Difference between revisions of "BOSS-Linux/C2/File-System/English-timed"

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|-
 
|-
 
| 00:04
 
| 00:04
−
|I am using Ubuntu 10.04.  
+
|I am using Linux Operating system.
 
|-
 
|-
−
| 00:07
+
| 00:08
 
|We assume that you know how to get started with the Linux operating system and have some basic idea about commands.  
 
|We assume that you know how to get started with the Linux operating system and have some basic idea about commands.  
 
|-
 
|-
−
| 00:13
+
| 00:16
 
|If you are interested, it is available through another spoken tutorial, on the following website http://spoken-tutorial.org
 
|If you are interested, it is available through another spoken tutorial, on the following website http://spoken-tutorial.org
 
|-
 
|-
−
| 00:25
+
| 00:28
 
|Also note that linux is case sensitive.
 
|Also note that linux is case sensitive.
 
|-
 
|-
−
| 00:28
+
| 00:32
 
| All the commands used in this tutorial are in lower case unless otherwise mentioned.  
 
| All the commands used in this tutorial are in lower case unless otherwise mentioned.  
 
|-
 
|-
−
| 00:36
+
| 00:41
 
|In Linux almost everything is a file.  
 
|In Linux almost everything is a file.  
 
|-
 
|-
−
| 00:39
+
| 00:44
 
|So what is a file? In real life we know that a file is where we store our documents and papers.  
 
|So what is a file? In real life we know that a file is where we store our documents and papers.  
 
|-
 
|-
−
| 00:47
+
| 00:54
 
|Similarly in Linux a file is a container for storing information.  
 
|Similarly in Linux a file is a container for storing information.  
 
|-
 
|-
−
| 00:53
+
| 01:00
 
|Next what is a directory?  
 
|Next what is a directory?  
 
|-
 
|-
−
| 00:56
+
| 01:03
 
|A directory can be understood as a collection of files and other (sub)directories.
 
|A directory can be understood as a collection of files and other (sub)directories.
 
|-
 
|-
−
| 01:02
+
| 01:10
 
|A directory helps us in organising our files in a systematic manner.  
 
|A directory helps us in organising our files in a systematic manner.  
 
|-
 
|-
−
| 01:08
+
| 01:16
 
|This is like what we call folders in Windows.
 
|This is like what we call folders in Windows.
 
|-
 
|-
−
| 01:12
+
| 01:20
 
| It allows different users to have their own directories with their files which others cannot access or modify.  
 
| It allows different users to have their own directories with their files which others cannot access or modify.  
 
|-
 
|-
−
| 01:20
+
| 01:30
 
|Also if there are no directories, all the files on the system need to have unique names,which would be very difficult to maintain.
 
|Also if there are no directories, all the files on the system need to have unique names,which would be very difficult to maintain.
 
|-
 
|-
−
| 01:31
+
| 01:41
−
|Though these definitions of files and directories are good to get a general feel about them, they are not entirely accurate.  
+
|These definitions of files and directories are good to get a general feel about them, they are not entirely accurate.  
 
|-
 
|-
−
| 01:42
+
| 01:51
 
|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.  
 
|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.  
 
|-
 
|-
−
| 01:55
+
| 02:05
−
|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.  
+
|Thus  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.  
 
|-
 
|-
−
| 02:08
+
| 02:20
−
|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.
+
|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 larger numbers.
 
|-
 
|-
−
|02:23
+
|02:35
 
|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.  
 
|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.  
 
|-
 
|-
−
| 02:37
+
| 02:49
 
|In fact in Linux there are three kinds of files:
 
|In fact in Linux there are three kinds of files:
 
|-
 
|-
−
| 02:41
+
| 02:54
−
|1 Regular Files or Ordinary files: It contains only data , as a stream of characters.
+
|Regular Files or Ordinary files: It contains only data , as a stream of characters.
 
|-
 
|-
−
| 02:48
+
| 03:01
−
|2 Directories: As we just saw in the previous slides.
+
|Directories: As we just saw in the previous slides.
 
|-
 
|-
−
| 02:52
+
| 03:07
−
|3 Device Files: All hardware devices and peripherals are represented as files in Linux.  
+
|Device Files: All hardware devices and peripherals are represented as files in Linux.  
 
|-
 
|-
−
| 02:59
+
| 03:14
 
|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.
 
|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.
 
|-
 
|-
−
| 03:15
+
| 03:32
 
|All files in Linux are related, in short all form a family much like we do.  
 
|All files in Linux are related, in short all form a family much like we do.  
 
|-
 
|-
−
| 03:22
+
| 03:39
 
|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.
 
|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.
 
|-
 
|-
−
| 03:34
+
| 03:52
 
|At the top is the root( denoted by a frontslash /). It contains all the other files and directories.  
 
|At the top is the root( denoted by a frontslash /). It contains all the other files and directories.  
 
|-
 
|-
−
| 03:42
+
| 04:04
 
|This also helps in easy navigation from one file or directory to other, if we know the correct path.  
 
|This also helps in easy navigation from one file or directory to other, if we know the correct path.  
 
|-
 
|-
−
| 03:51
+
| 04:12
 
|As we work with a Linux file system, it seems that we are moving along this tree.  
 
|As we work with a Linux file system, it seems that we are moving along this tree.  
 
|-
 
|-
−
| 03:56
+
| 04:18
 
|One command and there you are teleported from one place to other.
 
|One command and there you are teleported from one place to other.
 
|-
 
|-
−
| 04:01
+
| 04:24
 
|Sounds interesting!! Indeed it is. As we will see.
 
|Sounds interesting!! Indeed it is. As we will see.
 
|-
 
|-
−
| 04:05
+
| 04:29
 
|When we login into the Linux system we are by default in a home directory.  
 
|When we login into the Linux system we are by default in a home directory.  
 
|-
 
|-
−
| 04:11
+
| 04:36
 
|Now Switch to the terminal.
 
|Now Switch to the terminal.
 +
 
|-
 
|-
−
| 04:13
+
| 04:39
−
| Ctrl+alt+T helps to start a terminal in Ubuntu.
+
|To see the home directory , Type at the command prompt "'echo space dollar H-O-M-E in capital"' and press enter.
−
|-
+
−
| 04:17
+
−
|This command may not work in all unix systems, however. A general procedure to open a terminal is already explained in another spoken tutorial.
+
−
|-
+
−
| 04:27
+
−
|To see the home directory , Type at the command prompt
+
−
"echo space dollar H-O-M-E in capital" and press enter.
+
 
|-
 
|-
−
| 04:40
+
| 04:53
−
|This gives the pathname of our home directory.  
+
|This gives the pathname of our '''home''' directory.  
 
|-
 
|-
−
| 04:44
+
| 04:57
 
|We can move around from one directory to other.  
 
|We can move around from one directory to other.  
 
|-
 
|-
−
| 04:47
+
| 05:01
−
|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.
+
|But any time we can be in one directory and this directory is known as the current directory or working directory.  
 
|-
 
|-
−
| 04:56
+
| 05:09
−
|The pwd command helps us to see the current directory. pwd stands for present working directory.
+
|The '''pwd''' command helps us to see the current directory. '''pwd''' stands for present working directory.
 
|-
 
|-
−
| 05:03
+
| 05:18
−
|Type at the command prompt "pwd" and press enter. Now this is our present working directory.  
+
|Type at the command prompt '"pwd'" and press enter. Now this is our present working directory.  
 
|-
 
|-
−
| 05:13
+
| 05:28
 
|We have said that we can move from one directory to other.  
 
|We have said that we can move from one directory to other.  
 
|-
 
|-
−
| 05:17
+
| 05:32
−
|But how do we do so? We have the cd command for this purpose.
+
|But how do we do so? We have the '''cd''' command for this purpose.
 
|-
 
|-
−
| 05:22
+
| 05:39
−
|You have to type the command cd followed by the pathname of the directory you want to move to.
+
|You have to type the command '''cd''' followed by the pathname of the directory you want to move to.
 
|-
 
|-
−
| 05:28
+
| 05:47
−
|Lets again see our current directory by typing pwd at the command prompt and press enter.
+
|Lets again see our current directory by typing '''pwd''' at the command prompt and press enter.
 
|-
 
|-
−
|05:37
+
|05:57
 
| So, now we are placed in this directory.
 
| So, now we are placed in this directory.
 
|-
 
|-
−
| 05:41
+
| 06:01
−
|Now say we want to move to slash usr directory. So, type  
+
|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.
−
"cd space slash usr" . Remember here slash in linux means front slash and press enter.
+
 
|-
 
|-
−
| 05:56
+
| 06:17
−
|Now lets see our current directory. Type pwd and press enter.
+
|Now lets see our current directory. Type '''pwd''' and press enter.
 
|-
 
|-
−
| 06:03
+
| 06:24
−
|Yes we have moved to slash usr directory.  
+
|Yes we have moved to '''slash usr''' directory.  
 
|-
 
|-
−
| 06:08
+
| 06:30
 
|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.
 
|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.
 
|-
 
|-
−
| 06:18
+
| 06:42
 
|Instead we may use Relative pathnames that begin from the current directory.  
 
|Instead we may use Relative pathnames that begin from the current directory.  
 
|-
 
|-
−
| 06:23
+
| 06:48
−
|Here we need to know two special characters.
+
|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.  
−
'''dot''' that represent the current directory and '''dot dot''' that represent the parent directory of the current directory.  
+
 
|-
 
|-
−
| 06:36
+
| 07:02
−
|Now let us have a brief session on cd command
+
|Now let us have a brief session on '''cd''' command
 
|-
 
|-
−
| 06:40
+
| 07:06
−
|The command cd without any argument is used to move back to the home directory.  
+
|The command '''cd''' without any argument is used to move back that to the home directory.  
 
|-
 
|-
−
| 06:46
+
| 07:13
−
|Type at the command prompt "cd" and press enter.  
+
|Type at the command prompt "'cd'" and press enter.  
 
|-
 
|-
−
| 06:51
+
| 07:19
−
|Now check our current directory by the pwd command.  
+
|Now check our current directory by the '''pwd''' command.  
 
|-
 
|-
−
| 06:55
+
| 07:23
−
|So, now we are back in our home directory
+
|So, now we are back in our home directory '''/home/gnuhata''' [ slash home slash gnuhata ]  
−
<nowiki>/home/gnuhata [ narration- slash home slash gnuhata ] </nowiki>
+
 
 
|-
 
|-
−
| 07:01
+
| 07:30
−
|Now let us move to music directory. Type at the command prompt "cd space Music(M in capital) slash" and press enter
+
|Now let us move to music directory. Type at the command prompt "'cd space Music(M in capital) slash"' and press enter
 
|-
 
|-
−
| 07:13
+
| 07:43
−
|Now check our current directory by the pwd command. pwd and press enter. See, we have moved /home/gnuhata/Music  
+
|Now check our current directory by the '''pwd''' command. '''pwd''' and press enter. See, we have moved ''' /home/gnuhata/Music '''
 
|-
 
|-
−
| 07:26
+
| 07:57
−
|Let us go to the parent directory from Music. For that you have to use cd command with dot dot.  
+
|Let us go to the parent directory of Music. For that you have to use cd command with dot dot.  
 
|-
 
|-
−
| 07:33
+
| 08:04
−
|Type at the command prompt cd space dot dot and press enter.  
+
|Type at the command prompt '''cd space dot dot''' and press enter.  
 
|-
 
|-
−
| 07:40
+
| 08:11
−
|Now check our present directory by typing pwd. We are again in /home/gnuhata
+
|Now check our present directory by typing '''pwd.''' We are again in '''/home/gnuhata'''
 
|-
 
|-
−
| 07:51
+
| 08:23
 
|Now lets try to move to a subdirectory of the current directory using dot.  
 
|Now lets try to move to a subdirectory of the current directory using dot.  
 
|-
 
|-
−
| 07:58
+
| 08:30
−
|Type at the command prompt cd space dot slash Documents(D in capital) slash. Press enter.
+
|Type at the command prompt '''cd space dot slash Documents(D in capital) slash'''. Press enter.
 
|-
 
|-
−
| 08:09
+
| 08:42
−
|Check our current directory by typing pwd. We are at /home/gnuhata/Documents
+
|Check our current directory by typing '''pwd.''' We are at ''' /home/gnuhata/Documents'''
 
|-
 
|-
−
| 08:19
+
| 08:53
 
|Let me clear the screen by pressing control L. So you can see clearly.
 
|Let me clear the screen by pressing control L. So you can see clearly.
 
|-
 
|-
−
| 08:23
+
| 08:58
−
|To go back to our home directory by cd command.
+
|To go back to our home directory by '''cd''' command. Type '''cd''' and press enter.
−
Type cd and press enter.
+
 
|-
 
|-
−
| 08:32
+
| 09:07
−
|Again check our current directory by pwd command. We are back to /home/gnuhata .  
+
|Again check our current directory by '''pwd''' command. We are back to '''/home/gnuhata''' .  
 
|-
 
|-
−
| 08:41
+
| 09:17
−
|<nowiki>We can combine any number of .. [narration - dot dot] separated by / [narration- slash] in a relative path . </nowiki>
+
|We can combine any number of dot dot separated by slash in a relative path .  
 
|-
 
|-
−
| 08:47
+
| 09:23
−
|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.
+
|In this slide, we can see the file system hierarchy. '''Root''' or '''slash''' 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.'''
 
|-
 
|-
−
| 09:05
+
| 09:43
−
| So, now we are in /home/gnuhata. Now how can we go to the bin directory?  
+
| So, now we are in '''/home/gnuhata.''' Now how can we go to the bin directory?  
 
|-
 
|-
−
| 09:12
+
| 09:51
−
|Type at the command prompt
+
|Type at the command prompt "'cd space dot dot slash dot dot slash bin'" and press enter.  
−
"cd space dot dot slash dot dot slash bin" and press enter.  
+
 
 
|-
 
|-
−
| 09:23
+
| 10:03
−
|Check our current directory by the command pwd.  
+
|Check our current directory by the command '''pwd.'''  We are at /bin (slash bin)
−
<nowiki>We are at /bin [narration - slash bin] </nowiki>
+
 
 
|-
 
|-
−
| 09:30
+
| 10:11
−
|<nowiki>The first .. [narration-dot dot] takes us from /home/gnuhata [narration - slash home slash gnuhata] to /home [narration - slash home].</nowiki>
+
|The first .. (dot dot) takes us from /home/gnuhata (slash home slash gnuhata) to /home (slash home)
  
 
|-
 
|-
−
| 09:37
+
| 10:18
−
|<nowiki>The next takes us from /home to </nowiki>root.  
+
|The next takes us from '''slash home''' to root.  
 
|-
 
|-
−
| 09:43
+
| 10:24
−
|Now from / or root, we have moved to /bin directory.
+
|Now from root or slash, we have moved to /bin directory.
 
|-
 
|-
−
| 09:48
+
| 10:30
−
|Go back to our home directory by the command cd.  
+
|Go back to our home directory by the command '''cd.'''
 
|-
 
|-
−
| 09:52
+
| 10:34
−
|To create a directory we use the mkdir command.  
+
|To create a directory we use the '''mkdir''' command.  
  
 
|-
 
|-
−
| 09:56
+
| 10:40
 
|You have to type the command and name of directory to be created and a directory would be created under the current directory.
 
|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
+
| 10:49
−
|To create a directory named testdir, type the command "mkdir space testdir" and press enter.
+
|To create a directory named '''testdir''', type the command '"mkdir space testdir'" and press enter.
 
|-
 
|-
−
| 10:15
+
| 11:01
−
|This creates the testdir directory successfully.  
+
|This creates the '''testdir''' directory successfully.  
 
|-
 
|-
−
| 10:19
+
| 11:05
 
|Note that, there is no explicit notification of successful directory creation or removal.
 
|Note that, there is no explicit notification of successful directory creation or removal.
 
|-
 
|-
−
| 10:25
+
| 11:13
 
| If you do not get any error message, it denotes successful execution.  
 
| If you do not get any error message, it denotes successful execution.  
 
|-
 
|-
−
| 10:30
+
| 11:18
 
|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.
 
|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
+
| 11:33
 
|This process can be used for making multiple directories or even a hierarchy of directories.
 
|This process can be used for making multiple directories or even a hierarchy of directories.
 
|-
 
|-
−
| 10:49
+
| 11:39
−
|Type "mkdir space test1 space test2 and press enter ,this will make two directories named test1 and test2 under the present directory.
+
|Type "'mkdir space test1 space test2''' and press enter ,this will make two directories named '''test1''' and '''test2''' under the present directory.
 
|-
 
|-
−
| 11:06
+
| 11:57
−
|Type "mkdir space testtree space testtree slash test3".  
+
|Type "'mkdir space testtree space testtree slash test3'".  
 
|-
 
|-
−
| 11:20
+
| 12:11
−
|This will make a directory testtree and another directory test3 which is a sub-directory under testtree.  
+
|This will make a directory '''testtree''' and another directory '''test3''' which is a sub-directory under '''testtree.'''
 
|-
 
|-
−
| 11:28
+
| 12:20
−
|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.  
+
|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
+
| 12:40
−
|Similar to mkdir is the rmdir command which is used for removing a directory or directories.
+
|Similar to the '''mkdir''' is the '''rmdir''' command which is used for removing a directory or directories.
 
|-
 
|-
−
| 11:56
+
| 12:50
−
|The command "rmdir space test1" removes the test1 directory successfully.  
+
|The command "'rmdir space test1'" removes the '''test1''' directory successfully.  
 
|-
 
|-
−
| 12:09
+
| 13:00
 
|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.
 
|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
+
| 13:13
−
|Now type at the command prompt
+
|Now type at the command prompt '"cd space testtree slash test3"'
−
"cd space testtree slash test3"
+
 
|-
 
|-
−
| 12:35
+
| 13:25
−
|So, we are now in test3 directory which is a subdirectory under testtree.
+
|So, we are now in '''test3''' directory which is a subdirectory under '''testtree.'''
 
|-
 
|-
−
| 12:42
+
| 13:33
−
|Lets try to remove the testdir directory by typing the command "rmdir space testdir". Press enter.  
+
|Lets try to remove the '''testdir''' directory by typing the command '"rmdir space testdir'". Press enter.  
 
|-
 
|-
−
| 12:55
+
| 13:46
 
|We see it can't be done, because the current directory is not hierarchically above the directory to be removed.
 
|We see it can't be done, because the current directory is not hierarchically above the directory to be removed.
 
|-
 
|-
−
| 13:02
+
| 13:54
−
|So,we have to go to the directory which is hierarchically above testdir directory.  
+
|So,we have to go to the directory which is hierarchically above '''testdir''' directory.  
 
|-
 
|-
−
| 13:08
+
| 14:00
−
|Type "cd space dot dot" and press enter.  
+
|Type "'cd space dot dot"' and press enter.  
 
|-
 
|-
−
| 13:14
+
| 14:06
−
|Now, go back to our parent directory by typing the command "cd space dot dot".  
+
|Now, go back to our parent directory by typing the command "'cd space dot dot'".  
 
|-
 
|-
−
| 13:20
+
| 14:13
 
|Now, again try the previous command.  
 
|Now, again try the previous command.  
 
|-
 
|-
−
| 13:24
+
| 14:16
 
|Type "rmdir space testdir". Press enter.  
 
|Type "rmdir space testdir". Press enter.  
 
|-
 
|-
−
| 13:30
+
| 14:23
−
|The testdir directory is successfully deleted. Note that, testdir directory was also empty.
+
|The '''testdir''' directory is successfully deleted. Note that, '''testdir''' directory was also empty.
 
|-
 
|-
−
| 13:38
+
| 14:32
−
|Multiple directories or a hierarchy of directories can be removed at once.So, try to delete the testtree directory along with its subdirectory test3.  
+
|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
+
| 14:43
−
|Type at the command prompt
+
|Type at the command prompt '"rmdir space testtree space testtree slash test3'" press enter.
−
"rmdir space testtree space testtree slash test3 "press enter.
+
 
|-
 
|-
−
| 14:02
+
| 14:57
−
|See, it is giving the error message that 'testree' directory cannot be removed because testtree is not empty.  
+
|See, it is giving the error message that '''testree''' directory cannot be removed because testtree is not empty.  
 
|-
 
|-
−
| 14:11
+
| 15:07
−
|But one thing which you may miss is that testtree/test3 has been deleted as it was empty.  
+
|But one thing which you may miss is that '''testtree slash test3''' has been deleted as it was empty.  
 
|-
 
|-
−
| 14:19
+
| 15:16
−
|To check that, type at the command prompt "cd space testtree" and press enter.
+
|To check that, type at the command prompt "'cd space testtree"' and press enter.
 
|-
 
|-
−
| 14:27
+
| 15:25
−
|Now type "ls" and press enter. See, the directory contains nothing. So, test3 was deleted.
+
|Now type "'ls'" and press enter. See, the directory contains nothing. So, '''test3''' was deleted.
 
|-
 
|-
−
| 14:36
+
| 15:34
 
|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.  
 
|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
+
| 15:48
 
|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.
 
|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
+
| 16:02
 
|More information this is available at the following link  
 
|More information this is available at the following link  
 
|-
 
|-
−
| 15:08
+
| 16:08
−
|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.
+
|This is Anusha Kadambala signing off. Thanks for joining.
  
 
|}
 
|}

Revision as of 12:50, 4 December 2014

Time Narration
00:00 Welcome to this spoken tutorial on Linux File System.
00:04 I am using Linux Operating system.
00:08 We assume that you know how to get started with the Linux operating system and have some basic idea about commands.
00:16 If you are interested, it is available through another spoken tutorial, on the following website http://spoken-tutorial.org
00:28 Also note that linux is case sensitive.
00:32 All the commands used in this tutorial are in lower case unless otherwise mentioned.
00:41 In Linux almost everything is a file.
00:44 So what is a file? In real life we know that a file is where we store our documents and papers.
00:54 Similarly in Linux a file is a container for storing information.
01:00 Next what is a directory?
01:03 A directory can be understood as a collection of files and other (sub)directories.
01:10 A directory helps us in organising our files in a systematic manner.
01:16 This is like what we call folders in Windows.
01:20 It allows different users to have their own directories with their files which others cannot access or modify.
01:30 Also if there are no directories, all the files on the system need to have unique names,which would be very difficult to maintain.
01:41 These definitions of files and directories are good to get a general feel about them, they are not entirely accurate.
01:51 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.
02:05 Thus 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.
02:20 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 larger numbers.
02:35 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.
02:49 In fact in Linux there are three kinds of files:
02:54 Regular Files or Ordinary files: It contains only data , as a stream of characters.
03:01 Directories: As we just saw in the previous slides.
03:07 Device Files: All hardware devices and peripherals are represented as files in Linux.
03:14 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.
03:32 All files in Linux are related, in short all form a family much like we do.
03:39 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.
03:52 At the top is the root( denoted by a frontslash /). It contains all the other files and directories.
04:04 This also helps in easy navigation from one file or directory to other, if we know the correct path.
04:12 As we work with a Linux file system, it seems that we are moving along this tree.
04:18 One command and there you are teleported from one place to other.
04:24 Sounds interesting!! Indeed it is. As we will see.
04:29 When we login into the Linux system we are by default in a home directory.
04:36 Now Switch to the terminal.
04:39 To see the home directory , Type at the command prompt "'echo space dollar H-O-M-E in capital"' and press enter.
04:53 This gives the pathname of our home directory.
04:57 We can move around from one directory to other.
05:01 But any time we can be in one directory and this directory is known as the current directory or working directory.
05:09 The pwd command helps us to see the current directory. pwd stands for present working directory.
05:18 Type at the command prompt '"pwd'" and press enter. Now this is our present working directory.
05:28 We have said that we can move from one directory to other.
05:32 But how do we do so? We have the cd command for this purpose.
05:39 You have to type the command cd followed by the pathname of the directory you want to move to.
05:47 Lets again see our current directory by typing pwd at the command prompt and press enter.
05:57 So, now we are placed in this directory.
06:01 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.
06:17 Now lets see our current directory. Type pwd and press enter.
06:24 Yes we have moved to slash usr directory.
06:30 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.
06:42 Instead we may use Relative pathnames that begin from the current directory.
06:48 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.
07:02 Now let us have a brief session on cd command
07:06 The command cd without any argument is used to move back that to the home directory.
07:13 Type at the command prompt "'cd'" and press enter.
07:19 Now check our current directory by the pwd command.
07:23 So, now we are back in our home directory /home/gnuhata [ slash home slash gnuhata ]
07:30 Now let us move to music directory. Type at the command prompt "'cd space Music(M in capital) slash"' and press enter
07:43 Now check our current directory by the pwd command. pwd and press enter. See, we have moved /home/gnuhata/Music
07:57 Let us go to the parent directory of Music. For that you have to use cd command with dot dot.
08:04 Type at the command prompt cd space dot dot and press enter.
08:11 Now check our present directory by typing pwd. We are again in /home/gnuhata
08:23 Now lets try to move to a subdirectory of the current directory using dot.
08:30 Type at the command prompt cd space dot slash Documents(D in capital) slash. Press enter.
08:42 Check our current directory by typing pwd. We are at /home/gnuhata/Documents
08:53 Let me clear the screen by pressing control L. So you can see clearly.
08:58 To go back to our home directory by cd command. Type cd and press enter.
09:07 Again check our current directory by pwd command. We are back to /home/gnuhata .
09:17 We can combine any number of dot dot separated by slash in a relative path .
09:23 In this slide, we can see the file system hierarchy. Root or slash 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.
09:43 So, now we are in /home/gnuhata. Now how can we go to the bin directory?
09:51 Type at the command prompt "'cd space dot dot slash dot dot slash bin'" and press enter.
10:03 Check our current directory by the command pwd. We are at /bin (slash bin)
10:11 The first .. (dot dot) takes us from /home/gnuhata (slash home slash gnuhata) to /home (slash home)
10:18 The next takes us from slash home to root.
10:24 Now from root or slash, we have moved to /bin directory.
10:30 Go back to our home directory by the command cd.
10:34 To create a directory we use the mkdir command.
10:40 You have to type the command and name of directory to be created and a directory would be created under the current directory.
10:49 To create a directory named testdir, type the command '"mkdir space testdir'" and press enter.
11:01 This creates the testdir directory successfully.
11:05 Note that, there is no explicit notification of successful directory creation or removal.
11:13 If you do not get any error message, it denotes successful execution.
11:18 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.
11:33 This process can be used for making multiple directories or even a hierarchy of directories.
11:39 Type "'mkdir space test1 space test2 and press enter ,this will make two directories named test1 and test2 under the present directory.
11:57 Type "'mkdir space testtree space testtree slash test3'".
12:11 This will make a directory testtree and another directory test3 which is a sub-directory under testtree.
12:20 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.
12:40 Similar to the mkdir is the rmdir command which is used for removing a directory or directories.
12:50 The command "'rmdir space test1'" removes the test1 directory successfully.
13:00 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.
13:13 Now type at the command prompt '"cd space testtree slash test3"'
13:25 So, we are now in test3 directory which is a subdirectory under testtree.
13:33 Lets try to remove the testdir directory by typing the command '"rmdir space testdir'". Press enter.
13:46 We see it can't be done, because the current directory is not hierarchically above the directory to be removed.
13:54 So,we have to go to the directory which is hierarchically above testdir directory.
14:00 Type "'cd space dot dot"' and press enter.
14:06 Now, go back to our parent directory by typing the command "'cd space dot dot'".
14:13 Now, again try the previous command.
14:16 Type "rmdir space testdir". Press enter.
14:23 The testdir directory is successfully deleted. Note that, testdir directory was also empty.
14:32 Multiple directories or a hierarchy of directories can be removed at once.So, try to delete the testtree directory along with its subdirectory test3.
14:43 Type at the command prompt '"rmdir space testtree space testtree slash test3'" press enter.
14:57 See, it is giving the error message that testree directory cannot be removed because testtree is not empty.
15:07 But one thing which you may miss is that testtree slash test3 has been deleted as it was empty.
15:16 To check that, type at the command prompt "'cd space testtree"' and press enter.
15:25 Now type "'ls'" and press enter. See, the directory contains nothing. So, test3 was deleted.
15:34 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.
15:48 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.
16:02 More information this is available at the following link
16:08 This is Anusha Kadambala signing off. Thanks for joining.

Contributors and Content Editors

PoojaMoolya, Sandhya.np14

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