How to avoid fscks caused by "device busy" at reboot time.(#28)

How to avoid fscks caused by "device busy" at reboot time.(#28)
If you often get device busy errors on shutdown that leave the filesystem in need of an fsck upon reboot, here is a simple fix:
To /etc/rc.d/init.d/halt or /etc/rc.d/rc.0, add the line

mount -o remount,ro /mount.dir

for all your mounted filesystems except /, before the call to umount -a. This means if, for some reason, shutdown fails to kill all processes and umount the disks they will still be clean on reboot. Saves a lot of time at reboot for me.