This post will guide you how to add new and existing users to primary or secondary groups in your Linux Operating systems. How do add a user to a group in Linux. How to remove a user from a group. How to create or delete a Group.
- Adding a User to a Group
- Adding a User to Multiple Groups
- Removing a User from a Group
- Creating a Group
- Deleting a Group
- Changing the Primary Group of a User
Adding a User to a Group
If you want to add an existing user to a secondary group, and you can use the usermod command with -G option.
For Example, if you want to add a user called mytest to another group(mydev), just type:
$ sudo usermod -a -G mydev mytest
You can verify if the secondary group of this user is added, type:
$ id mytest
Outputs:
devops@devops:~$ id mytest uid=1001(mytest) gid=1001(mytest) groups=1001(mytest),1002(mydev)
Adding a User to Multiple Groups
If you want to add an existing user to multiple secondary groups in your Linux, and you can use usermod command with -G option and names of group separated by common character.
For example, you want to add user mytest to multiple groups(mytest2,mytest3), type:
$ sudo usermod -a -G mytest2,mytest3 mytest
Let’s check if user “mytest” is added to multiple groups by using the following command:
$ id mytest
Outputs:
devops@devops:~$ id mytest uid=1001(mytest) gid=1001(mytest) groups=1001(mytest),1002(mydev),1003(mytest2),1004(mytest3)
Removing a User from a Group
If you want to remove a user from a group, and you can use the gpasswd command. For example, you want to remove a user called mytest from a group called mytest3. Type:
$ sudo gpasswd -d mytest mytest3
Outputs:
devops@devops:~$ sudo gpasswd -d mytest mytest3 Removing user mytest from group mytest3 devops@devops:~$ id mytest uid=1001(mytest) gid=1001(mytest) groups=1001(mytest),1002(mydev),1003(mytest2)
Creating a Group
If you want to create a new group in your current Linux system, and you can use the groupadd command with a group name(mytest4), type:
$ sudo groupadd mytest4
Deleting a Group
If you want to delete an existing group, and you can use the groupdel command with a group name, type:
$ sudo groupdel mytest4
Changing the Primary Group of a User
If you want to change a user primary group, and you can use the usermod command with -g option.
For example, you want to change the primary group from mytest to mytest4. Just issuing the following command:
$ sudo usermod -g mytest4 mytest
Outputs:
devops@devops:~$ sudo usermod -g mytest4 mytest devops@devops:~$ id mytest uid=1001(mytest) gid=1005(mytest4) groups=1005(mytest4),1002(mydev),1003(mytest2) devops@devops:~$
If you want to get more information about both useradd and usermod commands, and you can type the following man command at the shell prompt:
$ man usermod $ man useradd $ man groupadd
Conclusion
You should know that how to add a user to a secondary group or multiple groups in your CentOS or RHEL or Ubuntu Linux.