40,710 --> 00:05:43,410 and get the key information that you need. 116 00:05:43,410 --> 00:05:44,850 Next we're going to go over linking. 117 00:05:44,850 --> 00:05:46,830 Now, there's two ways to do this. 118 00:05:46,830 --> 00:05:50,100 We can either create a hard link from one file to another 119 00:05:50,100 --> 00:05:52,800 or a symbolic link or soft link. 120 00:05:52,800 --> 00:05:54,335 So for example, first thing we want to do, 121 00:05:54,335 --> 00:05:56,580 we're going to make some directories really quick 122 00:05:56,580 --> 00:05:58,803 into the backup folder. 123 00:06:01,470 --> 00:06:02,610 So, we're going to do the backup, 124 00:06:02,610 --> 00:06:07,000 the log, we'll make an authentication one 125 00:06:07,909 --> 00:06:11,043 and we're also going to make up one for just the current year. 126 00:06:14,460 --> 00:06:15,360 All right. 127 00:06:15,360 --> 00:06:16,380 So, we're going to make a copy 128 00:06:16,380 --> 00:06:18,960 of the secure log into our own folder 129 00:06:18,960 --> 00:06:22,020 that we just created in the backup portion. 130 00:06:22,020 --> 00:06:26,477 So, we're going to do sudo copy var log secure. 131 00:06:29,730 --> 00:06:32,703 I want to make sure we put it in our backup log order. 132 00:06:38,430 --> 00:06:39,263 Okay? 133 00:06:42,360 --> 00:06:46,560 Now we're going to go to the backup log, list it out, 134 00:06:46,560 --> 00:06:48,003 make sure that was created. 135 00:06:49,650 --> 00:06:50,734 So, by default without any options, 136 00:06:50,734 --> 00:06:55,734 when you use the link command it's going to create a hard link. 137 00:06:56,100 --> 00:06:57,210 So, let's do that first. 138 00:06:57,210 --> 00:07:00,270 We're going to do the hard link 139 00:07:00,270 --> 00:07:05,270 for the secure folder that we just secure file. 140 00:07:05,450 --> 00:07:06,870 I mean, that we just copied over. 141 00:07:06,870 --> 00:07:11,870 And going to link that to the 2022 secure file. 142 00:07:13,620 --> 00:07:15,480 Now, a hard link again, 143 00:07:15,480 --> 00:07:19,680 is a full copy of the target destination 144 00:07:19,680 --> 00:07:22,770 and a symbolic link is going to be a reference 145 00:07:22,770 --> 00:07:24,900 to that target. 146 00:07:24,900 --> 00:07:26,700 So if that target gets deleted, 147 00:07:26,700 --> 00:07:30,303 then that symbolic link no longer has any information. 148 00:07:31,410 --> 00:07:33,180 Let's just verify that that was created. 149 00:07:33,180 --> 00:07:34,480 So, we're going to do a list. 150 00:07:35,790 --> 00:07:36,993 2022 folder. 151 00:07:39,270 --> 00:07:43,350 And we can see that blue around it indicates 152 00:07:43,350 --> 00:07:44,253 that it's a link. 153 00:07:45,210 --> 00:07:47,477 Now, let's just verify that the secure file 154 00:07:47,477 --> 00:07:49,800 in the authentication folder is the same 155 00:07:49,800 --> 00:07:52,473 as the secure file in the 2022 folder. 156 00:08:01,877 --> 00:08:06,210 We're just going to look at the bottom portion of this. 157 00:08:08,790 --> 00:08:12,480 And do the same thing for the 2022 folder. 158 00:08:12,480 --> 00:08:13,313 Secure file. 159 00:08:18,177 --> 00:08:20,790 And we can see that they're identical. 160 00:08:20,790 --> 00:08:23,340 So, the next thing we want to do to verify this hard link 161 00:08:23,340 --> 00:08:25,500 is we're going to add some information 162 00:08:25,500 --> 00:08:28,680 to the secure file under the authentication folder 163 00:08:28,680 --> 00:08:30,810 and see if it reflects to the secure file 164 00:08:30,810 --> 00:08:32,909 in the 2022 folder. 165 00:08:32,909 --> 00:08:33,750 So, let's do that really quick. 166 00:08:33,750 --> 00:08:34,743 We're going to nano. 167 00:08:45,390 --> 00:08:48,303 Now, we're going to say some simple information like, 168 00:08:52,290 --> 00:08:57,150 use this month, simple enough. 169 00:08:57,150 --> 00:09:00,130 Going to do control O to save this 170 00:09:02,280 --> 00:09:03,780 and then control X to get out. 171 00:09:05,160 --> 00:09:07,380 So, let's verify this really quick by looking 172 00:09:07,380 --> 00:09:12,380 at the first 10 lines of the 2022 folder, the secure file. 173 00:09:15,720 --> 00:09:20,580 And now we see that it has that begin 06, 2022 line 174 00:09:20,580 --> 00:09:22,173 that we input earlier. 175 00:09:23,670 --> 00:09:27,250 Again, just to double check, go to the authentication folder 176 00:09:29,520 --> 00:09:33,240 and we'll see that successfully linked 177 00:09:33,240 --> 00:09:37,500 and remember that these are copies and not just links. 178 00:09:37,500 --> 00:09:39,813 So, we're going to go ahead and remove this file. 179 00:09:42,840 --> 00:09:44,610 Now, we can verify that even 180 00:09:44,610 --> 00:09:47,940 though we deleted the authentication secure file 181 00:09:47,940 --> 00:09:51,180 that the 2022 secure file is still there. 182 00:09:51,180 --> 00:09:52,380 So, let's just list out that folder 183 00:09:52,380 --> 00:09:53,760 just to make sure it's still intact. 184 00:09:53,760 --> 00:09:55,023 The 2022 folder. 185 00:09:56,190 --> 00:09:58,713 Okay, we see our secure file is still intact. 186 00:09:59,610 --> 00:10:01,530 Now we're going to go to our home directory. 187 00:10:01,530 --> 00:10:04,200 Now, this time what we're going to try to do is see 188 00:10:04,200 --> 00:10:05,850 if we can create a link 189 00:10:05,850 --> 00:10:08,640 between the backup file system 190 00:10:08,640 --> 00:10:11,133 and one into our home directory. 191 00:10:12,030 --> 00:10:13,143 We can go sudo link. 192 00:10:18,120 --> 00:10:21,390 And honestly, we should get a error at this point. 193 00:10:21,390 --> 00:10:25,470 Now with hard links, one thing that we have to take account 194 00:10:25,470 --> 00:10:27,690 is the type of file system. 195 00:10:27,690 --> 00:10:30,480 For a symbolic link, we can span different file systems. 196 00:10:30,480 --> 00:10:33,870 For a hard link, these file systems have to be the same. 197 00:10:33,870 --> 00:10:36,570 So, let's check out what the current file systems are. 198 00:10:40,320 --> 00:10:42,060 If you look at the centos root, 199 00:10:42,060 --> 00:10:46,740 so sda2, the root, the mount point, the root folder, 200 00:10:46,740 --> 00:10:49,923 you see the type of file system, it's an XFS. 201 00:10:50,760 --> 00:10:54,030 And the ones we wanted to reference, the backup log, 202 00:10:54,030 --> 00:10:56,310 so look at the mount point all the way to the right 203 00:10:56,310 --> 00:10:58,920 and at the very bottom you'll see the backup log. 204 00:10:58,920 --> 00:11:01,710 The file system type is EXT4. 205 00:11:01,710 --> 00:11:03,360 So, they're incompatible. 206 00:11:03,360 --> 00:11:05,430 So, we will not be able to create a hard link, 207 00:11:05,430 --> 00:11:07,830 but we can create a soft link. 208 00:11:07,830 --> 00:11:09,960 Now we're going to do the same thing, 209 00:11:09,960 --> 00:11:12,243 but again, we're going to create the S option. 210 00:11:15,360 --> 00:11:16,830 And now if we list out our folder, 211 00:11:16,830 --> 00:11:20,013 we see the off auth dash log file as created. 212 00:11:21,570 --> 00:11:22,650 Now we're going to just verify 213 00:11:22,650 --> 00:11:24,960 that that link actually has the information 214 00:11:24,960 --> 00:11:27,273 that we actually want to see from this file. 215 00:11:28,860 --> 00:11:30,180 All right, looks like we have made 216 00:11:30,180 --> 00:11:32,883 a successful symbolic link to that file. 217 00:11:34,170 --> 00:11:36,150 So, here we're going to show the difference 218 00:11:36,150 --> 00:11:39,540 between the hard and soft links 219 00:11:39,540 --> 00:11:43,890 by removing the secure file that's in our 2022 220 00:11:43,890 --> 00:11:47,640 under the backup and see if we're able to still access it 221 00:11:47,640 --> 00:11:50,553 in our off log and our current working directory. 222 00:11:51,810 --> 00:11:52,710 So, let's do that. 223 00:11:57,780 --> 00:11:59,080 All right, that's removed. 224 00:12:00,420 --> 00:12:05,420 Now, let's just try to view the contents of this log. 225 00:12:07,890 --> 00:12:12,120 And we see it says no such file or director exists. 226 00:12:12,120 --> 00:12:14,510 Again, 'cause it's referencing the secure file 227 00:12:14,510 --> 00:12:16,920 in the 2022 folder. 228 00:12:16,920 --> 00:12:20,793 So if we list it out, we'll see we have a broken link. 229 00:12:21,690 --> 00:12:23,440 That's what the flashing indicates. 230 00:12:25,620 --> 00:12:30,330 So again, these soft links reference an existing file. 231 00:12:30,330 --> 00:12:32,130 The hard links create a copy 232 00:12:32,130 --> 00:12:34,440 of the existing file and constantly updates 233 00:12:34,440 --> 00:12:38,820 every time the target file gets updated as well. 234 00:12:38,820 --> 00:12:40,050 This goes for even 235 00:12:40,050 --> 00:12:44,880 if the file name is changed or the location is changed, 236 00:12:44,880 --> 00:12:47,880 the link is not automatically updated . 237 00:12:47,880 --> 00:12:49,380 so you're going to have to go in 238 00:12:49,380 --> 00:12:53,400 and reassociate that link to the new file location 239 00:12:53,400 --> 00:12:54,453 or the new file name. 240 00:12:55,350 --> 00:12:57,060 Let's sum things up. 241 00:12:57,060 --> 00:12:59,640 We went over how to view different files, 242 00:12:59,640 --> 00:13:02,133 sort them out in alphabetical order, 243 00:13:03,030 --> 00:13:05,010 word count, of course getting information 244 00:13:05,010 --> 00:13:07,140 about the amount of lines in the text, 245 00:13:07,140 --> 00:13:10,740 the amount of characters, also the word count as well. 246 00:13:10,740 --> 00:13:13,677 We also went through how to search things with grep. 247 00:13:13,677 --> 00:13:18,540 And also, last but not least, symbolic versus hard linking. 248 00:13:18,540 --> 00:13:20,840 Thank you and I'll see you in the next lesson.