Ubuntu: How to assign one or more groups to a user (via Shell/SSH)

To edit an existing user, use the usermod command on Linux.

Adding a group to a user #

The following command will help you to add a group to a user:

sudo usermod -a -G Group_Name Username

Adding multiple groups to one user at once #

If you want to add multiple groups to a user, you just need to extend the example above by multiple groups. This way you can add multiple groups to a user by using a comma separated list. Here is an example of how the whole thing is structured:

sudo usermod -a -G Group_Name,Group_Name_2,Group_Name_3 Username

Display groups of a user #

If you are not sure which groups already exist for the desired user, you can simply display them. To do this, use the command “groups”. The following example shows you how to display all groups of a user:

groups Username

List all users in Linux #

In case you do not know the username, you can simply display all users. The users and their groups are stored in the file /etc/shadow. With the help of “cat” you can easily display them, as the following example shows:

sudo cat /etc/shadow