In computer networking, TUN and TAP are virtual network kernel devices. Being network devices supported entirely by software, they differ from ordinary network devices which are backed up by hardware like network adapters. This is required to set up a VPN on your VPS package.
You can enable TUN/TAP through your Servers panel, just by clicking on "Enable TUN/TAP adapter" as shown below:
Make sure to wait for up to 5 minutes, until the change is fully applied.
You can test if it was enabled correctly by connecting to your virtual machine and executing the following:
The output should be:
cat: /dev/net/tun: File descriptor in bad state