In the email from Monday, 11 July 2022 11:16:02 +03 user Tobias Schmidl wrote:
> If the disk is too small, resizing might have detrimental effects.
> Because of aligning issues, it could happen the the final partition is
> _smaller_ than desired, which might lead to an unusable last partition.
> 
> Signed-off-by: Tobias Schmidl <tobiasschmidl@siemens.com>
> ---
>  .../files/expand-last-partition.sh               | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git
> a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
> b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
> index c0edde7..0aa1063 100755
> ---
> a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
> +++
> b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
> @@ -22,6 +22,22 @@ if [ "${ROOT_DEV}" = "${BOOT_DEV}" ]; then
>  	exit 1
>  fi
> 
> +# this value is in blocks. Normally a block has 512 bytes.
> +BUFFER_SIZE=32768
> +BOOT_DEV_NAME=${BOOT_DEV##*/}
> +DISK_SIZE="$(cat /sys/class/block/"${BOOT_DEV_NAME}"/size)"
> +ALL_PARTS_SIZE=0
> +for PARTITION in /sys/class/block/"${BOOT_DEV_NAME}"[1-9]*; do

It seems to be working only for something like 'sda' => 'sda1'.

For RPi I have  
root@isar:~# ls /sys/class/block/ | grep mmc 
mmcblk0 
mmcblk0p1 
mmcblk0p2
So, "p" suffix is required.

Some other devices (like nvme) also need some prefix.

> +	PART_SIZE=$(cat "${PARTITION}"/size)
> +	ALL_PARTS_SIZE=$((ALL_PARTS_SIZE + PART_SIZE))
> +done
> +
> +MINIMAL_SIZE=$((ALL_PARTS_SIZE + BUFFER_SIZE))
> +if [ "$DISK_SIZE" -lt "$MINIMAL_SIZE" ]; then
> +	echo "Disk is practically already full, doing nothing." >&2
> +	exit 0
> +fi
> +
>  LAST_PART="$(sfdisk -d "${BOOT_DEV}" 2>/dev/null | tail -1 | cut -d ' ' -f
> 1)"
> 
>  # Transform the partition table as follows:


-- 
Uladzimir Bely