Linux-for-Sys-Ads/C2/Assigning-groups-on-user-creation/English - Revision history

Nancyvarkey at 11:22, 31 August 2018

2018-08-31T11:22:41Z

Nancyvarkey at 11:21, 31 August 2018

2018-08-31T11:21:52Z

Pravin1389: Created page with "'''Title of script: Assigning Groups on User Creation''' '''Author: Antara Roy Choudhury''' '''Keywords: group, primary group, supplementary group, assigning group, specify..."

2018-08-31T09:14:10Z

Created page with "'''Title of script: Assigning Groups on User Creation''' '''Author: Antara Roy Choudhury''' '''Keywords: group, primary group, supplementary group, assigning group, specify..."

New page

'''Title of script: Assigning Groups on User Creation'''

'''Author: Antara Roy Choudhury'''

'''Keywords: group, primary group, supplementary group, assigning group, specify GID, /etc/group file'''

{| border=1
|-
|| '''Visual Cue'''
|| '''Narration'''
|-
|| Slide 1: Introduction
|| Hello and welcome to the spoken tutorial on '''Assigning Groups '''on''' User Creation '''in''' Linux.'''
|-
|| Slide 2: Learning Objectives
|| In this tutorial we will learn about

*Creating a''' user group'''
*'''/etc/group file'''
*Assigning''' groups '''to '''users '''at the time of''' account creation'''

We will do this through some examples.
|-
|| Slide 3: System requirement
|| To record this tutorial, I am using '''Ubuntu Linux 16.04 OS'''
|-
|| Slide:4 Prerequisite
|| To practice this tutorial,

*you should have gone through '''Linux System Administration '''tutorials''' '''on this website.
*you must have '''root access''' to your computer.

|-
|| Slide 5:
|| What is a '''group '''in''' Linux'''?

*We can understand '''group''' as a '''collection of users'''.
*In a college system, a '''group '''can be '''different departments''' like '''CSE''', '''Electrical''' etc.
*Groups can also be different clubs like '''music club''',''' sports club, literature club,''' etc.

|-
|| Slide 6:
|| '''Linux''' supports two types of '''groups'''.

*'''Primary group '''and''' '''
* '''Supplementary group '''

|-
|| Slide 7:
|| *Every '''user''' must belong to one and only one''' primary group'''.
*This is the default''' group''' for the '''user''' when the '''user '''logs in.
*For example: a student must belong to one and only one '''department'''.

|-
|| Slide 8:
|| *A '''user''' can be a member of more than one '''group'''.
*Those '''groups '''are called '''supplementary groups'''.
*These '''groups '''are assigned to the '''user''', to provide him additional '''access''' to resources.

More on '''access''' mechanism or '''permission''' will be discussed in subsequent tutorials.
|-
|| Slide 9
|| Let’s take an example.*'''User radha '''belongs to the '''CSE department'''.
*She is also a member of the '''music club '''and '''sports club'''.
*In this scenario, '''CSE''' is the '''primary group '''for '''radha'''.
*And she is a member of two '''supplementary groups '''- '''music club '''and '''sports club'''.

Let’s create this scenario in our system.
|-
||
|| First, we will create '''group CSE'''.

And we will use '''addgroup command '''in order to create this '''group'''.
|-
|| Press Ctrl+Alt+T
|| Open the '''Terminal '''by pressing '''Ctrl, Alt and T '''keys simultaneously on the keyboard.
|-
|| Type

sudo su

[Enter]
|| Now, we should login as '''superuser '''or '''root user'''.

To do so type: '''sudo space su '''and press '''Enter.'''
|-
|| Type

Password of your account

[Enter]
|| Type the admin '''password '''and then press '''Enter'''.
|-
|| Highlight # prompt
|| Notice, our '''login prompt '''has changed to''' '''a '''hash''' symbol.

This indicates that we are in the '''root user '''mode.
|-
|| Only narration
|| Here onwards, please remember to press the '''Enter''' key after typing each '''command'''.
|-
|| Type

addgroup cse [Enter]
|| Now type '''addgroup space cse'''
|-
|| Show the output

{Suppose output is

Adding group cse (GID 1009)}
|| This will create '''group cse'''.

'''Linux''' automatically allocates a '''Unique ID''' for each '''group''' that is created.

Here, '''GID, '''that is '''Group ID''' is '''1002'''.
|-
|| Slide 10
|| *Alternatively, we can mention a '''GID '''of our choice.
*For this, we need to use '''hyphen gid''' option along with the '''addgroup command'''.
*'''GIDs''' in the range of''' 0 '''to''' 999''' are '''reserved''' for the '''system users'''.
*So, always choose a number greater than or equal to '''1000''' as '''GID'''

|-
||
|| Let’s us create a '''group Music_club''' with the''' GID 1012.'''
|-
|| Type:

addgroup -gid 1012 Music_club

[Enter]
|| On the '''terminal '''type:

'''addgroup space hyphen gid 1012 space Music underscore club '''

Here type '''M''' is in '''capital letter.'''
|-
|| Show the output
|| Notice, it is showing some error.

Actually, we should have written '''m '''in '''lowercase '''letter'''.'''

Let’s try that.
|-
|| Press Up key
|| Press the '''Up''' arrow key to get the previously executed command.
|-
|| Change Music_club to music_club [Enter]
|| Change '''capital M''' to '''m''' in '''lowercase''' letter.
|-
|| Show the output
|| The '''command''' is working now.

So, always remember to use '''lowercase '''letters while writing '''group '''names.
|-
|| Type

addgroup sports_club

[Enter]
|| Similarly let’s create another '''group sports underscore club'''.

This time no need to mention the '''GID'''.
|-
||
|| Now we have three groups '''cse, music underscore club '''and''' sports underscore club'''.
|-
|| cat /etc/group

[Enter]
|| How can we check the details of the created '''group'''?

Type '''cat space /etc/group'''
|-
|| Show file opened
|| There will be an entry in this file for every '''user''' on the '''system.'''
|-
|| slide

Highlight on the slide

|| Each line has four '''fields''' separated by a '''colon '''symbol.

The first '''field''' is the name of the '''group.'''

The second '''field''' is the '''encrypted password''' for the '''group'''.

Third '''field''' shows the '''GID '''as a number.
|-
||

Highlight on the slide
|| Fourth '''field''' contains the list of '''users''' that belong to that '''group '''separated by '''commas'''.

This list contains all '''users''' who have this '''group''' as a '''secondary group.'''
|-
|| Show file /etc/group

Highlight groups cse, music_club, sports_club
|| We can see the entries for '''cse, music underscore club''' and '''sports underscore club groups.'''

Notice, '''music underscore club''' has '''Gid 1012 '''which we mentioned during '''group '''creation.

Here, the fourth '''field '''is empty for all the '''groups'''.

This is because there are no members in these '''groups''', as of now.

The '''password field '''is '''x'''.

We will discuss about the '''password field '''and list of members '''field '''in detail, in a separate tutorial on '''groups'''.
|-
|| Retain same screen
|| Now, how can we specify the '''primary '''and''' supplementary groups''' while creating the '''user'''?

Let us see an example.
|-
|| Type

adduser -ingroup cse radha

[Enter]
|| To specify that '''user radha '''belongs to the '''primary group cse''', type:

'''adduser space hyphen ingroup space cse space radha '''
|-
|| Type

pass_radha

[enter]
|| Type the '''password '''as '''pass underscore radha''' and press '''Enter.'''

Retype the same password and press '''Enter.'''

Type name as '''Radha''' with '''capital R'''.

And proceed as we have done before.
|-
|| Show output
|| We have successfully created '''user radha''' with '''primary group cse'''.
|-
|| Highlight ingroup
|| So, you should use '''ingroup option''' to specify''' primary group'''’s name while creating the '''user'''.
|-
|| adduser radha music_club

[Enter]
|| As we know, '''radha''' is a member of '''music underscore club'''.

So '''music underscore club''' will be the '''supplementary group''' for the '''user radha.'''

Type '''adduser space radha space music underscore club'''
|-
|| Retain same screen
|| Remember.

To add '''supplementary groups''' using '''adduser command''', you should have an existing '''user'''.
|-
|| Highlight

adduser -ingroup cse radha

command executed previously
|| Here, we have first created the '''user radha.'''
|-
|| Highlight

adduser radha music_club
|| Then added '''radha''' to the '''supplementary group''' using '''adduser command.'''
|-
|| adduser radha sports_club
|| If you need to specify that '''radha''' is also a member of '''sports club '''type:

'''adduser space radha space sports underscore club'''
|-
|| id radha
|| Let’s check '''user radha'''’s details using '''id command'''.

Type '''id space radha'''
|-
|| Show the output

|| Notice,

User '''radha''' is in group '''cse''' which has '''GID''' 1002

That is the''' primary group''' for '''radha'''.

Next, there is the list of '''groups''',where '''user radha '''is member of.

Notice, along with '''primary group cse, radha''' is also a member of two '''supplementary groups music underscore club''' and '''sports underscore club.'''
|-
|| Type

grep radha /etc/group

[Enter]
|| Now let’s check our '''/etc/group file''' for the entry of '''radha'''

Type: '''grep space radha space /etc/group'''
|-
|| Highlight appropriately in the output
|| Notice, you can see '''user radha''' is the member of '''groups music underscore club''' and '''sports underscore club'''

But not as a member of the '''primary group''' that is '''cse'''.

So the '''group file''' will list only the''' supplementary groups''' in which the '''user''' is associated.
|-
|| Type

grep radha /etc/passwd

[Enter]
|| Check the '''/etc/passwd file''' for the details of the '''username radha.'''

Type '''grep space radha space /etc/passwd'''
|-
|| Show the output
|| Notice, the fourth '''field''' is '''1002'''

It is the '''GID''' for the '''group cse'''.

It is the '''primary group''' for '''radha.'''
|-
|| Slide 13:
|| So, remember*'''/etc/passwd''' shows '''primary group ID '''for a '''user'''
*'''/etc/group file''' shows list of '''usernames''' who have the''' group '''as a '''supplementary group'''

|-
|| Slide 14:
|| Command '''id space username''' shows the details of both''' primary '''and''' supplementary groups'''
|-
|| Retain same screen
|| You can also specify the '''group id''' instead of''' group'''’s name while creating the '''user'''.

Let us create a '''user suraj''' and assign him to the '''group cse''' using the '''gid'''.

We know''' group cse''' has '''GID 1002'''
|-
|| Type

adduser -gid 1009 suraj

[Enter]
|| So type: '''adduser space hyphen gid space 1002 space suraj'''

You should use '''hyphen gid option''' to specify the '''group ID'''.

Use '''pass underscore suraj''' as the '''password'''

Retype the '''password'''

Full Name as '''Suraj''' with '''S''' in capital letter.

Proceed as we have done for the previous '''users'''.
|-
|| Highlight the output
|| We have successfully created '''user suraj '''with '''primary group cse.'''
|-
|| Type

exit and press '''Enter'''
|| To exit from the '''root user access''', type '''exit'''
|-
|| Retain same screen
|| This brings us to the end of this tutorial.

Let us summarize.
|-
|| Display Slide 15

Summary
|| In this tutorial we learnt about-

*Creating''' primary group'''
*Assigning '''user '''to the '''primary group'''
*Assigning''' user '''to the '''supplementary group'''
*'''/etc/group file'''
*Assigning''' groups '''to''' users '''at the time of''' account creation'''

|-
|| Display Slide 16

Assignment

|| As an assignment-

#Create two '''groups: '''
##'''cultural '''
##'''literature'''

|-
|| Slide 17

Assignment(Cont.)
|| #Now create a''' user ajay''' with
##'''Home directory''' as '''/home/ajay underscore dir '''
##'''User id '''as''' 1090'''
##'''Primary group '''as '''cultural'''
##'''Supplementary group '''as '''literature'''
##Add '''comments "Native: Mumbai"'''

|-
|| Slide 18

Assignment(Cont.)
|| 3) Use the '''command id''' to check the '''user '''details

4) Check the details of '''user ajay '''in '''/etc/passwd '''and '''/etc/group files'''
|- style="border:1pt solid #000001;padding-top:0.106cm;padding-bottom:0.106cm;padding-left:0.071cm;padding-right:0.106cm;"
|| Slide 19: About Spoken Tutorial project
|| The video at the following link summarises the Spoken Tutorial project.

Please download and watch it.
|- style="border:1pt solid #000001;padding-top:0.106cm;padding-bottom:0.106cm;padding-left:0.071cm;padding-right:0.106cm;"
|| Slide 20: Spoken Tutorial workshops
|| The Spoken Tutorial Project team conducts workshops and gives certificates.

For more details, please write to us.
|-
|| Slide 21: Forum for specific questions:
|| Please post your timed queries in this forum.
|- style="border:1pt solid #000001;padding-top:0.106cm;padding-bottom:0.106cm;padding-left:0.071cm;padding-right:0.106cm;"
|| Slide 22: Acknowledgement
|| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at this link.
|-
|| Slide 23: Thank You
|| The script has been contributed by Antara and this is Praveen from IIT Bombay signing off.

Thank you for joining.
|-
|}

@@ Line 39: / Line 39: @@
 *We can understand '''group''' as a '''collection of users'''.
 *In a college system, a '''group '''can be '''different departments''' like '''CSE''', '''Electrical''' etc.
-*Groups can also be different clubs like '''music club''',''' sports club, literature club,''' etc.
+*'''Groups''' can also be different clubs like '''music club''',''' sports club, literature club,''' etc.
 |-

@@ Line 50: / Line 50: @@
 |-
 || Slide 7:
-|| *Every '''user''' must belong to one and only one''' primary group'''.
+||
 *This is the default''' group''' for the '''user''' when the '''user '''logs in.
 *For example: a student must belong to one and only one '''department'''.
@@ Line 56: / Line 57: @@
 |-
 || Slide 8:
-|| *A '''user''' can be a member of more than one '''group'''.
+||
 *Those '''groups '''are called '''supplementary groups'''.
 *These '''groups '''are assigned to the '''user''', to provide him additional '''access''' to resources.
@@ Line 63: / Line 65: @@
 |-
 || Slide 9
-|| Let’s take an example.*'''User radha '''belongs to the '''CSE department'''.
+|| Let’s take an example.
 *She is also a member of the '''music club '''and '''sports club'''.
 *In this scenario, '''CSE''' is the '''primary group '''for '''radha'''.
@@ Line 119: / Line 122: @@
 |-
 || Slide 10
-|| *Alternatively, we can mention a '''GID '''of our choice.
+||
 *For this, we need to use '''hyphen gid''' option along with the '''addgroup command'''.
 *'''GIDs''' in the range of''' 0 '''to''' 999''' are '''reserved''' for the '''system users'''.
@@ Line 288: / Line 292: @@
 || Notice,
-User '''radha''' is in group '''cse''' which has '''GID''' 1002
+'''User radha''' is in group '''cse''' which has '''GID''' 1002
 That is the''' primary group''' for '''radha'''.
-Next, there is the list of '''groups''',where '''user radha '''is member of.
+Next, there is the list of '''groups''', where '''user radha '''is member of.
 Notice, along with '''primary group cse, radha''' is also a member of two '''supplementary groups music underscore club''' and '''sports underscore club.'''
@@ Line 329: / Line 333: @@
 |-
 || Slide 13:
-|| So, remember*'''/etc/passwd''' shows '''primary group ID '''for a '''user'''
+|| So, remember
 *'''/etc/group file''' shows list of '''usernames''' who have the''' group '''as a '''supplementary group'''
@@ Line 391: / Line 396: @@
 || As an assignment-
-#Create two '''groups: '''
+)Create two '''groups: '''
-##'''cultural '''
+#'''cultural '''
-##'''literature'''
+#'''literature'''
 |-
@@ Line 399: / Line 404: @@
 Assignment(Cont.)
-|| #Now create a''' user ajay''' with
+||
-##'''Home directory''' as '''/home/ajay underscore dir '''
+)Now create a''' user ajay''' with
-##'''User id '''as''' 1090'''
+#'''Home directory''' as '''/home/ajay underscore dir '''
-##'''Primary group '''as '''cultural'''
+#'''User id '''as''' 1090'''
-##'''Supplementary group '''as '''literature'''
+#'''Primary group '''as '''cultural'''
-##Add '''comments "Native: Mumbai"'''
+#'''Supplementary group '''as '''literature'''
 |-