Below I give some simple command to run a ubuntu:16.04 lxd container. LXD container is fast, very efficient, very low-footprint virtual machine. I recommend people who didn't need low-level system control (such as disk, loopback device) give it a try. I think this kind of lightweight virtual machine would benefit people who study machine learning or similar scientific computing.
Varies images is provided by Canonical in http://images.linuxcontainers.org/
Note that lxd has some limitaions. Such as you can't
- setup loopback device
- mount fuse file system
- have bridged network.
- load/remove kernel module ... (But if you choose to run a priviledged lxd virtual machine, some limitations might not exist anymore. But I haven't dig into it currently.)