debootstrap

Create a basic Debian system. More information: https://wiki.debian.org/Debootstrap.

Create a Debian stable release system inside the debian-root directory:

sudo debootstrap stable {{path/to/debian-root/}} http://deb.debian.org/debian

Create a minimal system including only required packages:

sudo debootstrap --variant=minbase stable {{path/to/debian-root/}}

Create an Ubuntu 20.04 system inside the focal-root directory with a local mirror:

sudo debootstrap focal {{path/to/focal-root/}} {{file:///path/to/mirror/}}

Switch to a bootstrapped system:

sudo chroot {{path/to/root}}

List available releases:

ls /usr/share/debootstrap/scripts/