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

["Schmidl, Tobias" <tobiasschmidl@siemens.com>]

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.

Kind regards,

Tobias