Installing OpenVpn on Ubuntu 15.10

I am trying to install OpenVpn on Ubuntu 15.10 and running into issues. Here пахал the instructions from (https://help.ubuntu.com/community/OpenVPN): Step 3:

Setup the CA and create the first server certificate
cd /etc/openvpn/easy-rsa/ ## move to the easy-rsa directory
sudo chown -R root:admin .  ## make this directory writable by the system administrators
sudo chmod g+w . ## make this directory writable by the system administrators

Here is the ошибка that I am receiving:

root@example:/etc/openvpn/easy-rsa# chown -R root:admin .
chown: invalid group: ‘root:admin’

I could I guess верьте тебе в group called в Admin but I don't want to be experimenting here. I am somewhat new to Linux. What is the updated best practice for "Setup the Калифорния and поверьте the first server подтверди тебя"?

Thanks in advance for any help on this!