Debian 10 (Buster) for arm64

Install:

sudo apt-get install qemu qemu-user-static debootstrap kpartx

Create a new space image:

sudo dd if=/dev/zero of=rootfs.img  bs=1048576 count=1900

Make a loop device with losetup

sudo losetup -f --show rootfs.img

ex: /dev/loop19  <- pre="" success="">

Partition:

1.sudo fdisk /dev/loop19
2.sudo losetup -d /dev/loop0

Format & mount:

1. sudo kpartx -va rootfs.img
1. sudo mkfs.ext4 /dev/mapper/loop19p1
2. sudo mount /dev/mapper/loop19p1 /mnt

Download:

1. mkdir -p /mnt/usr/bin
2. cp /usr/bin/qemu-aarch64-static /mnt/usr/bin/

               (for arm 64 bit)

3. sudo debootstrap --arch arm64 buster /mnt https://deb.debian.org/debian/

Set up dns

sudo cp /etc/resolv.conf /mnt/etc/

Change root

sudo mount -t proc /proc /mnt/proc
sudo mount -t sysfs /sys /mnt/sys
sudo mount -o bind /dev /mnt/dev
sudo mount -o bind /dev/pts /mnt/dev/pts

sudo chroot /mnt
or 
sudo chroot /mnt /bin/bash

follow this page to install the required packages

umount /mnt

sudo umount /mnt/dev/pts
sudo umount /mnt/dev
sudo umount /mnt/sys
sudo umount /mnt/proc

ref:
1. [心] 誌
2. Quick and easy bootstrap of Debian 8 (Jessie) for armhf