resize-helper

#!/bin/sh
# Copyright (c) Fathi Boudra <fathi.boudra@linaro.org>
# All rights reserved.
# 
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 
# THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.

# we must be root
[ $(whoami) = "root" ] || { echo "E: You must be root" && exit 1; }

# we must have few tools
SGDISK=$(which sgdisk) || { echo "E: You must have sgdisk" && exit 1; }
PARTED=$(which parted) || { echo "E: You must have parted" && exit 1; }
PARTPROBE=$(which partprobe) || { echo "E: You must have partprobe" && exit 1; }
RESIZE2FS=$(which resize2fs) || { echo "E: You must have resize2fs" && exit 1; }
BLKID=$(which blkid) || { echo "E: You must have blkid" && exit 1; }

# find root device
ROOT_DEVICE=$(findmnt / -o source -n)
# prune root device (for example UUID)
ROOT_DEVICE=$(realpath ${ROOT_DEVICE})
# get the partition number and type
ROOT_PART_NAME=$(echo "$ROOT_DEVICE" | cut -d "/" -f 3)
DEVICE_NAME=$(echo /sys/block/*/"${ROOT_PART_NAME}" | cut -d "/" -f 4)
DEVICE="/dev/${DEVICE_NAME}"
PART_ENTRY_NUMBER=$(cat "/sys/block/${DEVICE_NAME}/${ROOT_PART_NAME}/partition")
PART_TABLE_TYPE=$(${BLKID} -o value -s PTTYPE "${DEVICE}")
DEVICE_SIZE=$(cat "/sys/block/${DEVICE_NAME}/size")
END_SIZE=$((DEVICE_SIZE - 1))

# in case the root device is not on a partitioned media
if [ "x$PART_ENTRY_NUMBER" = "x" ]; then
	${RESIZE2FS} "${ROOT_DEVICE}"
	exit 0
fi

if [ "$PART_TABLE_TYPE" = "gpt" ]; then
	END_SIZE=$((DEVICE_SIZE - 34))
	${SGDISK} -e ${DEVICE}
	${PARTPROBE}
fi
${PARTED} -m ${DEVICE} u s resizepart ${PART_ENTRY_NUMBER} ${END_SIZE}
${PARTPROBE}
${RESIZE2FS} "${ROOT_DEVICE}"