Run Ubuntu Installer from any GRUB-based system

So if I have a KVM VPS and the VPS provider doesn't provide Ubuntu 16.04 images nor mounting ISO images…

1. Get ISO from http://cdimage.ubuntu.com/netboot/.

   wget -O/tmp/mini.iso http://mirrors.zju.edu.cn/ubuntu/dists/xenial/main/installer-amd64/current/images/netboot/mini.iso

2. Unpack the ISO to /livecd.

   apt install p7zip-full
   mkdir /livecd
   cd /livecd
   7z x /tmp/mini.iso

3. Reboot and spam ↑/↓ or hold Ctrl to enter GRUB menu
4. Press C to enter GRUB console
5. Enter one of the following code snippets into the console

xenial-netboot-install.cfg

linux	/livecd/linux --- quiet
initrd	/livecd/initrd.gz

xenial-netboot-expert-install.cfg

linux	/livecd/linux priority=low ---
initrd	/livecd/initrd.gz

xenial-netboot-rescue.cfg

linux	/livecd/linux rescue/enable=true --- quiet
initrd	/livecd/initrd.gz