![creating and managing groups in linux creating and managing groups in linux](https://tekneed.com/wp-content/uploads/2024/06/creating-and-managing-groups-in-linux-1.png)
How to Create Groups in Linux – Introduction
Hello everyone! Today, we’re diving into an essential topic for any Linux user: how to create and manage groups. Understanding groups is crucial for managing permissions and access on a Linux system.
You can also watch this lesson’s video tutorial here.
Before I continue, if you intend to write the certification exam,
you can get our exam practice or preparation questions using this link, or contact us on info@tekneed.com.
So, let’s get started!
Types of Groups in Linux
In Linux, there are two types of groups: primary groups and secondary (or supplementary) groups.
Primary Groups
A primary group is created by default whenever a user is created. The primary group has the same name as the user. For example, if you create a user named john
, a primary group called john
is also created, and the user john
is automatically added to this group.
Secondary Groups
Secondary groups are additional groups that users can be added to, which are not created by default. These groups are usually created manually by the user or the system administrator.
Understanding Group Attributes
When groups are created, their information is stored in the /etc/group
file. Let’s explore this file:
cat /etc/group
![how to create groups in linux - 1](https://tekneed.com/wp-content/uploads/2024/06/how-to-create-groups-in-linux-1-1024x575.png)
You will see a list of groups with their attributes. Let’s create a new group to understand this better. To create a group, use the groupadd
command followed by the name of the group:
groupadd sales
If you check the /etc/group
file again, you’ll see the new sales
group listed. Here’s a breakdown of the attributes:
![how to create groups in linux - sales](https://tekneed.com/wp-content/uploads/2024/06/how-to-create-groups-in-linux-sales-1024x486.png)
- Group Name:
sales
- Group Password: Represented by an
x
, stored in/etc/gshadow
- Group ID (GID): A unique identifier for the group, for example,
1010
- Group Members: Users who belong to this group
Adding Users to Groups
To add users to a group, we use the usermod
command. For example, to add a user named lisa
to the sales
group:
usermod -aG sales lisa
Here, -aG
appends the user to the group without removing them from other groups.
![how to create groups in linux - add lisa](https://tekneed.com/wp-content/uploads/2024/06/how-to-create-groups-add-lisa.png)
If you check the /etc/group
file again, you will see lisa
listed under the sales
group. Similarly, you can add another user, tekneed
, to the same group:
usermod -aG sales tekneed
Now, let’s verify:
cat /etc/group
![2 users in sales group](https://tekneed.com/wp-content/uploads/2024/06/2-users-in-sales-group.png)
You should see both lisa
and tekneed
in the sales
group.
How to Create Groups in Linux – Red Hat Enterprise Linux
Now, let’s see how to create groups in linux, specifically in Red Hat.
Creating a Primary Group
When you create a user, a primary group is automatically created. For example:
useradd ola
Check the /etc/group
file:
cat /etc/group
![how to delete groups in linux - hr](https://tekneed.com/wp-content/uploads/2024/06/how-to-delete-groups-in-linux-hr.png)
You’ll see the ola
group created with a unique GID of 1012.
Creating a Secondary Group
To create a secondary group, use:
groupadd hr
Verify the creation:
cat /etc/group
![how to create groups in linux - showing all groups](https://tekneed.com/wp-content/uploads/2024/06/how-to-create-groups-in-linux-showing-all-groups.png)
You should see the hr
group listed. It has a unique group ID of 1013.
Adding Users to a Secondary Group
The command used to add users to a group is usermod.
Take your time to look through the help manual of the usermod command.
![add users to group - help](https://tekneed.com/wp-content/uploads/2024/06/add-users-to-group-help.png)
Note: always use the append option when adding users to a group, so as not to overwrite the existing users in the group.
usermod -aG sales tekneed
Check the group file:
cat /etc/group
![how to create groups in linux - showing all groups](https://tekneed.com/wp-content/uploads/2024/06/how-to-create-groups-in-linux-showing-all-groups.png)
However, in RHEL 9; users do not get overwritten even when the append option is not used.
usermod -G sales tekneed2
Check the group file:
cat /etc/group
![adding users to groups on RHEL9 - not need append](https://tekneed.com/wp-content/uploads/2024/06/adding-users-to-groups-on-RHEL9-not-need-append.png)
Deleting a Group
To delete a group, use the groupdel
command:
groupdel hr
Verify the deletion:
cat /etc/group
![](https://tekneed.com/wp-content/uploads/2024/06/deleted-user-HR.png)
Modifying a Group
To modify a group, use the groupmod
command. For example, to change the name of a group:
groupmod -n newname oldname
Password Management
User passwords are stored in the /etc/shadow
file, while group passwords (though rarely used) are stored in /etc/gshadow
. For consistency when editing user or group information, use commands like vipw
for users and vigr
for groups to ensure both the password and shadow files are updated.
Editing User and Group Files
To edit user information safely:
sudo vipw
To edit group information:
sudo vigr
These commands ensure consistency between the /etc/passwd
and /etc/shadow
files, or the /etc/group
and /etc/gshadow
files.
How to Create Groups in Linux – Ubuntu
Adding a User
This has been comprehensively explained in our previous lesson.
To add a new user in Ubuntu, use the useradd
command followed by the username. For instance, to create a user named ola
, execute:
useradd ola
To set a password for ola
, use:
passwd ola
You can verify the creation of the user by viewing the contents of the /etc/passwd
file:
cat /etc/passwd | grep ola
Similarly, check the group file to confirm the creation of the user’s primary group:
cat /etc/group | grep ola
When a user is created, a primary group with the same name is also created. This primary group is crucial for managing user permissions and file ownership.
Creating Secondary Groups
In Linux, secondary groups are often used to manage additional permissions and access rights. On how to create groups in linux, use the groupadd
command:
groupadd finance
Verify the creation of the group by checking the /etc/group
file:
cat /etc/group | grep finance
Adding Users to Groups
Users can be added to secondary groups using the usermod
command. This command allows for various modifications, including adding users to supplementary groups:
usermod -aG finance ola
Here, the -a
option appends the user to the group without removing them from other groups, and the -G
option specifies the supplementary group.
Verify the user’s group membership:
cat /etc/group | grep finance
To add multiple users to a group, repeat the command with different usernames:
usermod -aG finance tekneed
usermod -aG finance tekneed2
Note: If you do not use the -a
option, it may remove the user from other supplementary groups.
Modifying and Deleting Groups
To modify group properties, use the groupmod
command. For instance, to rename a group:
groupmod -n newgroupname oldgroupname
To delete a group, use the groupdel
command:
groupdel finance
Verify the deletion:
cat /etc/group | grep finance
Editing Configuration Files Directly
While commands like usermod
and groupmod
are preferred for safety, direct editing of configuration files is possible for experienced users. The primary files to be aware of are:
/etc/passwd
: Stores user account information./etc/shadow
: Stores encrypted user passwords./etc/group
: Stores group information./etc/gshadow
: Stores secure group information.
To ensure consistency, always use the vipw
command for editing user information and vigr
for group information. These commands lock the files, preventing concurrent modifications.
For example, to safely edit the /etc/passwd
file:
vipw
And for the /etc/group
file:
vigr
After making changes, you may also need to edit the shadow files to ensure consistency:
vipw -s
vigr -s
Conclusion
Understanding how to create groups in Linux is fundamental for system administration. Groups help in organizing users and managing permissions efficiently. Understanding how to add, modify, and delete users and groups, as well as ensuring consistency in configuration files, is essential for maintaining a secure and well-organized system. Practice these commands, and you’ll become proficient in handling user groups on any Linux system.
For those preparing for the Red Hat Certified System Administrator (RHCSA) exam, mastering these concepts is crucial. Stay tuned for more tutorials, and don’t forget to subscribe, like, and share!
Happy learning!
Feel free to leave your comments or questions below. If you’re preparing for certification exams, check out the practice questions linked in the description. Your feedback and engagement help us create more valuable content.
We believe that by the end of this tutorial, you now know how to create groups in linux; on both RHEL and Ubuntu systems.
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