growroot.sh

#!/bin/sh

# Environment variables that this script relies upon:
# - root

_info() {
	echo "growroot: $*"
}

_warning() {
	echo "growroot Warning: $*" >&2
}

# This will drop us into an emergency shell
_fatal() {
	echo "growroot Fatal: $*" >&2
	exit 1
}

_growroot() {
	# Compute root-device
	if [ -z "${root##*mapper*}" ]
	then
		set -- "${root##*mapper/}"
		VOLGRP=${1%-*}
		ROOTVOL=${1#*-}
		rootdev=$(readlink -f $(pvs --noheadings | awk '/'${VOLGRP}'/{print $1}'))
		_info "'/' is hosted on an LVM2 volume: setting \$rootdev to ${rootdev}"
	else
		# Remove 'block:' prefix and find the root device
		rootdev=$(readlink -f "${root#block:}")
	fi

	# root arg was nulled at some point...
	if [ -z "${rootdev}" ] ; then
		_warning "unable to find root device"
		return
	fi

	# If the basename of the root device (ie 'xvda1', 'sda1', 'vda') exists
	# in /sys/block/ then it is a block device, not a partition
	if [ -e "/sys/block/${rootdev##*/}" ] ; then
		_info "${rootdev} is not a partition"
		return
	fi

	# Check if the root device is a partition (name ends with a digit)
	if [ "${rootdev%[0-9]}" = "${rootdev}" ] ; then
		_warning "${rootdev} is not a partition"
		return
	fi

	# Remove all numbers from the end of rootdev to get the rootdisk and
	# partition number
	rootdisk=${rootdev}
	while [ "${rootdisk%[0-9]}" != "${rootdisk}" ] ; do
		rootdisk=${rootdisk%[0-9]}
	done
	partnum=${rootdev#${rootdisk}}

	# Check if we need to strip a trailing 'p' from the rootdisk name (for
	# device names like /dev/mmcblk0p)
	tmp=${rootdisk%[0-9]p}
	if [ "${#tmp}" != "${#rootdisk}" ] ; then
		rootdisk=${rootdisk%p}
	fi

	# Do a growpart dry run and exit if it fails or doesn't have anything
	# to do
	if ! out=$(growpart --dry-run "${rootdisk}" "${partnum}") ; then
		_info "${out}"
		return
	fi

	# Wait for any of the initial udev events to finish otherwise growpart
	# might fail
	udevadm settle --timeout=30

	# Resize the root partition
	if out=$(growpart --update off "${rootdisk}" "${partnum}" 2>&1) ; then
		_info "${out}"
	else
		_warning "${out}"
		_warning "growpart failed"
	fi

	# Wait for the partition re-read events to complete so that the root
	# partition is available for mounting
	udevadm settle --timeout=30

	# Add the root partition if it didn't come back on its own
	if ! [ -e "${rootdev}" ] ; then
		partx --add --nr "${partnum}" "${rootdisk}" || \
			_warning "failed to add root device ${rootdev}"
		udevadm settle --timeout=30
	fi
}

_growroot

# vi: ts=4 noexpandtab