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Time Narration
0:00 ଲିନକ୍ସ ଫାଇଲ୍ ସିଷ୍ଟମ ବିଷୟରେ ଏହି ସ୍ପୋକେନ୍ ଟ୍ୟୁଟୋରିଆଲ କୁ ସ୍ବାଗତ.
0:04 I am using Ubuntu 10.04.
0:07 We assume that you know how to get started with the Linux operating system and have some basic idea about commands.
0:13 If you are interested, it is available through another spoken tutorial, on the following website
0:25 Also note that linux is case sensitive.
0:28 All the commands used in this tutorial are in lower case unless otherwise mentioned.
0:36 In Linux almost everything is a file.
0:39 So what is a file? In real life we know that a file is where we store our documents and papers.
0:47 Similarly in Linux a file is a container for storing information.
0:53 Next what is a directory?
0:56 A directory can be understood as a collection of files and other (sub)directories.
1:02 A directory helps us in organising our files in a systematic manner.
1:08 This is like what we call folders in Windows.
1:12 It allows different users to have their own directories with their files which others cannot access or modify.
1:20 Also if there are no directories, all the files on the system need to have unique names,which would be very difficult to maintain.
1:31 Though these definitions of files and directories are good to get a general feel about them, they are not entirely accurate.
1:42 As well as its contents, a file has a name and some properties, or “administrative information”; that is, the file’s creation/modification date and its permissions.
1:55 The properties are stored in the file’s inode, a special block of data in the file system that also contains the length of the file and where on the disk it’s stored.
2:08 The system uses the number of the file’s inode; the directory structure just names the file for our benefit as its easier for us to remember names than large numbers.
2:23 Contrary to its oversimplified definition, a directory doesnot actually store other files ,it is itself a file that holds the inode numbers and names of other files.
2:37 In fact in Linux there are three kinds of files:
2:41 1 Regular Files or Ordinary files: It contains only data , as a stream of characters.
2:48 2 Directories: As we just saw in the previous slides.
2:52 3 Device Files: All hardware devices and peripherals are represented as files in Linux.
2:59 A CD, a Harddisk or even an usb stick, everything is a file in Linux. But why is this so? This helps to read and write these devices in a way similar to that for ordinary files.
3:15 All files in Linux are related, in short all form a family much like we do.
3:22 A directory containing say some files and subdirectories will have a parent – child relationship with each other. This gives rise to the Linux File System Tree.
3:34 At the top is the root( denoted by a frontslash /). It contains all the other files and directories.
3:42 This also helps in easy navigation from one file or directory to other, if we know the correct path.
3:51 As we work with a Linux file system, it seems that we are moving along this tree.
3:56 One command and there you are teleported from one place to other.
4:01 Sounds interesting!! Indeed it is. As we will see.
4:05 When we login into the Linux system we are by default in a home directory.
4:11 Now Switch to the terminal.
4:13 Ctrl+alt+T helps to start a terminal in Ubuntu.
4:17 This command may not work in all unix systems, however. A general procedure to open a terminal is already explained in another spoken tutorial.
4:27 To see the home directory , Type at the command prompt

"echo space dollar H-O-M-E in capital" and press enter.

4:40 This gives the pathname of our home directory.
4:44 We can move around from one directory to other.
4:47 But any time we can be in one directory and this directory is known as the current directory or working directory. Now go back to slides.
4:56 The pwd command helps us to see the current directory. pwd stands for present working directory.
5:03 Type at the command prompt "pwd" and press enter. Now this is our present working directory.
5:13 We have said that we can move from one directory to other.
5:17 But how do we do so? We have the cd command for this purpose.
5:22 You have to type the command cd followed by the pathname of the directory you want to move to.
5:28 Lets again see our current directory by typing pwd at the command prompt and press enter.
5:37 So, now we are placed in this directory.
5:41 Now say we want to move to slash usr directory. So, type

"cd space slash usr" . Remember here slash in linux means front slash and press enter.

5:56 Now lets see our current directory. Type pwd and press enter.
6:03 Yes we have moved to slash usr directory.
6:08 The problem here is the pathnames can be very long, this is because these are Absolute Pathnames that enlist the entire path staring from the root directory.
6:18 Instead we may use Relative pathnames that begin from the current directory.
6:23 Here we need to know two special characters.

dot that represent the current directory and dot dot that represent the parent directory of the current directory.

6:36 Now let us have a brief session on cd command
6:40 The command cd without any argument is used to move back to the home directory.
6:46 Type at the command prompt "cd" and press enter.
6:51 Now check our current directory by the pwd command.
6:55 So, now we are back in our home directory

/home/gnuhata [ narration- slash home slash gnuhata ]

7:01 Now let us move to music directory. Type at the command prompt "cd space Music(M in capital) slash" and press enter
7:13 Now check our current directory by the pwd command. pwd and press enter. See, we have moved /home/gnuhata/Music
7:26 Let us go to the parent directory from Music. For that you have to use cd command with dot dot.
7:33 Type at the command prompt cd space dot dot and press enter.
7:40 Now check our present directory by typing pwd. We are again in /home/gnuhata
7:51 Now lets try to move to a subdirectory of the current directory using dot.
7:58 Type at the command prompt cd space dot slash Documents(D in capital) slash. Press enter.
8:09 Check our current directory by typing pwd. We are at /home/gnuhata/Documents
8:19 Let me clear the screen by pressing control L. So you can see clearly.
8:23 To go back to our home directory by cd command.

Type cd and press enter.

8:32 Again check our current directory by pwd command. We are back to /home/gnuhata .
8:41 We can combine any number of .. [narration - dot dot] separated by / [narration- slash] in a relative path .
8:47 In this slide, we can see the file system hierarchy. Root or / is at the top. home and bin are two sub-directories under root. username , here the directory named gnuhata is a sub-directory under home.
9:05 So, now we are in /home/gnuhata. Now how can we go to the bin directory?
9:12 Type at the command prompt

"cd space dot dot slash dot dot slash bin" and press enter.

9:23 Check our current directory by the command pwd.

We are at /bin [narration - slash bin]

9:30 The first .. [narration-dot dot] takes us from /home/gnuhata [narration - slash home slash gnuhata] to /home [narration - slash home] . |- | 9:37 |The next takes us from /home to root.
9:43 Now from / or root, we have moved to /bin directory.
9:48 Go back to our home directory by the command cd.
9:52 To create a directory we use the mkdir command.
9:56 You have to type the command and name of directory to be created and a directory would be created under the current directory.
10:04 To create a directory named testdir, type the command "mkdir space testdir" and press enter.
10:15 This creates the testdir directory successfully.
10:19 Note that, there is no explicit notification of successful directory creation or removal.
10:25 If you do not get any error message, it denotes successful execution.
10:30 We can also use the relative or absolute pathname to create a directory anywhere in the tree provided we have the permission to do so and a directory by that name does not already exist.
10:43 This process can be used for making multiple directories or even a hierarchy of directories.
10:49 Type "mkdir space test1 space test2 and press enter ,this will make two directories named test1 and test2 under the present directory.
11:06 Type "mkdir space testtree space testtree slash test3".
11:20 This will make a directory testtree and another directory test3 which is a sub-directory under testtree.
11:28 So, we have created four directories namely testdir,test1,test2 and testtree in the current directory, out of which first three are empty and the last one contains a subdirectory namely test3.
11:47 Similar to mkdir is the rmdir command which is used for removing a directory or directories.
11:56 The command "rmdir space test1" removes the test1 directory successfully.
12:09 A directory can be removed only if you are its owner, your current directory is hierarchically above the directory to be removed and the directory is empty.
12:23 Now type at the command prompt

"cd space testtree slash test3"

12:35 So, we are now in test3 directory which is a subdirectory under testtree.
12:42 Lets try to remove the testdir directory by typing the command "rmdir space testdir". Press enter.
12:55 We see it can't be done, because the current directory is not hierarchically above the directory to be removed.
13:02 So,we have to go to the directory which is hierarchically above testdir directory.
13:08 Type "cd space dot dot" and press enter.
13:14 Now, go back to our parent directory by typing the command "cd space dot dot".
13:20 Now, again try the previous command.
13:24 Type "rmdir space testdir". Press enter.
13:30 The testdir directory is successfully deleted. Note that, testdir directory was also empty.
13:38 Multiple directories or a hierarchy of directories can be removed at once.So, try to delete the testtree directory along with its subdirectory test3.
13:48 Type at the command prompt

"rmdir space testtree space testtree slash test3 "press enter.

14:02 See, it is giving the error message that 'testree' directory cannot be removed because testtree is not empty.
14:11 But one thing which you may miss is that testtree/test3 has been deleted as it was empty.
14:19 To check that, type at the command prompt "cd space testtree" and press enter.
14:27 Now type "ls" and press enter. See, the directory contains nothing. So, test3 was deleted.
14:36 So in this linux tutorial we have learnt about Linux Files and directories and how to work with Linux Directories. See them, move between them, make them,remove them.
14:49 This brings me to the end of this tutorial. Spoken Tutorials are a part of the Talk to a Teacher project, supported by the National Mission on Education through ICT.
15:03 More information this is available at the following link
15:08 This script has been contributed by ----------------------(name of the translator) and this is -----------------------(name of the recorder) from --------------------------(name of the place)signing off . Thanks for joining.

Contributors and Content Editors

Devraj, Gaurav, Manoranjan, PoojaMoolya, Pradeep