Comment 34 for bug 1438612

after years of suffering with this bug, I found a solution that works for me.

I put a pre-down dispatch script for network manager to dismount nfs shares when bringing the network down. This works even if a reboot is run from a shell.

In /etc/NetworkManager/dispatcher.d/nfs.sh:
/etc/NetworkManager/dispatcher.d/pre-down has a link to it as well.
#!/bin/bash

IF=$1
STATUS=$2
logger -s "********************** NetworkManager dispatch script nfs, IF="$1" STATUS="$2

case "$2" in
 pre-down)
 umount -a -t nfs
 service cups stop
 ;;

 up)
    mount -a -t nfs
 ;;

esac

I do NOT use the systemd automount fstab option as it'll try to automount when this script is trying to dismount the nfs shares.

I also have it stop cups as kubuntu sometimes hangs bringing cups down.