Setup default filesystem for BIOS-x86 clients (type 0):
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Type these commands on the server:
  apt install debootstrap
  cd /var/netboot/filesystems/default-bios
  mkdir root
  cd root
  debootstrap $(lsb_release -sc) .
  echo proc /proc proc defaults 0 0 > etc/fstab
  echo sysfs /sys sysfs defaults 0 0 >> etc/fstab
  chroot .
  mount -a
  ln -sf /usr/share/zoneinfo/America/New_York /etc/localtime
  echo en_US.UTF-8 UTF-8 >> /etc/locale.gen
  echo LANG=en_US.UTF-8 >> /etc/locale.conf
  apt update
  apt install locales
  apt install keyboard-configuration pxelinux syslinux-common
  apt install --no-install-recommends linux-image-amd64 firmware-linux-free
  passwd -d root
  exit
  umount proc
  umount sys
  cp usr/lib/PXELINUX/pxelinux.0 boot/pxelinux
  cp usr/lib/syslinux/modules/bios/* boot
  cp boot/initrd.img-*-amd64 boot/initrd.img
  cp boot/vmlinuz-*-amd64 boot/vmlinuz
  cd ..

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