2020–09–20: Downsizing the multi-boot image

If the multi-boot image doesn't fit your 8GiB uSD card, because it's a tad too big, you can downsize it a bit by using this script:

#!/bin/bash

set -e -x

mkdir -p m
L=`losetup -P --show -f multi.img`
mount -o compress-force=zstd ${L}p2 m
btrfs filesystem resize 7000M m
echo ",7000M" | sfdisk -N 2 ${L}
umount m
losetup -d "$L"

truncate -s $((128+7000))M multi.img

If something fails in the middle, you may need to recover by calling umount and losetup -d yourself. losetup -l can tell you if the image is still exported as a loop device, and which one.

The image will have the size of 7128 MiB after resize and this should fit more „8“ giga something uSD cards, as there are obviously some other giga units than gigabyte and gigibyte used by some manufacturers.