Re: WARNING: expand-on-first boot might shrink your partition on Debian bookworm

[Jan Kiszka <jan.kiszka@siemens.com>]

On 08.07.22 08:35, Schmidl, Tobias (T CED SES-DE) wrote:
> Am Donnerstag, dem 07.07.2022 um 09:48 +0200 schrieb Florian Bezdeka:
>> Hi all,
>>
>> here comes another Debian bookworm related problem. This time related to
>> expand-on-first-boot, which destroys my image during the fist boot.
>>
>> The linux-util packages has been updated and includes some changes
>> related to partition alignment. See [1]. (Thanks Henning for pointing me
>> here.) It might happen now that the last partition is shrinked instead
>> of expanded.
>>
>> […]
>>
>> Booting up again stops in the initrd with the following error:
>>
>> (initramfs) [    1.978569] EXT4-fs (sda2): bad geometry: block count
>> 550586 exceeds size of device (550400 blocks)
>>
>> resize2fs called from expand-last-partition.sh already throws a warning
>> resize2fs: New size smaller than minimum (550586)
>>
>>
> 
> 
> I might have a solution:
> 
> 
> 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 31f1ae3..5da9f7a 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 +22,23 @@ if [ "${ROOT_DEV}" = "${BOOT_DEV}" ]; then
>         exit 1
>  fi
> 
> +# this value is purely speculative
> +BUFFER_SIZE=16384
> +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
> +       PART_SIZE=$(cat "${PARTITION}"/size)
> +       ALL_PARTS_SIZE=$((ALL_PARTS_SIZE + PART_SIZE))
> +done
> +echo "Disk ${BOOT_DEV}: ${DISK_SIZE}, all partitions combined: ${ALL_PARTS_SIZE}" >&2
> +
> +MINIMAL_SIZE=$((ALL_PARTS_SIZE + BUFFER_SIZE))
> +if [ "$DISK_SIZE" -lt "$MINIMAL_SIZE" ]; then
> +       echo "Disk is not big enough, won't resize. Current size: $DISK_SIZE, minimal size for resizing: $MINIMAL_SIZE" >&2
> +       #exit 0
> +fi
> +
>  LAST_PART="$(sfdisk -d "${BOOT_DEV}" 2>/dev/null | tail -1 | cut -d ' ' -f 1)"
> 
>  # Transform the partition table as follows:
> 
> 
> The problem is - the numbers don't really add up. We see a difference of
> 128 blocks - that IMHO isn't reflected anywhere in the code.
> 
> I would even opt for bigger numbers, maybe 32k blocks. If the difference
> in size is so low, the benefit of resizing is marginal.
> 

Yeah, everything below some MB is not worth trying to change the size.
It rather usual a signal that something was forgotten, either to remove
this service from the image or resize it after creation if it is used
for a VM or an otherwise emulated storage (USB gadget).

Jan

-- 
Siemens AG, Technology
Competence Center Embedded Linux