Compare /etc/fstab with /proc/mounts and try remount if something is missing

check_mounts.sh

#!/bin/bash
# Dennis Ullrich
# Version 0.1-0 (2017-07-02)
# request@decstasy.de

if [ "$1" = "-v" ]; then
	set -x 
	shift
fi

check_mounts(){
	# Ignore following fstab entry's for comparison:
	# Commentary's	^#
	# Empty lines	^$
	#				^[[:space:]]$
	# /sys			^/sys
	# /proc			^/proc
	# Lines with usbfs, debugfs, swap or tmpfs
	
	mounts="$(awk '{print $2}' /proc/mounts)"
	rc=0
	for fstab in $(grep -iv '^#\|^$\|^[[:space:]]$\|^/sys\|^/proc\|usbfs\|debugfs\|swap\|tmpfs' /etc/fstab | awk '{print $2}'); do
		# Remove last / of path if character count is greater than 1
		[[ ${#fstab} -gt 1 ]] && fstab="${fstab%/}"
		if ! grep -qs "^${fstab}$" <<<"$mounts"; then
			>&2 echo "${fstab} is not mounted!" 
			rc=1
		fi
	done

	if [ $rc -ne 1 ]; then
		echo "All filesystems are mounted."
		return 0
	else
		return 1
	fi

}

try_remount(){
	# Save reference
	mounts="$(awk '{print $2}' /proc/mounts)"

	# Try mount -a
	echo "Trying \"mount -a\""
	mount -a
	case $? in
		0)	echo "Mount -a successful."
			;;
		1)	>&2 echo "Incorrect invocation or permissions!"
			return 1
			;;
		2)	>&2 echo "System error (out of memory, cannot fork, no more loop devices)!"
			return 1
			;;
		4)	>&2 echo "Internal mount bug!"
			return 1
			;;
		8)	>&2 echo "User interrupt!"
			return 1
			;;
		16)	>&2 echo "Problems writing or locking /etc/mtab!"
			return 1
			;;
		32)	>&2 echo "Mount failure!"
			return 1
			;;
		64)	>&2 echo "Some mount(s) succeeded!"
			;;
	esac

	# Return new filesystems and check again
	newmounts="$(diff -aB --unchanged-line-format="" <(echo "$mounts") <(awk '{print $2}' /proc/mounts))"
	if [ $? -eq 0 ]; then
		>&2 echo "No new mounts detected."
		# Return 1 as something is still wrong
		return 1
	else
		echo -e "New mounts detected:\n${newmounts}"
		echo "Checking mounts again..."
		# Return 1 if there is still a missing mount
		check_mounts && return 0 || return 1
	fi
}

check_mounts || try_remount
exit $?