View source for Linux-for-Sys-Ads/C2/Group-Password-and-Login/English

'''Title of script:''' '''Group Password and Login'''

'''Author:''' Antara Roy Choudhury

'''Keywords:''' Group password, login to a group, gpasswd, newgrp, su


{| border=1
|-
|| '''Visual Cue'''
|| '''Narration'''
|-
|| Slide 1: Introduction
|| Hello and welcome to the spoken tutorial on '''Group Password '''and''' Login.'''
|-
|| Slide 2: Learning Objectives
|| In this tutorial we will learn about

* '''newgrp command'''
* Securing a '''group '''with''' password'''
* Login to a''' group '''as '''group member'''
* Login to a''' group '''as '''non-member'''

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 the '''Linux System Administration '''tutorials''' '''on this website and
* you must have '''root access''' to your computer.

|-
|| Slide 5:
|| Earlier in the series, we had created two '''users, suraj '''and''' testmod'''.

Let us check the status of these '''users'''.
|-
|| Press Ctrl+Alt+T
|| Open the '''Terminal '''by pressing '''Ctrl, Alt and T '''keys simultaneously on the keyboard.
|-
|| Type sudo su [Enter]

Password of your account

[Enter]
|| First, login as '''superuser '''or '''root user'''.
|-
|| Only narration
|| Here onwards, please remember to press the '''Enter''' key after typing each '''command'''.
|-
|| Type''' id suraj '''[Enter]
|| Now type '''id''' '''space''' '''suraj'''
|-
|| Show the output and highlight
|| The output indicates that '''Suraj''' belongs to '''primary group CSE.'''

He is not a member of any additional '''supplementary group'''.
|-
|| Type '''id testmod''' [Enter]
|| Now type '''id space testmod'''
|-
|| Show the output and highlight
|| The output shows that '''user testmod''' belongs to '''primary group Electronics'''.

He is also a member of two '''supplementary groups -''' '''music_club''' and '''literature_club'''
|-
|| 
|| For this demonstration, we will use the '''group music_club'''. 

We will first check the details of the '''group music_club.'''
|-
|| Type

grep "music_club" /etc/group

[Enter]
|| Type the command as shown
|-
|| Show the output and highlight
|| The output shows the details of the '''group music_club.'''

Here the value of the second '''field''' i.e. the '''password field''' is '''x'''.

So, for '''password''' details we have to refer to the '''/etc/gshadow '''file.
|-
|| change group to gshadow

Command should be:

grep "music_club" /etc/gshadow

[Enter]
|| So type the command as shown.
|-
|| Highlight the second field
|| Here, the value of the second '''field''' is an exclamation mark.

This means that the '''password''' is either invalid or not set.
|-
|| Highlight appropriately in the output
|| Also, we can see that '''testmod''' is listed as a member of the '''group music_club.'''
|-
|| Retain same screen
|| It is clear that the '''group music_club''' does not have a valid '''password'''.

Now, let us check how a member like '''testmod''' and a non-member like '''suraj''' can login to this '''group'''.

For login to a '''group''', we will use''' newgrp command.'''
|-
|| Slide 6A:
|| 
* The '''newgrp command '''is used to change the current '''group ID '''during a '''login session'''.
* The syntax of '''newgrp command '''is'''-'''

'''newgrp space hyphen space Newgroup'''
* Here, '''hyphen''' and '''Newgroup''' are optional parameters

|-
|| Slide 6B
|| 
* '''Newgroup''' is either a '''group ID '''number or a '''group''' name located in '''/etc/group'''.

|-
|| Slide 6C
|| 
* Then '''newgrp''' refers to the file''' /etc/passwd''' for the particular entry of the '''user'''.
* And changes the current '''group''' to the default '''group''' listed in the file '''/etc/passwd''' for the '''user'''.

|-
|| Slide 7:
|| 
* Optional '''hyphen flag''' re-initializes the '''user's '''environment as though the '''user '''has just logged in.
* Otherwise, the current environment remains unchanged.

For the demonstration in this tutorial, we will always use the '''hyphen flag'''.
|-
|| 
|| Let me try to login to the '''group music_club '''as a member, say '''testmod'''.

For this we have to '''login''' to '''user account testmod'''
|-
|| Click on Terminal
|| We will open a new '''terminal '''window for this.

Right click on the '''terminal.'''

From the pop-up select '''Open Terminal.'''
|-
|| Show the two terminals side by side or up & down
|| From this point onwards, we will use both these '''terminals'''.

We will switch from one '''terminal''' to another terminal for demonstration purpose.
|-
|| Highlight spoken@spoken$
|| In the new '''terminal''' we are logged in as '''user spoken.'''

Now, let me login as '''user testmod.'''
|-
|| Type '''su - testmod''' [Enter]

'''pass_radha '''[Enter]
|| Type '''su space hyphen space testmod'''
|-
|| Type '''id''' [Enter]
|| Then type '''id '''
|-
|| Highlight in the output
|| '''music_club''' is listed as one of the''' supplementary groups.'''
|-
|| Type:

newgrp - music_club

[Enter]
|| In order to '''login''' to '''group music_club''', type-

'''newgrp space hyphen space music underscore club'''
|-
|| On getting $ prompt back
|| The '''command''' has executed without any error.
|-
|| Type id [Enter]
|| Type '''id '''once again.
|-
|| Highlight in the output
|| Notice now that our current '''group''' is '''music_club'''.
|-
|| Highlight in the output of the previous command
|| Earlier it was '''Electronics'''.

So, our current''' group''' has changed.

We are logged in to '''music_club'''.

This '''login session''' will continue until we execute the '''exit command'''.
|-
|| Type exit [Enter]
|| So, let’s now type '''exit '''command
|-
|| Type id [Enter]
|| Recall the '''id''' command
|-
|| Highlight in the output
|| Now, our current group is '''Electronics'''.
|-
|| Type exit [Enter]
|| To exit from this '''user login session''', type '''exit.'''
|-
|| Highlight spoken@spoken$
|| Notice that the '''terminal prompt '''has changed.

Currently, we are logged in as '''user spoken'''.
|-
|| 
|| Now, let’s see how a non-member like '''suraj''' can '''login''' to the '''group music_club.'''

Let us try to use the same '''newgrp command''' for this purpose.
|-
|| Type su - suraj [Enter]

Type '''pass_suraj '''[Enter]
|| Let me '''login''' as '''user suraj'''
|-
|| Highlight login prompt

suraj@ubuntu$
|| We are logged in as '''suraj'''.
|-
|| Type id [Enter]
|| Type '''id'''
|-
|| Highlight in the output
|| Notice that our current '''group''' is '''CSE'''.

And there are no '''supplementary groups''' listed.

So, it's clear that '''suraj '''is not member of the''' group music_club.'''
|-
|| Type: 

newgrp - music_club [Enter]
|| Let me '''login''' to '''group music_club'''
|-
|| Show the output
|| It is asking the '''password'''.

But we haven’t set any valid '''password''' for the '''group music_club.'''

We cannot login to the '''group music_club.'''
|-
|| Press Ctrl and D

[Enter]
|| Press '''Control''' and '''D''' keys together to '''exit''' the '''group login''' process.
|-
|| Type exit [Enter]
|| Now '''exit''' from the '''user login session'''
|-
|| Highlight spoken@spoken$
|| We are back to the '''user account spoken'''.
|-
|| Slide 8:
|| From this we understand that 

* if a''' group''' does not have a valid''' password '''set, 
* then only a '''group '''member can use '''newgrp - group command''' to''' login''' to the''' group'''.
* Non-members cannot '''login''' to the''' group'''.

|-
|| Slide 9:
|| So, let us secure the '''group access '''with a '''password'''.

* '''Superuser''' or '''group administrator '''
** can use '''gpasswd space Newgroup'''
** to set or change the '''password''' of a '''group.'''
* '''Newgroup''' is either a '''group ID''' or a '''group''' name that you have to write in the '''command'''.

We will discuss about the '''group administrator''' in a separate tutorial later.

Let us now try to set the''' password''' as '''superuser'''.
|-
|| Press Alt+Tab
|| Switch to the '''terminal''' in which we have logged in as a '''root user.'''
|-
|| Type

gpasswd music_club

[Enter]
|| To set the '''password''' for the '''group music_club''', type

'''gpasswd space '''the name of the '''group '''that is '''music underscore club'''
|-
|| Type pass_music [Enter]
|| Type '''group password''' as '''pass underscore music'''

Press''' Enter'''
|-
|| Type pass_music
|| Retype the same '''password '''and press '''Enter.'''
|-
|| 
|| Now we will repeat the '''login''' process to the '''group music_club''' as a member and also as a non-member.
|-
|| Press ALT+TAB
|| Switch to the other '''terminal '''where we have logged in as user '''spoken'''
|-
|| Type su - testmod [Enter]

Type pass_radha [Enter]
|| Let me login as '''user testmod'''.
|-
|| Type:

newgrp - music_club [Enter]
|| Now '''login''' to the '''group music_club'''

The '''command''' has executed without any error.
|-
|| Type id [Enter]
|| Type '''id'''
|-
|| Highlight in the output
|| Notice that our current''' group''' is now '''music_club'''.
|-
|| Slide 10
|| So what do we understand from this?

* Even though the '''group '''has a''' password, '''
* '''group''' members will not be prompted to provide the '''password '''while logging in.

|-
|| Type exit [Enter]
|| Exit from the '''group login session''',
|-
|| Type exit [Enter]
|| Exit from the '''user testmod'''.
|-
|| Highlight spoken@spoken$
|| We are back to the user prompt '''spoken.'''
|-
|| 
|| Now, '''suraj''' is a non-member for the '''group music_club.'''

Let’s see if '''suraj''' can use the same '''newgrp command '''to '''login''' to the '''group'''.
|-
|| Type su - suraj [Enter]

Type pass_suraj [Enter]
|| '''login''' as''' user suraj'''
|-
|| Type id [Enter]
|| Type the '''id command'''
|-
|| Highlight in the output
|| As we know '''suraj''' is not a member of any '''supplementary group.'''
|-
|| Type: newgrp - music_club

[Enter]
|| Now login to''' '''the '''group music_club''', 
|-
|| Show the output
|| It is asking for a '''password'''.
|-
|| Type pass_music [Enter]
|| Type '''pass underscore music '''which we set just now.
|-
|| On getting $ prompt back
|| The command has executed without any error.
|-
|| Type id [Enter]
|| Type '''id '''command
|-
|| Highlight in the output
|| Notice, our current '''group''' is now''' music_club'''.
|-
|| Slide 11
|| So what do we understand from this?

* If the '''group''' has a '''password''' set,
* Non-members have to provide the correct '''password''' in order to login to the '''group'''.

|-
|| Type newgrp [Enter]
|| To switch back to your original '''login group''', type '''newgrp'''
|-
|| Retain same screen
|| Now, '''newgrp command''' is used without any '''argument'''.

It should change the current '''group''' to the default '''group''' for '''user suraj'''.

As we know the default or '''primary group''' for '''user suraj''' is '''CSE'''.

Let me check that.
|-
|| Type id [Enter]
|| Type the '''id '''command.
|-
|| Highlight in the output
|| Notice, our current '''group''' is now '''CSE.'''
|-
|| Type exit [Enter]
|| Exit from the '''group CSE '''login session
|-
|| Type exit [Enter]
|| Exit from the '''group music_club '''login session
|-
|| Type exit [Enter]
|| Now exit from the '''user login session'''.
|-
|| spoken@spoken:
|| We are back to the '''user session spoken'''
|-
|| Slide 12A
|| A note on '''group password''':

* If the '''user''' is '''root''', he or she will not be prompted for a '''password'''.
* If there is no '''group password''' set and the '''user''' is not listed as a member of the '''group'''.
* Then the '''user''' will be denied '''access'''

|-
|| Slide 12B
|| '''Non-root users''' will be prompted for a '''group password'''

* if the '''user''' is not listed as a '''group member'''
* and the '''group''' has a '''password'''.

|-
|| Slide 12D
|| 
* Notice that more than one person is permitted to know the '''group password. '''
* So, '''group password''' has an inherent security problem.
* However, '''groups''' are a useful tool for permitting cooperation between different '''users'''.

|-
|| Switch to the terminal
|| Switch to the '''terminal''', in which we have logged in as a '''root user.'''
|-
|| Type exit [Enter]
|| Exit from the '''root user.'''
|-
|| 
|| This brings us to the end of this tutorial.

Let us summarize.
|-
|| Slide 13
Summary
|| In this tutorial we learnt about-

* '''newgrp command'''
* Securing a '''group '''with '''password'''
* '''Login''' to a '''group''' as a '''group member'''
* '''Login''' to a''' group '''as a '''non-member'''

|-
|| Slide 14A Assignment 
|| As an assignment-

# Create a new '''group accounts''' for the college '''database'''.
# Give a suitable '''password''' for the '''group''' created.
# Create two '''users: rekha''' and '''sheetal'''.

|-
|| Slide 14B Assignment 
|| 
# Check details of '''user rekha''' using the '''command id'''.
# Add '''rekha''' as a member of the '''group'''.
# Check how the '''user rekha''' can login to the '''group accounts.'''

|-
|| Slide 14C Assignment 
|| 
# Check how the '''user sheetal''' can login to the '''group accounts.'''
# At every step, check the details of '''group accounts '''from '''/etc/gshadow''' file.

|-
|| Slide 15 About Spoken Tutorial project
|| The video at the following link summarises the Spoken Tutorial project.

Please download and watch it.
|-
|| Slide 16

Spoken Tutorial workshops
|| The Spoken Tutorial Project team conducts workshops using spoken tutorials and gives certificates.

For more details, please write to us.
|-
|| Slide 17
Forum for specific questions:
|| Pls post your timed queries in this Forum.
|-
|| Slide 18
Acknowledgement
|| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at this link.
|-
|| 
|| The script has been contributed by Antara.

And this is Praveen from IIT Bombay signing off.

Thanks for joining.
|-
|}