Learn how to effortlessly add a user to a group in Linux systems and effectively remove them in this comprehensive tutorial. Our expert guide also covers essential techniques to create, delete, and list groups on your Linux machine. Master the process with our step-by-step instructions today.
In Linux, groups serve as units of organization and administration for user accounts. Their main function is to establish a set of privileges, including reading, writing, and executing permissions, for a specific resource that can be shared among group members.
Linux operating systems consist of two distinct categories of groups:
- The Primary group: After a user generates a file, its group defaults to the user’s primary group, typically sharing the same name as the user. The
/etc/passwdfile retains the details of the user’s primary group.
- Secondary or supplementary group: If you wish to assign particular file permissions to a group of users, adding those users to a group can be helpful. By way of illustration, if you add a particular user to the docker group, that user will obtain the group’s access privileges and become capable of executing docker commands.
The primary group of a user is unique, while they can be a member of multiple secondary groups.
Adding a user to a group is a privilege reserved for the root user or users with
How to Add an Existing User to a Group
To assign a user to a supplementary group, utilize the command “
usermod -a -G” and specify the group name and the user’s name:
sudo usermod -a -G groupname username
To illustrate, if you want to include the user “
trioguide” in the sudo group, you can execute the subsequent command:
sudo usermod -a -G sudo trioguide
When adding a user to a new group, it is important to include the
-a (append) option to avoid removing the user from any groups not explicitly listed after the
-G option. If the user or group does not exist, the
usermod command will display a warning message. Successful execution of the command does not yield any output.
How to Add an Existing User to Multiple Groups in One Command
To add a current user to multiple secondary groups simultaneously using a single command, utilize the “
usermod” command and specify the “
-G” option followed by the group names separated by commas:
sudo usermod -a -G group1,group2 username
How to Remove a User From a Group
If you want to exclude a user from a group, utilize the
gpasswd command and specify the -d option.
In this instance, we are eliminating the username of a user from a particular group known as groupname:
sudo gpasswd -d username groupname
How to Create a Group
groupadd command can be utilized to form a new group by specifying the desired group name:
sudo groupadd groupname
How to Delete a Group
To remove a group that already exists, you can use the
groupdel command and specify the name of the group:
sudo groupdel groupname
How to Change a User’s Primary Group
To modify the primary group of a user, utilize the
usermod command and then add the
sudo usermod -g groupname username
The user “
trioguide” will have their primary group changed to “
developers” in the given example:
sudo usermod -g developers trioguide
How to Create a New User and Assign Groups in One Command
useradd command will generate a fresh user account designated as “
alex“. This user account will have the users group as its primary group and the wheel and
developers groups as secondary groups.
sudo useradd -g users -G wheel,developers alex
Display User Groups
If you want to view comprehensive details about a user, including their group memberships, you can utilize the “
id” command and provide the user’s username as the argument:
Printing information about the currently logged-in user is possible by omitting the username in the command. To verify the user “
trioguide“, we can execute the command:
Output:uid=1000(trioguide) gid=100(users) groups=100(users),10(wheel),95(storage),98(power),990(libvirt),993(docker),999(kvm)
Based on the displayed information, it is apparent that the user’s primary group is “
users” and it is affiliated with supplementary groups such as “
docker“, and “
To exhibit the additional groups of a user, utilize the “
Output:wheel storage power users libvirt docker kvm
groups command is executed without specifying a username, it will display the groups associated with the user who is currently logged in.
This tutorial has demonstrated the process of adding a user to a group, which can be implemented on various Linux distributions such as Ubuntu, CentOS, RHEL, Debian, and Linux Mint by utilizing identical commands. If you have any inquiries, please don’t hesitate to leave a comment.