BOSS-Linux/C2/File-Attributes/English-timed

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Time Narration
00:01 Welcome to this spoken tutorial on Linux File Attributes.
00:05 The prerequisite for this tutorial is to create empty files named as example1, example2, example3, example4, example5 and testchown.
00:18 Please create empty directories named as test_chown and directory1 also.
00:25 A file attribute is metadata that describes or is associated with a computer file.
00:34 File attribute is the characteristics that describe a file, such as owner, file type, access permissions, etc.
00:46 c-h own command is used to change the ownership of the file or directory. This is an admin command, root user only can change the owner of a file or directory.
01:01 The syntax of the chown command is: chown space options space ownername space filename or directoryname.
01:13 We may give the following options with chown command.
01:18 -R : To change the permission on files that are in the sub-directories of the directory that you are currently in.
01:28 -c : Change the permission for each file.
01:32 -f : Prevents ch own from displaying error messages.
01:37 Now, we will look at some examples.
01:41 So, go to the terminal. We will move to the directory where we have created empty files and folders. For that, cd space Desktop slash file attribute and press Enter.
01:56 Now type the command: ls space -l space testchown that is t-e-s-t-c-h-o-w-n and press Enter.
02:11 Here we can see the owner of the testchown is "shahid".
02:18 To change the owner of the file, type the command sudo space c-h own space a-n-u-s-h-a anusha space testchown that is t-e-s-t-c-h-o-w-n and press Enter.
02:36 Enter the sudo password and press Enter again. Press Enter.
02:44 Now type: ls space -l space t-e-s-t-c-h-o-w-n and press Enter. Here, we can see the new owner of the file is "anusha".
03:03 Now we will see how to change owner of the directory.
03:07 Type the command: ls space -l and press Enter. Here we can see the owner of the directory test_chown is "shahid".
03:22 To change the owner of the directory, type the command:
03:26 sudo space chown space minus capital R space a-n-u-s-h-a anusha space test_chown which is directory name and press Enter.
03:44 Enter the sudo password, if required, and press Enter again.
03:49 I will clear the screen by pressing Clt+L for our convenience. Now type: ls space -l and press Enter. Here we can see the new owner of the directory is "anusha".
04:06 chmod command is used to change the access mode or permissions of one or more files.
04:13 Syntax of the chmod command is: chmod space [options] space mode space filename

We may give the following options with the chmod command-

04:29 -c : Print information about files that are changed.
04:34 -f : Do not notify user of files that chmod cannot change.
04:41 There are following types of access or permissions-
04:44 r: that is Read

w: that is Write

x: that is Execute

s: that is Set user (or group) ID.

04:54 Alternatively, we may specify permissions by a three-digit octal-number.
05:00 The first digit stands for owner permission, the second stands for group permission and the third stands for other permission.
05:09 Permissions are calculated by adding the following octal values-

4: that is Read

2: that is Write

1: that is Execute.

05:20 Now we will look at some examples of chmod. Move to terminal and enter the command to add execute-by-user permission to file example1.
05:30 Before that I will again clear the screen by pressing Clt+l.
05:36 Now, let's type chmod space u+x space example1 press Enter.
05:49 Now, type: ls space -l space example1

press Enter to see the changes.

06:01 Here, you can see to assign the read/write/execute permission by owner, read/execute permission by group, and execute-only permission by others to file 'example1'.
06:15 Now type the command: chmod space 751 space example1 press Enter.
06:26 Now type: ls space -l space example1 and press Enter.
06:35 Here we can see that above command has assigned the read/write/execute permission by owner, read/execute permission by group and execute-only permission by others to file example1.
06:52 To assign read-only permission to file example1 for everyone, type the command: chmod space =r space example1 and press Enter.
07:08 Now type the command: ls space -l space example1 press Enter.
07:19 Here we can see that the read only permission has been assigned to file 'example1' for everyone.
07:30 To change the permission recursively and assign the read and execute access for everyone and also write access for the owner of the directory 'directory1', type the command:
07:44 chmod space minus capital R space 755 space directory1 press Enter.
08:00 Now type: ls space -l press Enter to see the changes.
08:09 To give the user execute permission on file 'example2', type the command:

chmod space u+x space example2 press Enter.

08:27 Now type the command: ls space -l space example2 and press Enter.
08:40 Here, we can see that execute permission has been assigned to user on 'example2'.
08:50 To add the write permissions to the group for file 'example3', type the command: chmod space g+w space example3. Press Enter.
09:10 And now, type: ls space -l space example3 press Enter.
09:24 Here we can see the write permission has been added to group.
09:30 To remove the write permissions for all, type the command: chmod space a-w space example3 press Enter.
09:45 Now type: ls space -l space example3 press Enter.
09:55 Here we can see the write permission for all has been removed.
10:02 chgrp command is used to change the group of one or more files to new group.
10:10 New group is either a group ID number or a group name located in /etc/group.
10:20 Only the owner of a file or a privileged user may change the group.
10:26 The syntax for the chgrp command is: chgrp space [options] space newgroup space files.
10:36 Let's go to terminal. Now we will look at some examples of chgrp command.

Type the command ls space -l space example4 press Enter.

10:57 Here we can see the group permission is for user "shahid".
11:03 To change the group permission, type the command: sudo space chgrp space rohit space example4.
11:20 Press Enter. Enter the 'sudo' password if required.
11:27 Now type the command: ls space -l space example4 . Press Enter.
11:38 Here we can see that the group has changed from "shahid" to "rohit".
11:46 The inode-number is a unique integer assigned to a device.
11:51 Inode stores basic information about a regular file or a directory.
11:57 All the files are hard-links to inodes.
12:00 Whenever a program refers to a file by name, the system actually uses the filename to search for the corresponding inode.
12:12 We can use ls space -i command to see the inode-number of a file.
12:19 Type the command: ls space -i space example5 press Enter.
12:29 Number written before the file is the inode-number of the file.
12:35 Inodes are associated with precisely one directory at a time.
12:41 Hard links are to associate multiple directory entries with a single inode. ln is the command to make link.
12:52 The syntax of ln command to create the hard link is:
12:57 ln space source space link where source is an existing file and link is the file to create.
13:06 Now we will look at some examples of hard-links.
13:10 Let me clear the screen again. Now type the command: ln space example1 space exampleln press Enter.
13:25 To display the inode number of both the files, type the command:

ls space -i space example1 space exampleln press Enter.

13:41 Here we can see that inode number of both the files are same; file 'exampleln' is the hard-link for file 'example1'.
13:54 Soft-link i.e. symbolic link is a special type of file that contains a reference to another file or directory in the form of an absolute or relative path.
14:07 The syntax of ln command to create soft links is:
14:12 ln space -s space {target-filename} space {symbolic-filename}.
14:19 Now we will look at some examples of soft-link.
14:25 To create the soft-link, type the command: ln space -s space example1 space examplesoft .
14:40 Press Enter.
14:43 Now, to display the inode number and list of both the files, type the command:

ls space -li space example1 space examplesoft.

15:01 Press Enter.
15:03 Here we can see that inode number of both the files are different and 'examplesoft' is a soft-link of 'example1'.
15:16 So, in this tutorial we have learnt about the Linux Files Attributes like changing permission, ownership and group of a file.
15:26 We also learnt about the inode, soft and hard-links of a file.
15:31 This brings me to the end of this tutorial.
15:35 Spoken Tutorials are a part of the "Talk to a Teacher" project, supported by the National Mission on Education through ICT.
15:44 More information on the same is available at the following link.
15:50 This script is contributed by Anusha Ambala and Shahid. Thanks or joining.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Pravin1389, Sandhya.np14