Add an Existing User Account to a Group
To add an existing user account to a group on your system, use the usermod command, replacing examplegroup with the name of the group you want to add the user to andexampleusername with the name of the user you want to add.
usermod -a -G examplegroup exampleusername
Change a User’s Primary Group
While a user account can be part of multiple groups, one of the groups is always the “primary group” and the others are “secondary groups”. The user’s login process and files and folders the user creates will be assigned to the primary group.
To change the primary group a user is assigned to, run the usermod command, replacingexamplegroup with the name of the group you want to be the primary and exampleusernamewith the name of the user account.
usermod -g groupname username
View the Groups a User Account is Assigned To
To view the groups the current user account is assigned to, run the groups command. You’ll see a list of groups.
groups exampleusername
Add a User to Multiple Groups
While assigning the secondary groups to a user account, you can easily assign multiple groups at once by separating the list with a comma.
usermod -a -G group1,group2,group3 exampleusername
View All Groups on the System
If you want to view a list of all groups on your system, you can use the getent command:
getent group
