Which group is user in linux

How to list all groups a user is a member of

Before delving into the 5 ways, let’s first understand some basics:

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.

It can be a difficult task if you want to assign a set of privileges to multiple users without a group. This is where the group comes in handy.

All system users are listed in the /etc/passwd file, the groups are listed in the /etc/group file, and the actual password is stored in the /etc/shadow file.

No matter what command we use, it will fetch information from these files.

There are two types of groups in Linux:

What is 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.

What is 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.

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.

Each user profile in the password file is a single line with seven fields as shown below:

$ grep "daygeek" /etc/passwd daygeek:x:1000:1000:daygeek. /home/daygeek:/bin/bash

What is /etc/group file

“/etc/group” is a text file that defines which groups a user belongs to. We can add multiple users in the same group.

Linux has three permission levels which define how users can access it. These levels are user, group and others, which controls a users access to other users’ files and folders.

/etc/group file maintains useful information about the group such as group name, group password, group ID (GIT) and membership list. Each group details is shown in a single line with four fields as shown in the ‘method #5’ listed below.

The following seven commands will help you find out which groups a user belongs to in Linux.

• groups: Show All Members of a Group.
• id: Print user and group information for the specified username.
• lid or libuser-lid: It display user’s groups or group’s users.
• getent: Get entries from Name Service Switch libraries.
• compgen: compgen is bash built-in command and it will show all available commands for the user.
• members: List members of a group.
• /etc/group file: Also, we can grep the corresponding user’s groups from the /etc/group file.

Now let’s delve into the 5 methods which can be used to find the list of groups a user is part of in Linux:

Method-1: Using groups command

The ‘groups’ command is widely used by Linux admin to list all groups a user is a member of. It prints the information of the given user’s primary and supplementary groups as shown below:

$ groups daygeek daygeek : daygeek adm cdrom sudo dip plugdev lpadmin sambashare

Run ‘groups’ command without any arguments to display the list of groups associated with the current user as shown below:

$ groups daygeek adm cdrom sudo dip plugdev lpadmin sambashare

Method-2: Using id command

The id command stands for identity. It prints real and effective user, group, and supplementary group information such as username, UID, group names and GUID as shown below:

$ id daygeek uid=1000(daygeek) gid=1000(daygeek) groups=1000(daygeek),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),118(lpadmin),128(sambashare)

Just run the ‘id’ command to view group information about the current user as shown below:

$ id uid=1000(daygeek) gid=1000(daygeek) groups=1000(daygeek),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),118(lpadmin),128(sambashare)

Method-3: Using lid command

The lid or libuser-lid command displays information about groups containing user name, which requires sudo privileges.

You should run the libuser-lid command instead of the lid on newer systems.

$ sudo libuser-lid daygeek adm(gid=4) cdrom(gid=24) sudo(gid=27) dip(gid=30) plugdev(gid=46) lpadmin(gid=116) daygeek(gid=1000) sambashare(gid=126)

Method-4: Using the getent command

The getent command displays entries from databases supported by the Name Service Switch libraries, which are configured in ‘/etc/nsswitch.conf’:

$ getent group | grep daygeek adm:x:4:syslog,daygeek cdrom:x:24:daygeek sudo:x:27:daygeek,2gadmin dip:x:30:daygeek plugdev:x:46:daygeek lpadmin:x:116:daygeek daygeek:x:1000: sambashare:x:126:daygeek

The above command shows the group name and all other members associated with that group. Use the below customized command format to print only groups for a given user:

$ getent group | grep daygeek | awk -F: '' adm cdrom sudo dip plugdev lpadmin daygeek sambashare

Run the below command to print only the primary group information of the user:

$ getent group daygeek daygeek:x:1000:

Method-5: Using the ‘/etc/group’ file

User groups information can be filtered from the ‘/etc/group’ file using grep command as shown below:

$ grep daygeek /etc/group adm:x:4:syslog,daygeek cdrom:x:24:daygeek sudo:x:27:daygeek,2gadmin dip:x:30:daygeek plugdev:x:46:daygeek lpadmin:x:116:daygeek daygeek:x:1000: sambashare:x:126:daygeek

Use the below customized command format to print only groups for a given user:

$ grep daygeek /etc/group | awk -F: '' adm cdrom sudo dip plugdev lpadmin daygeek sambashare

Bonus Tip-1: Find out all groups using compgen command

Compgen is a bash built-in command that displays all groups in the Linux system:

$ compgen -g root daemon bin sys adm . . daygeek thanu renu sudha admin u1 u2

Bonus Tip-2: Listing members of a group using member command

The member command allows you to list members of a group in Linux:

$ members sudo daygeek 2gadmin

Closing Notes

In this guide, we have shown you several commands to list all groups a user is a member of in Linux.

If you have any questions or feedback, feel free to comment below.

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How to Know The Groups of a Linux User

This quick tip teaches you how to find the groups a Linux user belongs to in Linux command line.

Groups are the essential part of basic Linux filesystem security by design. If you know about the file permissions in Linux, you already know that groups play a huge role in limiting and allowing access of files to the desired users only.

The idea is to collect users in a group based on their roles. This way, you can easily set permissions for the intended groups of user. For example, users in sudo groups can run commands with superuser privileges while other users cannot.

Now that might make you curious about knowing which groups you belong to and this is exactly what I am going to show you in this quick tutorial.

Check user group in Linux command line

To find out which groups your user account belongs to, simply use this command:

This will show all the groups you belong to.

[email protected]:~$ groups abhishek adm cdrom sudo dip plugdev lpadmin sambashare kvm

As you can see, the user abhishek belongs to groups abhishek, sudo, adm and several other groups.

I am using Ubuntu in this tutorial and Ubuntu creates a group with the same name as the user. This is why you see user abhishek belonging to group abhishek.

Find out groups of other users in Linux

You just learned to see the groups you belong to. What about checking the groups of other users on your system?

You probably already know how to list users in Linux. When you know the username, you can find which group it belongs to by using the groups command in this way:

Obviously, you’ll have to replace the user_name in the above command with the name of the other user.

[email protected]:~$ groups prakash prakash : prakash sudo

You can also check groups of more than one users at a time by

groups user_1 user_2 user_3

The output will display the groups information for each user in separate rows:

[email protected]:~$ groups abhishek prakash abhishek adm cdrom sudo dip plugdev lpadmin sambashare kvm prakash : prakash sudo

Bonus Tip: Get group information along with gid

You can also get group information of a user with id command. The additional benefit of the id command is that it also displays the uid of the user and gid of the groups. Read this article to know more about UID in Linux.

The user name is optional and by default, it will show the information about your user account.

uid=1000(abhishek) gid=1000(abhishek) groups=1000(abhishek),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),116(lpadmin),126(sambashare),127(kvm)

You can see that getting the group information of a user is a simple task. It could come in handy in many situations and I would let you experience them on your own.

Bonus Tip 2: Get primary group of a user in Linux

Every user has a default or primary group. You can check the primary group of a user with id command in the following fashion:

You can change the primary and secondary group of a user with the usermod command.

I hope this quick little tip helped you to list user groups in Linux. You may also want to read about checking the members of a group in Linux.

If you have questions or suggestions, please feel free to use the comment section.

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