sgdisk

disk-part.sh

#!/usr/bin/env bash

set -ex

DISK=/dev/sda

SYSTEM_PART_NR=1
SYSTEM_PART_INFO=$(sgdisk $DISK -i $SYSTEM_PART_NR)
SYSTEM_PART_SIZE="10G"

SYSTEM_PART_GUID=$(sed -nr "s/^Partition unique GUID:\s+(\S+).+$/\1/p" <<< "$SYSTEM_PART_INFO")
SYSTEM_PART_FIRST_SECTOR=$(sed -nr "s/^First sector:\s+(\S+).*$/\1/p" <<< "$SYSTEM_PART_INFO")

APP_PART_NR=$((SYSTEM_PART_NR+1))

if ! $(sgdisk $DISK -i $APP_PART_NR | grep -q "does not exist"); then
    echo "Detected already existing application partition; abort repartitioning"
    exit 0
fi

SGDISK_ARGS=(
    "$DISK"
#    "--pretend"
    "--delete" "$SYSTEM_PART_NR"
    "--new" "$SYSTEM_PART_NR:$SYSTEM_PART_FIRST_SECTOR:+$SYSTEM_PART_SIZE"
    "--partition-guid" "$SYSTEM_PART_NR:$SYSTEM_PART_GUID"
    "--new" "$APP_PART_NR"
    "--partition-guid" "$APP_PART_NR:R"
    "--print"
)

sgdisk --move-second-header $DISK
sgdisk "${SGDISK_ARGS[@]}"
partprobe $DISK