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

Time	Narration
00:01	Hello and welcome to the spoken tutorial on Group Password and Login.
00:08	In this tutorial we will learn about newgrp command
00:14	Securing a group with password
00:17	Login to a group as group member
00:20	Login to a group as non-member
00:24	We will do this through some examples.
00:28	To record this tutorial, I am using Ubuntu Linux 16.04 OS
00:35	To practice this tutorial, you should have gone through the Linux System Administration tutorials on this website and
00:45	you must have root access to your computer.
00:49	Earlier in the series, we had created two users, suraj and testmod.
00:56	Let us check the status of these users.
01:00	Open the Terminal by pressing Ctrl, Alt and T keys simultaneously on the keyboard.
01:09	First, login as superuser or root user.
01:16	Here onwards, please remember to press the Enter key after typing each command.
01:23	Now type id space suraj
01:28	The output indicates that Suraj belongs to primary group CSE.
01:34	He is not a member of any additional supplementary group.
01:39	Now type id space testmod
01:44	The output shows that user testmod belongs to primary group Electronics.
01:51	He is also a member of two supplementary groups - music_club and literature_club
02:00	For this demonstration, we will use the group music_club.
02:06	We will first check the details of the group music_club.
02:11	Type the command as shown
02:15	The output shows the details of the group music_club.
02:20	Here the value of the second field i.e. the password field is x.
02:26	So, for password details we have to refer to the /etc/gshadow file.
02:34	Type the command as shown.
02:38	Here, the value of the second field is an exclamation mark.
02:43	This means that the password is either invalid or not set.
02:49	Also, we can see that testmod is listed as a member of the group music_club.
02:56	It is clear that the group music_club does not have a valid password.
03:03	Now, let us check how a member like testmod and a non-member like suraj can login to this group.
03:12	For login to a group, we will use newgrp command.
03:17	The newgrp command is used to change the current group ID during a login session.
03:24	The syntax of newgrp command is- newgrp space hyphen space Newgroup
03:33	Here, hyphen and Newgroup are optional parameters
03:39	Newgroup is either a group ID number or a group name located in /etc/group.
03:47	Then newgrp refers to the file /etc/passwd for the particular entry of the user.
03:57	And changes the current group to the default group listed in the file /etc/passwd for the user.
04:07	Optional hyphen flag re-initializes the user's environment as though the user has just logged in.
04:16	Otherwise, the current environment remains unchanged.
04:21	For the demonstration in this tutorial, we will always use the hyphen flag.
04:27	Let me try to login to the group music_club as a member, say testmod.
04:34	For this we have to login to user account testmod
04:39	We will open a new terminal window for this.
04:43	Right click on the terminal.
04:45	From the pop-up select Open Terminal.
04:50	From this point onwards, we will use both these terminals.
04:55	We will switch from one terminal to another terminal for demonstration purpose.
05:01	In the new terminal we are logged in as user spoken.
05:06	Now, let me login as user testmod.
05:12	Then type id
05:15	music_club is listed as one of the supplementary groups.
05:21	In order to login to group music_club, type- newgrp space hyphen space music underscore club
05:33	The command has executed without any error.
05:37	Type id once again.
05:40	Notice now that our current group is music_club.
05:45	Earlier it was Electronics.
05:49	So, our current group has changed.
05:51	We are logged in to music_club.
05:57	This login session will continue until we execute the exit command.
06:03	So, let’s now type exit command
06:07	Recall the id command
06:10	Now, our current group is Electronics.
06:14	To exit from this user login session, type exit.
06:19	Notice that the terminal prompt has changed.
06:22	Currently, we are logged in as user spoken.
06:27	Now, let’s see how a non-member like suraj can login to the group music_club.
06:35	Let us try to use the same newgrp command for this purpose.
06:40	Let me login as user suraj
06:46	We are logged in as suraj.
06:50	Type id
06:52	Notice that our current group is CSE.
06:56	And there are no supplementary groups listed.
07:00	So, it's clear that suraj is not member of the group music_club.
07:07	Let me login to group music_club
07:12	It is asking the password. But we haven’t set any valid password for the group music_club.
07:20	We cannot login to the group music_club.
07:24	Press Control and D keys together to exit the group login process.
07:31	Now exit from the user login session
07:36	We are back to the user account spoken.
07:40	From this we understand that if a group does not have a valid password set,
07:47	then only a group member can use newgrp - group command to login to the group.
07:55	Non-members cannot login to the group.
07:59	So, let us secure the group access with a password.
08:04	Superuser or group administrator can use gpasswd space Newgroup to set or change the password of a group.
08:15	Newgroup is either a group ID or a group name that you have to write in the command.
08:22	We will discuss about the group administrator in a separate tutorial later.
08:27	Let us now try to set the password as superuser.
08:32	Switch to the terminal in which we have logged in as a root user.
08:37	To set the password for the group music_club, type gpasswd space the name of the group that is music underscore club
08:49	Type group password as pass underscore music Press Enter
08:56	Retype the same password and press Enter.
09:01	Now we will repeat the login process to the group music_club as a member and also as a non-member.
09:09	Switch to the other terminal where we have logged in as user spoken
09:15	Let me login as user testmod.
09:20	Now login to the group music_club The command has executed without any error.
09:29	Type id
09:31	Notice that our current group is now music_club.
09:36	So what do we understand from this?
09:39	Even though the group has a password, group members will not be prompted to provide the password while logging in.
09:48	Exit from the group login session,
09:51	Exit from the user testmod.
09:55	We are back to the user prompt spoken.
09:59	Now, suraj is a non-member for the group music_club.
10:05	Let’s see if suraj can use the same newgrp command to login to the group.
10:11	login as user suraj
10:15	Type the id command
10:18	As we know suraj is not a member of any supplementary group.
10:23	Now login to the group music_club,
10:28	It is asking for a password.
10:30	Type pass underscore music which we set just now.
10:36	The command has executed without any error.
10:40	Type id command
10:43	Notice, our current group is now music_club.
10:48	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.
10:59	To switch back to your original login group, type newgrp
11:05	Now, newgrp command is used without any argument.
11:10	It should change the current group to the default group for user suraj.
11:16	As we know the default or primary group for user suraj is CSE. Let me check that.
11:23	Type the id command.
11:26	Notice, our current group is now CSE.
11:30	Exit from the group CSE login session
11:34	Exit from the group music_club login session
11:39	Now exit from the user login session.
11:43	We are back to the user session spoken
11:47	A note on group password:
11:50	If the user is root, he or she will not be prompted for a password.
11:56	If there is no group password set and the user is not listed as a member of the group.
12:02	Then the user will be denied access
12:06	Non-root users will be prompted for a group password
12:10	if the user is not listed as a group member and the group has a password.
12:17	Notice that more than one person is permitted to know the group password.
12:23	So, group password has an inherent security problem.
12:29	However, groups are a useful tool for permitting cooperation between different users.
12:36	Switch to the terminal, in which we have logged in as a root user.
12:41	Exit from the root user.
12:44	This brings us to the end of this tutorial. Let us summarize.
12:50	In this tutorial we learnt about- newgrp command
12:55	Securing a group with password
12:58	Login to a group as a group member
13:01	Login to a group as a non-member
13:05	As an assignment- Create a new group accounts for the college database.
13:12	Give a suitable password for the group created.
13:16	Create two users: rekha and sheetal.
13:21	Check details of user rekha using the command id.
13:26	Add rekha as a member of the group.
13:30	Check how the user rekha can login to the group accounts.
13:35	Check how the user sheetal can login to the group accounts.
13:40	At every step, check the details of group accounts from /etc/gshadow file.
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14:18	The script has been contributed by Antara. And this is Praveen from IIT Bombay signing off. Thanks for joining.

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