How to List Groups on Linux

Introduction

Before we begin talking about how to list groups on Linux, let's briefly understand – What is a Group ?

A group on Linux is a gathering of users. The fundamental goal of groups is to specify a set of privileges for a certain resource that may be shared across the users inside the group, such as read, write, or execute access. To take advantage of the rights granted by an existing group, users can be added to it.

In this tutorial, we will show you how to list groups on Linux. We will also address a few FAQs on how to list groups on Linux.

Advantages of Groups

1. Access Control: Groups enable efficient management of user access to files and resources.
2. Simplified Permissions: Setting permissions at the group level reduces administrative efforts for granting/restricting access.
3. Enhanced Security: Assigning users to appropriate groups improves security by ensuring only authorized access to sensitive data.
4. Efficient Collaboration: Groups facilitate teamwork by allowing multiple users to access and work on shared files simultaneously.
5. Streamlined Administration: Managing permissions and user accounts becomes easier as group membership simplifies administrative tasks.

Linux Groups

A user can be a member of one of two types of groups:

• The primary group, or login group - is the one that is assigned to the user's files that are created by the user. The primary group's name is usually the same as the user's name. Every user must be a member of only one primary group.
• Secondary or supplementary group - used to grant a set of users certain privileges. A user may belong to 0 or more secondary groups.

List all Groups a User is a Member of

There are several methods for determining which groups a user belongs to.

The /etc/passwd file contains the primary user's group, and the /etc/group file contains the supplementary groups, if any.

Using cat, less, or grep to list the contents of those files is one technique to find the user's groups. Another alternative is to use a command that provides information about the users and groups in the system.

Using the groups command

The groups command is the most memorable command for listing all groups in which a user is a member. The command will output a list of all groups to which the currently logged-in user belongs if it is run without an argument:

groups

The primary group is the first one.

john adm cdrom sudo dip plugdev lpadmin sambashare

Provide the username as a parameter to the groups command to retrieve a list of all groups to which a given person belongs:

groups vegastack

The first group, like before, is the primary group.

vegastack : vegastack sudo

Using the id command

The id command displays information about a user and their groups. If the username is not specified, the current user's information is displayed.

To acquire information on the user vegastack, for example, type:

id vegastack

The command displays the user ID (uid), primary group (gid), and secondary groups for the user (groups)

Output

uid=1001(vegastack) gid=1001(vegastack) groups=1001(vegastack),27(sudo)

Use the -n option to print only the names instead of the numbers. The -g option prints only the primary group, while -G prints all groups.

The following program prints the names of the groups to which the current user belongs:

id -nG

Output

john adm cdrom sudo dip plugdev lpadmin sambashare

List All Members of a Group

Use the getent group command followed by the group name to get a list of all members of a group.

For example, if you wanted to find out who was in a group called developers, you could run the following command:

getent group developers

The command will print the group and all of its members if the group exists:

Output

developers:x:126:frank,mary

If there isn't an output, the group isn't active.

List All Groups

Simply open the /etc/group file to see all the groups on the system. Each line in this file corresponds to a single group.

less /etc/group

Another approach is to use the getent command, which displays entries from databases specified in the /etc/nsswitch.conf file, such as the group database, which we may query for a list of all groups.

Type the following command to receive a list of all groups:

getent group

The output is the same as when the contents of the /etc/group file are displayed. getent will display all groups from both the /etc/group file and the LDAP database if you are using LDAP for user authentication.

You may also use awk or cut to print just the first field, which contains the group's name:

getent group | awk -F: '{ print $1}'

getent group | cut -d: -f1

FAQs to List Groups on Linux

Conclusion

You learned how to find out which groups a user belongs to in this tutorial. Any Linux distribution, including Ubuntu, CentOS, RHEL, Debian, and Linux Mint, can use the same commands.

If you have any queries, please leave a comment below and we’ll be happy to respond to them.