Question: I'm using Ubuntu 18.04. I want to add my user, "davea" to the group "www-data". I tried this

```
(venv) davea@chicommons-laboratory:/var/www/html/web$ groups
davea sudo
(venv) davea@chicommons-laboratory:/var/www/html/web$ sudo usermod -a -G www-data davea
[sudo] password for davea: 
(venv) davea@chicommons-laboratory:/var/www/html/web$ groups
davea sudo

```

but as you can see, even though the command didn't give any errors, my user is still not added to the group. What am I doing wrong?

Answer: 
You need to log off and on the `davea` user to see that `davea` is a member of `www-data` group.
Or you can use newgrp

From manpage

> 
> The newgrp command is used to change the current group ID during a login session. If the optional - flag is given, the user's environment will be reinitialized as though the user had logged in, otherwise the current environment, including current working directory, remains unchanged.
> 
> 
> 

```
newgrp - www-data 

```

I use this in Live-sessions; where you usually you can not logput for reloging.