This article covers how you can easily find out which groups a user belongs to in Ubuntu. Also we shared how to list all groups in a system, list members of a group, add and remove a user from the group. For information about adding/removing users in a system, visit our guide on how to add and remove users on Ubuntu .
Adding a user to an existing group is one of the typical tasks of a Linux administrator.
A group is a collection of users.
The main purpose of the group is to define a set of privileges to their members within the group.
To find out if a user has sudo access is by checking if the said user is member of the sudo group.
If you see the group 'sudo' in the output, the user is a member of the sudo group and it should have sudo access.
In order to list groups on Linux, you have to execute the "cat" command on the "/etc/group" file.
When executing this command, you will be presented with the list of groups available on your system.
To login as Sudo on Ubuntu:
1. Open a terminal Window. Press Ctrl + Alt + T to open the terminal on Ubuntu.
2. To become root user type: sudo -i. sudo -s.
3. When promoted provide your password.
4. After successful login, the $ prompt would change to # to indicate that you logged in as root user on Ubuntu.
What is /etc/passwd file?
"/etc/passwd" is a text file containing every user information that is required to login to the Linux system. It maintains useful information about users such as username, password, user ID, group ID, user information, home directory and shell.
To find out which groups a user belongs to in Linux:
1. groups: Show All Members of a Group.
2. id: Print user and group information for the specified username.
3. lid or libuser-lid: It display user's groups or group's users.
4. getent: Get entries from Name Service Switch libraries.
5. compgen: compgen is bash built-in command and it will show all available commands for the user.
6. members: List members of a group.
7. /etc/group file: Also, we can grep the corresponding user’s groups from the /etc/group file.
What is Wheel Group in Linux?
The wheel group is a special user group used on some Unix systems, mostly BSD systems, to control access to the su or sudo command, which allows a user to masquerade as another user (usually the super user). Debian-like operating systems create a group called sudo with purpose similar to that of a wheel group.
Types of groups in Linux:
1. Primary Group - The primary group is the main group associated with the user account. Each user must be a member of a single primary group.
2. Secondary Group - The secondary or supplementary group is used to grant additional rights to the user. Each user can become a member of multiple secondary groups.