[PATCH] expand-on-first-boot: Check size before resizing

[PATCH] expand-on-first-boot: Check size before resizing

[Tobias Schmidl]

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              | 17 +++++++++++++++++
 1 file changed, 17 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..3b944be 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 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
+	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:
-- 
2.36.1

Re: [PATCH] expand-on-first-boot: Check size before resizing

[Henning Schild]

Am Fri, 8 Jul 2022 13:15:21 +0200
schrieb Tobias Schmidl <tobiasschmidl@siemens.com>:

> 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              | 17
> +++++++++++++++++ 1 file changed, 17 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..3b944be 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 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
> +	PART_SIZE=$(cat "${PARTITION}"/size)
> +	ALL_PARTS_SIZE=$((ALL_PARTS_SIZE + PART_SIZE))
> +done
> +echo "Disk ${BOOT_DEV}: ${DISK_SIZE}, all partitions combined:

This is too verbose, one echo before we step out is enough.

> ${ALL_PARTS_SIZE}" >&2 +
> +MINIMAL_SIZE=$((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

"Disk is practically already full, doing nothing."

All the numbers are maybe for someone who runs bash -x ... which they
can always do. All that runs in a context where human readable output
is not useful, just a summary message on how it all ended ...

> +	exit 0
> +fi
> +
>  LAST_PART="$(sfdisk -d "${BOOT_DEV}" 2>/dev/null | tail -1 | cut -d
> ' ' -f 1)" 
>  # Transform the partition table as follows: