I had a similar incident (I was able to ctrl-c out of the hanging df -h though). Luckily dmesg gave me something super clear (like `nfs host <blah> unreachable`

I had a similar incident (I was able to ctrl-c out of the hanging df -h though). Luckily dmesg gave me something super clear (like `nfs host <blah> unreachable`), so I did a `umount -l` (lazy) on `/mnt/net/<blah>` and things were OK.