Setting up Raspbian rootfs on Ubuntu

init_rootfs.sh

#!/bin/bash

# For Ubuntu.  Probably works elsewhere too.
# This script downloads the Raspbian file system into ~/rpi/chroot-raspbian-armhf
# It also chroots you into the directory, so you can act as a Raspbian user.
# This was all taken from here: http://superpiadventures.com/2012/07/development-environment/

mkdir -p ~/rpi
cd ~/rpi

# Get some packages.
sudo apt-get install qemu-user-static debootstrap

# This step takes a little while.  Don't do it on a low battery.
sudo qemu-debootstrap --arch armhf stretch chroot-raspbian-armhf http://archive.raspbian.org/raspbian

# Mount some filesystems.  These calls to "mount" need to be done
# again after rebooting, so consider making a BASH alias.
#sudo mount -t proc proc ~/rpi/chroot-raspbian-armhf/proc
#sudo mount -t sysfs sysfs ~/rpi/chroot-raspbian-armhf/sys
#sudo mount -o bind /dev ~/rpi/chroot-raspbian-armhf/dev

# chroot into the Raspbian filesystem
# Do this each time you need to work with the Raspbian files.
# Again, consider making a BASH alias.
#sudo LC_ALL=C chroot ~/rpi/chroot-raspbian-armhf

# Add the Raspbian repo and set up a GPG key.
echo "deb http://archive.raspbian.org/raspbian stretch main" >> /etc/apt/sources.list
wget http://archive.raspbian.org/raspbian.public.key -O - | apt-key add -
apt-get update

stretch-armhf

[stretch-armhf]
description=Raspbian 64-bit chroot based on Stretch
type=directory
directory=/home/pi/rpi/chroot-raspbian-armhf
users=pi
groups=pi
root-users=pi
setup.copyfiles=default/copyfiles
setup.fstab=default/stretch-armhf.fstab
#/etc/schroot/chroot.d/

stretch-armhf.fstab

# fstab: static file system information for chroots.
# Note that the mount point will be prefixed by the chroot path
# (CHROOT_PATH)
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
/home/pi/rpi/chroot-raspbian-armhf/bin                /bin        none    rw,bind         0       0
/proc           /proc           none    rw,bind         0       0
/sys            /sys            none    rw,bind         0       0
/dev            /dev            none    rw,bind         0       0
/dev/pts        /dev/pts        none    rw,bind         0       0
/home           /home           none    rw,bind         0       0
/tmp            /tmp            none    rw,bind         0       0

# It may be desirable to have access to /run, especially if you wish
# to run additional services in the chroot.  However, note that this
# may potentially cause undesirable behaviour on upgrades, such as
# killing services on the host.
/run           /run            none    rw,bind         0       0
/run/lock      /run/lock       none    rw,bind         0       0
/dev/shm       /dev/shm        none    rw,bind         0       0
/run/shm       /run/shm        none    rw,bind         0       0