#!/bin/sh
dev=/dev/vdb
part=1
label=mydata

msg() { echo "$@" 1>&2; }
fail() { echo "$@" 1>&2; exit 1; }

set -e

[ "$(id -u)" = "0" ] || fail "not root"
umount /mnt || :
msg "wiping $dev"
# 4 of them to wipe any old filesystem data on first part
out=$(dd if=/dev/zero of=$dev bs=1M count=4 2>&1) ||
    fail "failed wiping $dev: $out"
msg "partitioning $dev"
out=$(echo "2048," | sudo sfdisk --label=gpt --force --unit=S "$dev" 2>&1) ||
    fail "failed sfdisk $dev: $out"

if [ "$1" = "mkfs" ]; then
    msg "filesystem label $label on $dev${part}"
    out=$(mkfs.ext4 -F "${dev}${part}" -L "$label" 2>&1) ||
        fail "failed mkfs.ext4: $out"
fi

sleep 1
blkid "$dev" "${dev}${part}"