Group Management in Linux

There are 2 categories of groups in the Linux operating system i.e. Primary and Secondary groups. The Primary Group is a group that is automatically generated while creating a user with a unique user ID simultaneously a group with an ID the same as the user ID is created and the user gets added to the group and becomes the first and only member of the group. This group is called the primary group. A secondary group is a group that can be created separately with the help of commands and we can then add users to it by changing the group ID of users.

How to Create/Add Users in Linux

Creating a Secondary Group

The below command created a group with the name provided. The group while creating gets a group ID and we can get to know everything about the group as its name, ID, and the users present in it in the file "/etc/group".

groupadd group_name

Example:

groupadd Group1

Setting the Password for the Group

Below command is used to set the password of the group. After executing the command, we have to enter the new password which we want to assign to the group. The password has to be given twice for confirmation purposes.

gpasswd group_name

Example:

gpasswd Group1

Command to Display the Group Password File:

To access information about groups and their passwords, you can view the password file, /etc/gshadow. However, keep in mind that this file is not intended for regular viewing. To gather more comprehensive information about groups.

cat /etc/gshadow

Adding a User to an Existing Group

To add a user to an existing group, you can utilize the usermod command. By specifying the group name, you can add a user to the desired group. However, note that when a user is added to a new group, they are automatically removed from their previous groups.

usermod -G group_name  username

usermod -G group1 John_Doe

Note:

If we add a user to a group then it automatically gets removed from the previous groups, we can prevent this by the command given below.

Command to Add User to Group Without Removing from Existing Groups

This command is used to add a user to a new group while preventing him from getting removed from his existing groups.

usermod -aG *group_name  *username

Example:

usermod -aG group1 John_Doe

Command to Add Multiple Users to a Group at once

To add multiple users to a group simultaneously, you can utilize the gpasswd command with the -M option. This command allows you to specify a list of usernames separated by commas.

gpasswd -M *username1, *username2, *username3 ...., *usernamen *group_name

Example:

gpasswd -M Person1, Person2, Person3 Group1

Deleting a User from a Group

Below command is used to delete a user from a group. The user is then removed from the group though it is still a valid user in the system but it is no longer a part of the group. The user remains part of the groups which it was in and if it was part of no other group then it will be part of its primary group.

gpasswd -d *username1  *group_name  

Example:

gpasswd -d Person1  Group1

Command to Delete a Group

To delete a group from the system, use the groupdel command. This action removes the group while retaining the users who were members of the group. They will revert to their primary groups if they are not part of any other groups.

groupdel *group_name

Example:

groupdel  Group1

Conclusion

In this article we have discussed group management in Linux which involves creating and managing primary and secondary groups, setting group passwords, adding and removing users, and deleting groups. We also discussed effectively utilizing these commands and techniques, administrators can organize user accounts, assign appropriate access permissions, and ensure a secure and efficient Linux system.