Originally Posted by segmentation_fault
Could this work?
mount / -o remount,ro
AFAIK fsck needs the partition to be mounted read-only, not unmounted. But I don't know how the network connection is affected from this. (I have only done this localy in runlevel 1).
I doubt that this will work in normal use, you will have to do that in runlevel 1. But as the OP states that he can't reboot the machine because it is a production machine I doubt that switching to runlevel 1 is an option.