PoojaMoolya: Created page with " {| border=1 |- || '''Time''' || '''Narration''' |- || 00:01 || Hello and welcome to the spoken tutorial on '''Modifying and Deleting Groups in Linux.''' |- || 00:09 || In th..."

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|-
|| '''Time'''
|| '''Narration'''
|-
|| 00:01
|| Hello and welcome to the spoken tutorial on '''Modifying and Deleting Groups in Linux.'''

|-
|| 00:09
|| In this tutorial we will learn about

'''groupmod command '''and '''groupdel command '''

|-
|| 00:17
|| We will do this through some examples.
|-
|| 00:21
|| To record this tutorial, I am using '''Ubuntu Linux 16.04 OS'''
|-
|| 00:28
|| To practice this tutorial, you should have gone through the '''Linux System Administration '''tutorials''' '''on this website and

|-
|| 00:36
|| you must have '''root access''' to your computer.

|-
|| 00:41
|| Open the '''Terminal '''by pressing '''Ctrl, Alt and T '''keys simultaneously on the keyboard.
|-
|| 00:49
|| First, you should login as '''superuser '''or '''root user'''.
|-
|| 00:56
|| Here onwards, please remember to press the '''Enter''' key after typing each '''command'''.
|-
|| 01:03
|| In the series, we had created the '''group electronics.'''

|-
|| 01:07
|| Let us check the details of the '''group '''from the '''/etc/group''' file.
|-
|| 01:14
|| Notice that '''group electronics''' has '''GID''' 1006.
|-
|| 01:20
|| Also, the list of members field is empty.

|-
|| 01:25
|| So, no '''user''' has '''group electronics''' as a '''supplementary group'''.
|-
|| 01:31
|| Let’s check the '''/etc/passwd''' file to know how many '''users''' belong to the '''primary group electronics.'''
|-
|| 01:42
|| Notice that, the '''users testmod''' and '''amit''' have '''1006''' in the fourth '''field'''.

|-
|| 01:50
|| It means the users''' testmod '''and''' amit '''belong to the '''group electronics'''
|-
|| 01:57
|| Let me create a document '''testfile.txt '''in the user account''' testmod'''
|-
|| 02:04
|| '''So, login''' as '''user testmod'''
|-
|| 02:08
|| Now if we create any document, then that document will be owned by the '''group electronics.'''Let's do that.
|-
|| 02:17
|| First we’ll create a text file named '''testfile.txt'''

|-
|| 02:24
|| I am going to use '''vi text editor '''to do so.

|-
|| 02:28
|| But you can use any other '''text editor '''of your choice.

|-
|| 02:33
|| At the '''command prompt''' type '''vi space testfile.txt '''
|-
|| 02:41
|| Press '''I''' on the keyboard to insert text.
|-
|| 02:45
|| Now type this text, “'''Hi I am user testmod'''”
|-
|| 02:50
|| Press the '''Escape''' key on the keyboard to exit from the '''insert mode'''.
|-
|| 02:55
|| Then press '''colon w q'''

|-
|| 02:59
|| '''w''' is used to save the typed text in the text file.

|-
|| 03:04
|| And '''q''' is used to quit the '''editor'''.

Now press '''Enter.'''
|-
|| 03:11
|| We are back to the '''command prompt'''.
|-
|| 03:14
|| Now type, '''ls space hyphen l space testfile.txt'''
|-
|| 03:22
|| Notice the third and fourth '''fields'''.

|-
|| 03:25
|| The document belongs to '''user testmod''' and '''group electronics.'''
|-
|| 03:31
|| Now let us start modifying the '''group''' with the '''groupmod command.'''
|-
|| 03:37
|| The '''groupmod command''' is used to modify the definition of the '''group '''specified in the''' command'''.

|-
|| 03:45
|| This is the syntax.

|-
|| 03:49
|| Here the '''options field''' is not mandatory.
|-
|| 03:54
|| '''groupmod command''' can be used to modify- the '''group '''name,

'''GID'''

|-
|| 04:00
|| '''GID''' to a non-unique number

|-
|| 04:04
|| Suppose, we want to modify our '''group'''’s name from '''electronics''' to '''electrical'''.

|-
|| 04:10
|| To do so, let me switch back to the '''root login'''.

|-
|| 04:15
|| Exit from the '''user testmod'''.
|-
|| 04:19
|| Now type '''groupmod space hyphen n space electrical space electronics'''
|-
|| 04:28
|| Then type '''cat space /etc/group'''
|-
|| 04:34
|| Notice that the '''group''' with '''GID 1006''' is now named as '''electrical.'''
|-
|| 04:42
|| You can also change the '''GID''' of a '''group''' to a new unique non-negative number.

|-
|| 04:50
|| Suppose, you are planning to use number '''1100''' as the new '''GID''' value.

|-
|| 04:57
|| So, first ensure, that the number '''1100''' is not present as '''GID''' in any other '''group'''.

|-
|| 05:06
|| From the output of '''/etc/group 1100''' is not set as a '''GID''' value to any of the '''group'''.

|-
|| 05:16
|| This type of manual checking is not a good idea, if you have a large number of '''groups'''.

|-
|| 05:22
|| Instead we can use the '''grep command''' to check if the number is present or not.

|-
|| 05:30
|| As an assignment, try this out on your own.
|-
|| 05:35
|| Now to change '''GID''' value, type '''groupmod space hyphen g space 1100 space electrical'''
|-
|| 05:48
|| Now check the details of the file''' /etc/group'''
|-
|| 05:54
|| Notice that '''GID''' of '''electrical''' is now '''1100.'''
|-
|| 06:00
|| We know that '''user testmod''' belongs to the '''group electrical.'''

|-
|| 06:05
|| Let’s check '''/etc/passwd '''file for the entry of the '''user testmod'''.
|-
|| 06:14
|| Notice that the '''GID''' value in the fourth '''field''' is also updated.

|-
|| 06:19
|| It is showing the current value '''1100.'''
|-
|| 06:24
|| The '''group ID''' has changed.

|-
|| 06:27
|| But the files belonging to this '''group''' will retain the old '''group ID''' value.

|-
|| 06:34
|| So we must change their '''group ID''' manually.
|-
|| 06:39
|| To find all files belonging to the '''group''' with '''GID 1100''', type '''find space slash home space hyphen gid space 1100'''
|-
|| 06:55
|| This may take some time.

|-
|| 06:58
|| We have not got any output.

|-
|| 07:01
|| Recall the previous '''command'''.

|-
|| 07:04
|| Change the '''group ID''' value to '''1006''' that is the previous '''group ID''' of '''electrical'''.
|-
|| 07:12
|| Notice, the file '''testfile.txt''' still belongs to '''group ID 1006.'''

|-
|| 07:20
|| Please note the complete '''path''' of the file '''testfile.txt'''
|-
|| 07:26
|| To change the '''group ID''' for the file '''testfile.txt''' to '''1100''', type

'''chgrp space 1100 space ''', then type the full''' path '''of file''' testfile.txt.'''

|-
|| 07:44
|| '''chgrp command''' is used to change the '''group''' of the file.
|-
|| 07:49
|| The '''command''' has executed without any error.
|-
|| 07:53
|| Recall the '''command''' to display all the files belonging to''' group ID 1100.'''
|-
|| 08:00
|| Notice the output shows '''testfile.txt '''file.

|-
|| 08:05
|| Please note, you may have multiple files belonging to old '''group ID''' value.

|-
|| 08:12
|| Changing '''group ID''' manually one by one will be a tedious job in that case.

|-
|| 08:18
|| Try writing '''shell script '''for this.
|-
|| 08:22
|| Now we know how to change the '''GID''' of a '''group''' to another unique value.

Let’s move on.
|-
|| 08:30
|| Recall the '''command''' to display '''/etc/group'''.
|-
|| 08:36
|| Notice, '''literature club''' has '''GID 1007'''.

|-
|| 08:42
|| Let us try to assign this '''1007''' as the new '''GID''' of '''electrical.'''
|-
|| 08:49
|| Notice, it is showing an error, '''GID 1007 already exists.'''

|-
|| 08:56
|| So, we cannot change the '''group ID '''to a non-unique value with only '''hyphen g''' option.
|-
|| 09:04
|| To change the '''group ID''' to a non-unique value, you will need '''hyphen o option''' along with '''hyphen g option'''

|-
|| 09:14
|| Let me try to set the '''GID''' to '''1007''' now.

|-
|| 09:19
|| Recall the previous '''command.'''
|-
|| 09:22
|| Now, after '''1007''', give '''space''' and then type '''hyphen o'''
|-
|| 09:30
|| The '''command''' has executed successfully.
|-
|| 09:34
|| Next, execute the '''cat /etc/group command'''
|-
|| 09:41
|| Notice that both '''electrical''' and '''literature_club''' now have same '''GID 1007.'''
|-
|| 09:50
|| So, we have learnt about '''groupmod command'''.

|-
|| 09:54
|| Now let’s learn about '''groupdel command.'''
|-
|| 09:58
|| '''groupdel command''' is used by the '''root''' or the '''superuser''' to remove a '''group'''.

|-
|| 10:05
|| Syntax is '''groupdel space groupname'''
|-
|| 10:10
|| Let me remove the '''group''' named '''electrical'''.

|-
|| 10:14
|| Type '''groupdel space electrical'''
|-
|| 10:19
|| Notice that '''Linux''' has thrown some error.

|-
|| 10:23
|| It is telling that '''cannot remove primary group of the user amit'''

|-
|| 10:29
|| So, you cannot delete '''electrical''' because it is the '''primary group''' of an existing '''user amit.'''

|-
|| 10:37
|| You must first delete the '''user amit''' and then you can remove '''electrical'''.

Let’s try this.
|-
|| 10:46
|| For deleting user '''amit''', type '''userdel space hyphen r space amit'''
|-
|| 10:54
|| The '''command''' may report that the '''user's mail spool''' was not found.

This warning can be ignored.
|-
|| 11:03
|| Now execute the '''groupdel command.'''
|-
|| 11:07
|| Once again we got the error.

Says, '''cannot remove the primary group of the user testmod'''
|-
|| 11:15
|| Let me delete the user '''testmod'''.
|-
|| 11:19
|| Once again we got the '''user's mail spool''' error.
|-
|| 11:24
|| Now execute the '''groupdel command '''for the '''group electrical'''.
|-
|| 11:29
|| This time we did not get any error.

|-
|| 11:33
|| Now execute the '''cat /etc/group command'''
|-
|| 11:40
|| We can see that there is no entry for '''electrical'''.

|-
|| 11:44
|| The '''group''' named '''electrical''' is deleted now.
|-
|| 11:48
|| The important point you have to keep in mind is:

You are not permitted to remove the '''primary group''' of any existing '''user'''.

|-
|| 11:58
|| You must remove the '''user''' first. Then you can remove that '''user's primary group'''.

|-
|| 12:05
|| Now what about the files owned by the deleted '''group'''?

|-
|| 12:09
|| '''groupdel''' will not automatically check for files owned by the deleted '''group'''.

|-
|| 12:15
|| You should manually search all '''file systems''' for such files.

|-
|| 12:21
|| You can use the '''find command''' for this search.

|-
|| 12:25
|| You should ensure that no files remain owned by this deleted '''group'''.

|-
|| 12:31
|| You can either delete those files or change the '''group ownership''' using '''chgrp command.'''

I leave it as an exercise for you.
|-
|| 12:43
|| Switch to the '''terminal'''.

|-
|| 12:45
|| Exit from the '''root user access'''.
|-
|| 12:49
|| This brings us to the end of this tutorial.

Let us summarize.
|-
|| 12:55
|| In this tutorial we learnt about-

'''groupmod command '''to modify the '''group '''name
|-
|| 13:02
|| '''GID'''

'''GID '''to a non-unique number
|-
|| 13:08
|| '''groupdel command''' to delete a '''group'''

|-
|| 13:11
|| As an assignment: Create two new '''groups'''

'''civil''' with '''GID 1201''', '''mechanical''' with '''GID 1202'''

|-
|| 13:24
|| Add a '''user suman''' with '''primary group civil'''

|-
|| 13:29
|| Let '''suman''' create a document '''test.txt''' and type any text of your choice.

|-
|| 13:36
|| Modify the '''GID''' of the '''group civil''' to '''1203'''

|-
|| 13:42
|| Change the '''group ownership''' of the file '''test.txt'''.

|-
|| 13:47
|| Delete '''group civil '''

|-
|| 13:49
|| Delete file '''test.txt'''

|-
|| 13:53
|| The video at the following link summarises the Spoken Tutorial project.

Please download and watch it.
|-
|| 14:01
|| The Spoken Tutorial Project team conducts workshops using spoken tutorials and gives certificates.

For more details, please write to us.
|-
|| 14:13
|| Pls post your timed queries in this Forum.
|-
|| 14:17
|| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

|-
|| 14:23
|| The script has been contributed by Antara. And this is Praveen from IIT Bombay signing off.

Thanks for joining.
|-
|}

Linux-for-Sys-Ads/C2/Modifying-and-Deleting-Groups/English-timed - Revision history

PoojaMoolya: Created page with " {| border=1 |- || '''Time''' || '''Narration''' |- || 00:01 || Hello and welcome to the spoken tutorial on '''Modifying and Deleting Groups in Linux.''' |- || 00:09 || In th..."