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In Linux, multiple users can use the same system at the same time. In order to manage these users, Linux assists you with a mechanism known as Groups. In simple terms, Groups are a collection of several users.
This article will help you to achieve a decent grip over the concept of groups and how to implement them.
Prerequisites
- A system with Linux
- Terminal window access
What does a User group mean in Linux?
There are various users with several distinct roles and responsibilities. There are certain restrictions associated with obtaining access to files and folders. With pre-set permissions, Groups in Linux help you to categorize the users. Instead of granting access to the individual user accounts, you can simply add the user to the group and grant permissions. Easy, right?
Additionally, there are two categories of groups, namely, the primary group and the secondary group. Here is an elaboration regarding both of them.
- Primary group: A primary group is automatically created when a user with a unique user ID is created.
- Secondary group: A secondary group is created by using commands. You can change the group IDs of the users and add them to this group later.
Read further to understand how to create a group first.
How to create a group in Linux?
Using the following command:
sudo groupadd newgroup
You can allocate any name to the group you create.
Moving further, the next up is, how to add a user to the group.
How do you add a user to a group?
We have bifurcated the topic into sub-parts. Read on.
How to add existing users to the existing group?
First method:
Use the adduser command, here is the syntax:
sudo adduser username newgroup
Second method:
To use the useradd command as shown below:
sudo useradd –G newgroup username
Third method:
Use the usermod command:
sudo usermod –a –G groupname username
There are two options, the -append option and the -group option. They are used by the usermod command to append the users with a group. Without the append option, you may be discarded from other groups.
How do you create a user and then add it to a group?
Follow this simple command to create a user and immediately add him to an already existing group:
sudo useradd –G groupname newuser
Now, simply add a password by using the following command:
sudo passwd newuser
That’s it!
How to add a user to various groups at the same time?
You can complete this task with the usermod command. Write the name of various groups in one command as mentioned below:
sudo usermod –a –G newgroup, newgroup1, newgroup2, username
How to change the User’s Primary Group?
Until now you have studied the commands related to the secondary groups. As you have learned above, that the primary group is automatically generated while creating a user. Therefore, the username is the same as the primary group.
If you are hunting for a way to change the primary group, follow this command:
sudo usermod -g newgroup username
Here, -g signifies the primary group. Previously, we used -G, which is used for the secondary groups. Additionally, as the user can only inhibit one primary group, therefore, the initial username that you had set would no longer be primary.
How to remove a user?
Use the gpasswd tool, if you want to eliminate a user from a particular group. This is how you use it:
sudo gpasswd -d username newgroup
Furthermore, you can use the gpasswd tool to perform several administrative operations. For instance, to set a password, to access the group resources or to define group administrators.
How can you list groups?
Follow this command in order to view a list of groups on your screen:
sudo nano /etc/groups
Moving on, if you want to delete a group, use the below-mentioned command.
How do you delete a group?
sudo groupdel newgroup
If you want to view which group belongs to which user, type this command:
groups username
There is a different approach to achieve the same task too. You can use the user ID and group ID to know the name of the group to which a user belongs!
Use this command:
id username
In case you do not write the name of the username, the command automatically displays the current logged-in user.
Moving on, there are many group names assigned to the groups by default in Linux. Here is a list for you:
adm: The user can keep a check on the Linux system logs.
Ipadmin: The user can easily carry out printer configuration.
cdrom: The optical drive can be easily mounted
wheel: You can easily grant sudo-like privileges.
plugdev: External storage devices can be easily accessed by the user.
Conclusion
This article provided basic knowledge about the Linux groups. We hope that the mentioned commands to add or remove users in a group helped you to sort out your queries.
Keep practicing the commands to build a firm grip over the topic.
