WEBVTT 00:00.690 --> 00:05.340 If you're going to have a modern operating system today you're going to have to have a file and folder 00:05.340 --> 00:06.140 permissions. 00:06.270 --> 00:09.110 And certainly Linux is no exception to that rule. 00:09.300 --> 00:15.360 So in this episode what I want to do is go through linux file and folder permissions and then show you 00:15.360 --> 00:16.910 how we can edit those. 00:16.920 --> 00:22.510 So the best way to get started with this is to die than go into a particular folder and just type LS 00:22.530 --> 00:24.930 minus L. 00:25.040 --> 00:31.250 So if you take a look here on the far left hand side we see all these letters and dashes and that's 00:31.250 --> 00:34.850 really where all the file permission magic takes place. 00:35.120 --> 00:40.550 As you look at this on the far left hand side you're going to see one that has the letter D. 00:40.550 --> 00:43.790 That means it's a directory so that very first value. 00:43.790 --> 00:48.800 I just want you to just ignore it for this episode that's just used to separate files from directories 00:48.800 --> 00:50.590 from links and other stuff like that. 00:50.600 --> 00:54.150 What's important are the next nine values. 00:54.200 --> 01:00.050 So if you take a look here you're going to see individual files have ours and W's and X's and dashes 01:00.050 --> 01:02.910 in different places depending on what's happening here. 01:02.930 --> 01:05.270 Those are the file and folder permissions. 01:05.270 --> 01:09.490 Now to get started on this I want to explain to you how they're organized. 01:09.530 --> 01:13.700 And I'm going to have to wait just a minute then I'm going to tell you what our you x means so bear 01:13.700 --> 01:15.210 with me. 01:15.590 --> 01:18.550 You have three groups of these R.W. exes. 01:18.590 --> 01:24.260 So if we zero in for example down in this bottom five right here called Run me you'll see I have r w 01:24.260 --> 01:26.750 x R W x R W x. 01:26.750 --> 01:32.120 What you're looking at here are three different permissions depending on the entity that you want to 01:32.120 --> 01:33.710 apply permissions to. 01:33.980 --> 01:39.320 The first three values are the permissions that are applied to the creator owner whoever created that 01:39.320 --> 01:44.030 file whoever created that directory usually has very powerful permissions on it. 01:44.090 --> 01:47.390 And that's what the creator owner can do. 01:47.390 --> 01:54.860 The second set in the middle there is for the group every file and folder in a Linux system belongs 01:54.860 --> 01:58.610 to a group and other users can be in that group. 01:58.730 --> 02:03.740 And you can define the permissions for everybody in that group for that particular file or folder simply 02:03.740 --> 02:07.110 by editing those three letters right there. 02:07.700 --> 02:13.730 Now if you're not the creator owner and if you're not in the group well then what permissions do you 02:13.730 --> 02:14.170 get. 02:14.240 --> 02:16.220 And that's what that third set is for. 02:16.220 --> 02:19.940 The third set defines permissions for everybody else. 02:19.940 --> 02:23.670 The rest of the world the universe whatever you might want to look at that as. 02:23.780 --> 02:28.060 So we break it up into these three very distinct groups. 02:28.420 --> 02:31.180 OK now let's go back in. 02:31.220 --> 02:38.180 Except this time I want to take a moment and talk about what exactly are and W and X mean it's going 02:38.180 --> 02:43.040 to vary depending on whether these permissions are applied to a file or to a directory. 02:43.280 --> 02:49.730 R stands for read a readable permission allows the contents of a file to be viewed in other words you 02:49.730 --> 02:57.440 can open a file read permission on a directory allows you to list the contents of that directory right. 02:57.440 --> 03:04.040 Permission allows you to modify the contents of a file but the right permission for a directory allows 03:04.040 --> 03:08.480 you to edit the contents of that directory which is a nice way of saying you can add or delete files 03:08.480 --> 03:10.450 from that particular directory. 03:11.440 --> 03:14.890 Executes a little bit strange for a file it makes sense. 03:14.890 --> 03:21.070 The executable permission allows you to run the file and execute a program or a script for a directory 03:21.070 --> 03:26.620 though the execute permission allows you to change to a different directory and make it your current 03:26.620 --> 03:27.970 working directory. 03:27.970 --> 03:32.860 So if you want to get out of a particular directory and go someplace else make sure it's executable 03:33.040 --> 03:37.270 for your particular user owner group or other. 03:37.440 --> 03:43.120 The tool we use in Linux to change file and folder permissions is called chmod. 03:43.240 --> 03:47.560 Now chmod is an interesting command and there's a couple of different ways to run it. 03:47.560 --> 03:50.210 And since I don't know how come t is going to tell you how to do it. 03:50.230 --> 03:51.880 We're going to try it both ways. 03:51.890 --> 03:57.310 So first of all what we're going to do is we're going to use chmod to change some permissions on one 03:57.310 --> 04:01.120 particular file a little executable program called Run me. 04:01.120 --> 04:06.430 Now run me is a very dangerous program so I want to be very specific about who can actually run this 04:06.430 --> 04:07.930 particular program. 04:07.960 --> 04:14.430 So I've got my Ls minus l running and you can see right now anybody can execute this program and see 04:14.430 --> 04:15.580 all three x's. 04:15.580 --> 04:19.920 So the creator owner the group and the others can all run this. 04:19.930 --> 04:26.440 So the first thing I am going to do tomorrow is I want to give the other people no rights to do anything 04:26.440 --> 04:32.680 on this thing so to do that I'm going to type in chmod and now I'm going to start typing in some switches. 04:32.680 --> 04:38.830 The switches here are either are going to be a letter followed by an equal sign and then the permissions 04:38.830 --> 04:39.160 I want. 04:39.160 --> 04:45.130 So in this particular case I'm going to say over other equals and I'm going to leave it blank which 04:45.130 --> 04:48.730 means turn off all permissions for the other people. 04:48.880 --> 04:51.880 And then obviously I'm going to type in the name of the file. 04:52.150 --> 05:01.700 So I run this and now you can see if you take a close look you'll see that the other group has absolutely 05:01.760 --> 05:06.770 no rights to this is somebody who isn't the creator owner or member of the group tries to execute this 05:06.770 --> 05:07.360 program. 05:07.430 --> 05:08.230 It's not going to happen. 05:08.240 --> 05:10.460 They don't have permissions. 05:10.460 --> 05:15.360 Now the other thing I want to do is I want to take a look and we can see the group has read right next. 05:15.360 --> 05:18.640 Q permissions since it's really just an executable file. 05:18.710 --> 05:20.450 There's really no reason to write to it. 05:20.450 --> 05:25.310 So what I'm going to do in this case is I'm going to turn off right permissions for the group. 05:25.430 --> 05:33.770 So again I type in chmod and now this time I type G for group and here all I want them to have is read 05:33.770 --> 05:35.430 and execute permissions. 05:35.600 --> 05:44.030 And then once again typing in the name of the file so I typed LS minus ELP and you can see that I've 05:44.030 --> 05:48.530 got rid of the right permissions so you can do a lot of cool stuff with this. 05:48.530 --> 05:52.990 Now there's one more chmod type command I want to show you in this version to run. 05:53.090 --> 05:57.410 And that means when you want to do it to everybody let's just say I'm feeling crazy and I want to give 05:57.470 --> 05:59.940 everybody rights to do everything they want to do. 06:00.080 --> 06:04.270 So in that case I'm going to run chmod and I'm going to use a. 06:04.280 --> 06:13.300 That means everybody creator owner group and other and easy I'm typing in a equals R W X so that means 06:13.300 --> 06:17.830 give everybody all the permissions run make 06:21.360 --> 06:21.960 me type. 06:21.970 --> 06:29.040 LS might well and you can see that I've put back all of the missions for that particular one. 06:29.590 --> 06:31.920 So that's one way to run Tramon. 06:32.020 --> 06:36.580 Now there is a whole other way to run it which is a little bit more old school and guys like me like 06:36.580 --> 06:37.380 to use. 06:37.480 --> 06:44.860 So I want to run Chimay one more time but this time what we're going to do is we're going to use numbers 06:44.920 --> 06:47.200 instead of letters to change things. 06:47.260 --> 06:54.400 Now in order for you to understand these numbers keep in mind that we have three values read write and 06:54.460 --> 06:55.510 execute. 06:55.510 --> 06:59.540 So in a binary world the read is in a four position. 06:59.710 --> 07:05.270 The right is in a two position and the execute is in a one position. 07:05.410 --> 07:12.040 So to explain that a little bit better let me put a little graphic up so that you can correlate the 07:12.040 --> 07:15.700 positions of those three values to binary values. 07:15.700 --> 07:18.040 Take a look at this. 07:18.250 --> 07:26.620 So we know that every linux file has read write and execute permissions for the creator owner the group 07:26.890 --> 07:28.600 and then the rest of the world. 07:28.600 --> 07:32.860 Now we've seen chmod used one way but let me show you this other way. 07:32.860 --> 07:38.200 So first thing I want to do is let's just pick on any one of these three so we'll just pick this one 07:38.200 --> 07:39.730 that's as good as anting. 07:39.980 --> 07:46.640 Now we understand that setting a permission basically turns it on or off. 07:46.660 --> 07:52.840 So there is kind of a binary thing to this if you think about this for a minute like for example we 07:52.840 --> 07:57.940 could turn off the read permission we could turn off the right permission and just turn on the execute 07:57.940 --> 07:58.990 permission. 07:58.990 --> 08:06.940 Equally we could turn on the read and the right permission and turn on the exit turn off the execute 08:06.940 --> 08:15.250 permission or we could turn on all of these permissions so really what you've got is three binary digits 08:15.850 --> 08:21.790 that we can convert to decimal Let's go ahead and go through all this real quick so all zeros and binary 08:21.790 --> 08:30.960 equals zero in decimal 0 0 1 equals 1 in decimal 0 1 0 equals 2 in decimal 0 1 1 equals 3. 08:30.960 --> 08:32.620 Here I'll just keep going through the rest of these. 08:32.620 --> 08:35.010 I think you can figure this out. 08:35.020 --> 08:43.600 So basically three binary values can have 1 2 3 4 5 6 7 8 different combinations going from zero to 08:43.600 --> 08:44.880 7 in decimal. 08:44.980 --> 08:49.630 And understanding that we can actually do something really cool with Jamaah to make our lives a lot 08:49.630 --> 08:50.470 easier. 08:50.470 --> 08:59.770 So for example on this particular one if we just want to set this particular one to read only all we 08:59.770 --> 09:03.310 have to do is type in 1 0 0 which is going to equal 4. 09:03.310 --> 09:12.890 So in essence we just say for if we want to set it to just write permission we would say to and if we 09:12.890 --> 09:15.750 want to say execute permission we say one. 09:15.770 --> 09:21.730 So really what it boils down to when you look at read write execute read gets the value of for right 09:21.740 --> 09:25.880 gets the value of two and execute gets the value of one. 09:26.000 --> 09:30.260 And we can use this combination which Hamada do cool things for example. 09:30.290 --> 09:35.730 So if I wanted to set the read permission I would just say four and that would turn off right and execute 09:36.140 --> 09:37.810 if I want to just the right permission. 09:37.820 --> 09:43.370 I would say to if I want to just execute permission I would say 1 but it also works for combinations 09:43.730 --> 09:47.300 if I want the read and right combination it will be a 6. 09:47.390 --> 09:52.920 And if I want everything it's going to be a 7 and we can use that to work with chmod. 09:53.300 --> 09:56.390 So let's go through one quick example of this. 09:56.390 --> 10:00.770 Now keep in mind we have three read write and executes to deal with not just one. 10:00.770 --> 10:09.740 So if I wanted to for example set everybody to read write and execute I would type chmod 7 7 7 and that 10:09.740 --> 10:12.640 would give everybody read right next cue permissions. 10:12.740 --> 10:18.800 But then again if I wanted to give the creator owner complete permission and then I wanted to give the 10:18.800 --> 10:20.810 group just read and write permission. 10:20.930 --> 10:30.980 And then if I wanted to give everybody else no permission at all that would be 7 6 0 OK. 10:31.620 --> 10:36.330 Now that you have a least rough idea of how this works what we're going to do is we're going to use 10:36.330 --> 10:39.820 Tamada again except this time we're just going to use numbers now. 10:39.930 --> 10:44.610 The downside of using Shimada like this is that you've got to be really really comfortable with binary 10:44.610 --> 10:48.240 and well luckily I am but you may not be so. 10:48.270 --> 10:53.580 If there's one thing you might want to rehearse a little bit are using these number of days for Chameides 10:53.610 --> 10:57.810 as opposed to what I think is the well now easier way of just using the letters. 10:57.810 --> 10:59.520 Anyway let's go through an example. 11:00.700 --> 11:04.420 If you take a look up on the screen you'll see that I have this run me right now. 11:04.420 --> 11:11.220 So I'm going to type chmod and I'm going to type in the number 7. 11:11.220 --> 11:14.580 Now think about this for a minute four plus two plus one equals seven. 11:14.580 --> 11:21.210 So if I give a value of seven that means I want read and write and execute the order that I put these 11:21.210 --> 11:24.910 numbers in depends on whether it's for the creator owner the group or other. 11:24.900 --> 11:30.670 So the first value seven means makes your creator owner has read write and execute. 11:30.690 --> 11:32.940 Now it's often common to do the same thing. 11:32.970 --> 11:38.350 So I'm going to type in a second seven so that the group has read write and execute permissions that 11:38.360 --> 11:41.160 the third one I'm going to do is I'm going to put in the number five. 11:41.160 --> 11:45.270 Now with the number five in there now I'm really speculate for a minute. 11:45.630 --> 11:48.660 What permission am I turning off by doing that. 11:48.660 --> 11:49.660 I'll give you a clue. 11:49.710 --> 11:52.660 Seven minus two equals five. 11:52.800 --> 11:55.400 So let's go ahead and run this. 11:55.470 --> 12:01.060 They can see I type chmod and a number and then the actual file that I want to change I hit enter. 12:01.080 --> 12:06.660 Now if I type LS minus L right now if I've done it right there it is. 12:06.660 --> 12:10.020 The w is not in for other. 12:10.020 --> 12:15.530 So what I did by typing a five in that third position as I said turn off right. 12:15.540 --> 12:19.380 Permission for that particular file. 12:19.410 --> 12:21.360 So which my you can have a lot of fun. 12:21.360 --> 12:25.260 In fact you'll see people with Jamaah they'll say chmod 777. 12:25.260 --> 12:27.740 And what they're saying is just turn everything on. 12:28.010 --> 12:28.490 OK. 12:28.530 --> 12:29.440 Now that's Tramon. 12:29.460 --> 12:30.690 So Juds pretty cool. 12:30.730 --> 12:31.780 And I like it. 12:31.860 --> 12:39.660 But what I want to do now is go from dealing with who has what type of file and folder permissions to 12:39.780 --> 12:41.790 who owns a particular file. 12:41.790 --> 12:44.530 And to do that we're going to use tcha own. 12:44.670 --> 12:45.630 OK. 12:45.800 --> 12:48.710 So CHONE simply allows us to change ownership. 12:48.720 --> 12:49.830 Let me show you how that works. 12:49.860 --> 12:57.210 If you take a look at my Ls minus L here you'll see that right now the file run me has student as the 12:57.210 --> 12:57.480 owner. 12:57.480 --> 13:01.160 And what we're going to do right now is we're going to change that to route. 13:01.170 --> 13:04.400 So Joe needs sudo in order to work. 13:04.400 --> 13:10.230 So we're going to type sudo shown and we're going to type in truly want to change ownership to and then 13:10.230 --> 13:12.930 we type in the name of the file. 13:14.340 --> 13:20.040 Now look very carefully here you can see that the owner is now root. 13:20.070 --> 13:22.100 And that's what CHONE is all about. 13:22.110 --> 13:28.290 It's a quick way for you to be able to change the owner of a particular file or folder. 13:28.290 --> 13:28.610 All right. 13:28.620 --> 13:35.880 So we've messed with our file and folder permissions we have changed the ownership. 13:35.880 --> 13:42.000 Now the last thing I want to talk about is changing a password and to do that we use the S S W D command. 13:42.000 --> 13:47.860 Now again this one needs sudo so I'm going to type in pseudo SSW D. 13:47.970 --> 13:52.560 Now right now if I just hit enter it's going to change the password for the account I'm logged in on 13:52.560 --> 13:53.940 currently which is student. 13:54.030 --> 13:55.470 So I'm going to do that. 13:55.950 --> 13:57.930 So I'm going to enter a new Unix password 14:02.840 --> 14:05.980 and I have now changed the password successfully. 14:05.980 --> 14:11.280 So if you need to change a password make sure you know how to use p s s w d. 14:12.230 --> 14:15.000 On the plus objectives they do something very strange here. 14:15.150 --> 14:22.410 They actually in the objectives they put ph s s w d which is change passwords right with the command 14:22.410 --> 14:26.770 P W D which means for just show me the current working directory. 14:26.850 --> 14:31.350 I'm not quite sure why Campania does that but it might be a clue on something you're going to see on 14:31.350 --> 14:35.270 the exam on 14:37.910 --> 14:41.300 in 14:45.520 --> 14:49.090 an.