mkzftree /actualroot /tmp/root.ztree
genisoimage -o /tmp/root.iso -R -iso-level=4 -hide-rr-moved -p \
	'ThinLinX Pty Ltd' -V tlxroot_r -z /tmp/root.ztree

# can obtain size of iso in 2048-byte blocks using:
od -A none -td -N 4 -j 32848 /tmp/root.iso
# or using primitive busybox version of od:
od -D /tmp/root.iso | awk '$1 == "0100120" {print $2; exit}'
or:
dd if=/tmp/root.iso bs=1 count=4 skip=32848 status=none | od -D | awk '{print $2}'

# can obtain size of fat filesystem in 512 byte blocks using:
od -A none -td -N 2 -j 19 /dev/sda1
od -A none -td -N 4 -j 32 /dev/sda1 # if above is zero
# crude busybox equivalent:
dd if=/dev/sda1 bs=1 count=2 skip=19 status=none | od -d | awk '{print $2}'
dd if=/dev/sda1 bs=1 count=4 skip=32 status=none | od -D | awk '{print $2}' # if above is empty