How to Add a User to Multiple Groups in Linux

Adding a user to multiple groups in Linux can be done using the usermod command. Here’s a step-by-step guide:

using usermod Command to add a user to Multiple Groups

To add a user to multiple groups, use the -G option followed by a comma-separated list of the groups:

sudo usermod -G group1,group2,group3 username

Replace group1,group2,group3 with the group names and username with the actual username.

For instance, to add a user named john to groups developers, designers, and marketing:

sudo usermod -G developers,designers,marketing john

Notes: This command will result in the user being removed from all other groups except the one specified with -G.

Keep the Existing Groups when adding a user to new groups in Linux

To keep the user in their existing groups while adding new ones, use the -a (append) option with -G:

sudo usermod -aG group1,group2,group3 username

The -a option is for appending the user to the specified group(s) without removing them from other groups. The -G option specifies the group(s) you want to add the user to.

This approach adds the user to a new group while keeping their existing group memberships intact.

Verifying Group Membership in LInux

After executing the command, verify the user’s group membership with:

groups username

Important Considerations

• Root privileges are required to modify user accounts.
• Ensure the groups you are adding the user to exist in the system.

FAQ on Users, Groups, and Usermod in Linux

Users

What is a user in Linux?

A user is an entity that has permission to access and interact with the Linux operating system. Users can be people, accounts tied to physical users, or accounts that run applications.

How do I create a new user in Linux?

You can create a new user in Linux using the useradd command followed by the username. For example, sudo useradd john.

What is a superuser?

A superuser, or root user, has full access to the system and can perform any administrative task. The superuser has the highest level of access rights on the system.

Groups

What is a group in Linux?

A group is a collection of users. Groups are used to organize users and manage permissions for multiple users at once.

How do I create a new group in Linux?

To create a new group, use the groupadd command. For example, sudo groupadd developers creates a new group named developers.

What are primary and secondary groups?

A primary group is the default group associated with a user’s files and activities in the system. A secondary group is any other group a user belongs to.

Usermod Command

What is the usermod command?

The usermod command in Linux is used to modify a user’s account settings, including changing the user’s groups, login name, home directory, and other configurations.

How do I add a user to a group using usermod?

To add a user to a group, use usermod -aG groupname username. Replace groupname with the group and username with the user’s name.

Can I change a user’s primary group with usermod?

Yes, you can change a user’s primary group using usermod -g groupname username.