Linux-for-Sys-Ads/C2/Assigning-groups-on-user-creation/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Hello and welcome to the spoken tutorial on Assigning Groups on User Creation in Linux. |
| 00:08 | In this tutorial we will learn about
Creating a user group /etc/group file |
| 00:17 | Assigning groups to users at the time of account creation |
| 00:22 | We will do this through some examples. |
| 00:25 | To record this tutorial, I am using Ubuntu Linux 16.04 Operating System |
| 00:32 | To practice this tutorial,
you should have gone through Linux System Administration tutorials on this website. |
| 00:40 | you must have root access to your computer. |
| 00:44 | What is a group in Linux? |
| 00:47 | We can understand group as a collection of users. |
| 00:51 | In a college system, a group can be different departments like CSE, Electrical etc. |
| 00:58 | Groups can also be different clubs like music club, sports club, literature club, etc. |
| 01:06 | Linux supports two types of groups.
Primary group and Supplementary group |
| 01:12 | Every user must belong to one and only one primary group. |
| 01:17 | This is the default group for the user when the user logs in. |
| 01:22 | For example: a student must belong to one and only one department. |
| 01:28 | A user can be a member of more than one group. |
| 01:32 | Those groups are called supplementary groups. |
| 01:36 | These groups are assigned to the user, to provide him additional access to resources. |
| 01:43 | More on access mechanism or permission will be discussed in subsequent tutorials. |
| 01:50 | Let’s take an example. User radha belongs to the CSE department. |
| 01:56 | She is also a member of the music club and sports club. |
| 02:01 | In this scenario, CSE is the primary group for radha. |
| 02:05 | And she is a member of two supplementary groups - music club and sports club. |
| 02:12 | Let’s create this scenario in our system. |
| 02:16 | First, we will create group CSE. |
| 02:19 | And we will use addgroup command in order to create this group. |
| 02:24 | Open the Terminal by pressing Ctrl, Alt and T keys simultaneously on the keyboard. |
| 02:32 | Now, we should login as superuser or root user. |
| 02:37 | To do so type: sudo space su and press Enter. |
| 02:44 | Type the admin password and then press Enter. |
| 02:48 | Notice, our login prompt has changed to a hash symbol. |
| 02:53 | This indicates that we are in the root user mode. |
| 02:57 | Here onwards, please remember to press the Enter key after typing each command. |
| 03:03 | Now type addgroup space cse |
| 03:08 | This will create group cse. |
| 03:12 | Linux automatically allocates a Unique ID for each group that is created. |
| 03:18 | Here, GID, that is Group ID is 1002. |
| 03:22 | Alternatively, we can mention a GID of our choice. |
| 03:28 | For this, we need to use hyphen gid option along with the addgroup command. |
| 03:35 | GIDs in the range of 0 to 999 are reserved for the system users. |
| 03:42 | So, always choose a number greater than or equal to 1000 as GID |
| 03:49 | Let’s us create a group Music_club with the GID 1012. |
| 03:55 | On the terminal type:
addgroup space hyphen gid 1012 space Music underscore club |
| 04:06 | Here type M is in capital letter. |
| 04:10 | Notice, it is showing some error. |
| 04:13 | Actually, we should have written m in lowercase letter.
Let’s try that. |
| 04:19 | Press the Up arrow key to get the previously executed command. |
| 04:24 | Change capital M to m in lowercase letter. |
| 04:30 | The command is working now. |
| 04:32 | So, always remember to use lowercase letters while writing group names. |
| 04:38 | Similarly let’s create another group sports underscore club. |
| 04:43 | This time no need to mention the GID. |
| 04:48 | Now we have three groups cse, music underscore club and sports underscore club. |
| 04:55 | How can we check the details of the created group?
Type cat space /etc/group |
| 05:05 | There will be an entry in this file for every user on the system. |
| 05:11 | Each line has four fields separated by a colon symbol. |
| 05:16 | The first field is the name of the group. |
| 05:19 | The second field is the encrypted password for the group. |
| 05:24 | Third field shows the GID as a number. |
| 05:28 | Fourth field contains the list of users that belong to that group separated by commas. |
| 05:35 | This list contains all users who have this group as a secondary group. |
| 05:41 | We can see the entries for cse, music underscore club and sports underscore club groups. |
| 05:49 | Notice, music underscore club has Gid 1012 which we mentioned during group creation. |
| 05:57 | Here, the fourth field is empty for all the groups. |
| 06:02 | This is because there are no members in these groups, as of now. |
| 06:07 | The password field is x. |
| 06:10 | We will discuss about the password field and list of members field in detail, in a separate tutorial on groups. |
| 06:18 | Now, how can we specify the primary and supplementary groups while creating the user?
Let us see an example. |
| 06:26 | To specify that user radha belongs to the primary group cse, type:
adduser space hyphen ingroup space cse space radha |
| 06:40 | Type the password as pass underscore radha and press Enter. |
| 06:46 | Retype the same password and press Enter. |
| 06:50 | Type name as Radha with capital R.
And proceed as we have done before. |
| 06:59 | We have successfully created user radha with primary group cse. |
| 07:05 | So, you should use ingroup option to specify primary group’s name while creating the user. |
| 07:13 | As we know, radha is a member of music underscore club. |
| 07:17 | So music underscore club will be the supplementary group for the user radha. |
| 07:23 | Type adduser space radha space music underscore club |
| 07:31 | Remember.
To add supplementary groups using adduser command, you should have an existing user. |
| 07:38 | Here, we have first created the user radha. Then added radha to the supplementary group using adduser command. |
| 07:46 | If you need to specify that radha is also a member of sports club type:
adduser space radha space sports underscore club |
| 07:59 | Let’s check user radha’s details using id command. |
| 08:04 | Type id space radha |
| 08:08 | Notice, User radha is in group cse which has GID 1002 |
| 08:15 | That is the primary group for radha. |
| 08:19 | Next, there is the list of groups, where user radha is member of. |
| 08:25 | Along with primary group cse, radha is also a member of two supplementary groups music underscore club and sports underscore club. |
| 08:35 | Now let’s check our /etc/group file for the entry of radha |
| 08:42 | Type: grep space radha space /etc/group |
| 08:49 | Notice, you can see user radha is the member of groups music underscore club and sports underscore club |
| 08:58 | But not as a member of the primary group that is cse. |
| 09:03 | So the group file will list only the supplementary groups in which the user is associated. |
| 09:10 | Check the /etc/passwd file for the details of the username radha. |
| 09:17 | Type grep space radha space /etc/passwd |
| 09:25 | Notice, the fourth field is 1002 |
| 09:29 | It is the GID for the group cse. |
| 09:33 | It is the primary group for radha. |
| 09:36 | So, remember /etc/passwd shows primary group ID for a user |
| 09:43 | /etc/group file shows list of usernames who have the group as a supplementary group |
| 09:51 | Command id space username shows the details of both primary and supplementary groups |
| 09:59 | You can also specify the group id instead of group’s name while creating the user. |
| 10:05 | Let us create a user suraj and assign him to the group cse using the gid. |
| 10:12 | We know group cse has GID 1002 |
| 10:17 | So type: adduser space hyphen gid space 1002 space suraj |
| 10:26 | You should use hyphen gid option to specify the group ID. |
| 10:32 | Use pass underscore suraj as the password |
| 10:37 | Retype the password
Full Name as Suraj with S in capital letter. |
| 10:45 | Proceed as we have done for the previous users. |
| 10:49 | We have successfully created user suraj with primary group cse. |
| 10:55 | To exit from the root user access, type exit |
| 11:00 | This brings us to the end of this tutorial.
Let us summarize. |
| 11:05 | In this tutorial we learnt about-
Creating primary group |
| 11:10 | Assigning user to the primary group |
| 11:13 | Assigning user to the supplementary group /etc/group file |
| 11:19 | Assigning groups to users at the time of account creation |
| 11:24 | As an assignment- Create two groups: cultural , literature |
| 11:30 | Now create a user ajay with Home directory as /home/ajay underscore dir |
| 11:39 | User id as 1090 |
| 11:42 | Primary group as cultural |
| 11:45 | Supplementary group as literature |
| 11:49 | Add comments "Native: Mumbai" |
| 11:52 | Use the command id to check the user details |
| 11:56 | Check the details of user ajay in /etc/passwd and /etc/group files |
| 12:05 | The video at the following link summarises the Spoken Tutorial project.
Please download and watch it. |
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| 12:27 | Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. |
| 12:33 | The script has been contributed by Antara and this is Praveen from IIT Bombay signing off.
Thank you for joining. |
