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grow-var: resolve the whole disk with lsblk -d; refuse anything else #3

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grow-var: resolve the whole disk with lsblk -d; refuse anything else #3

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1793b58
grow-var: resolve the whole disk with lsblk -d; refuse anything else
mobileoverlord Aug 26, 2026
78cf804
grow-var: read sector counts from sysfs, blockdev is not in the runtime
mobileoverlord Aug 26, 2026
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17 changes: 14 additions & 3 deletions overlays/base/usr/bin/avocado-grow-var
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Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,17 @@ if [ -n "$dm_dev" ]; then
: "${blk_dev:=$var_dev}"
fi

disk=/dev/$(lsblk -no PKNAME "$blk_dev" | head -n 1)
# -d (no dependents): without it lsblk also lists the partition's holders, and
# for a dm slave the dm child's row comes first - its PKNAME is the partition
# itself, so "disk" resolved to /dev/nvme0n1p16 and `sgdisk -e` wrote a GPT
# over the LUKS2 header (observed on a Jetson Orin Nano with encrypted /var).
disk=/dev/$(lsblk -dno PKNAME "$blk_dev")
part=$(printf '%s\n' "$blk_dev" | grep -oE '[0-9]+$')
# Never let sgdisk near anything that is not a whole disk holding a table.
if [ "$(lsblk -dno TYPE "$disk" 2>/dev/null)" != "disk" ]; then
echo "grow-var: $disk (parent of $blk_dev) is not a whole disk; refusing to touch it." >&2
exit 1
fi
ptable=$(lsblk -dno PTTYPE "$disk")
echo "grow-var: $var_dev (via $blk_dev) on $disk (partition $part, $ptable table)."

Expand Down Expand Up @@ -115,9 +124,11 @@ if [ "$blk_dev" != "$var_dev" ]; then
# resize cannot happen here. The initramfs (cryptsetup-var.sh) already
# handles LUKS resize when it detects partition_sectors > dm_sectors on
# the next boot — with the key still available at that point.
# Sizes from sysfs: blockdev(8) is not in the runtime image.
sectors() { cat "/sys/class/block/$(basename "$(readlink -f "$1")")/size"; }
data_offset=$(dmsetup table "$dm_name" | awk '{print $8}')
expected_dm=$(( $(blockdev --getsz "$blk_dev") - data_offset ))
dm_sectors=$(blockdev --getsz "$var_dev")
expected_dm=$(( $(sectors "$blk_dev") - data_offset ))
dm_sectors=$(sectors "$var_dev")
if [ "$dm_sectors" -lt "$expected_dm" ]; then
echo "grow-var: LUKS container ($dm_sectors sectors) < partition ($expected_dm sectors)."
echo "grow-var: partition extended — cryptsetup-var.sh will resize LUKS + btrfs on next boot."
Expand Down