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: 
your command is good.
you can check the group with 

```
getent group | grep davea

```

if your user are in group www-data, you just have to relog your user davea.

regards
You need to log off and on the `davea` user to see that `davea` is a member of `www-data` group.