If I need to reinstall a Ubuntu/Debian-based Linux OS (or mirror a software selection to another machine), this is how it can be done. On the source machine:
su
dpkg --get-selections > ~/Package.list
cp -R /etc/apt/sources.list* ~/
apt-key exportall > ~/repository.keys
Then just copy the files to the target machine:
I have not been keeping log files for my web server until the beginning of 2016, when I needed to trace access to certain files (I started to use awstats, mostly because I was familiar with it since I had used it years ago when my site was still running on a Red Hat server). In March 2016 I luckily started to use Let's Encrypt. I had used another "free" service before, which got recently into big trouble as they apparently had not control over their own security.
OpenVPN
sudo systemctl start openvpn@client
The "client" is derived from the configuration file name (/etc/openvpn/client.conf). If your configuration file is server.conf, the command needs to be
sudo systemctl start openvpn@server
When you want the service to start up automatically during system boot, you issue:
sudo systemctl enable openvpn@server
Templated versus non-templated services