2017-10-09 Interesting NFS exports problem
I am used to being unable to unmount filesystems as long as they are NFS exported. It took me a while to find out how to correctly unexport filesystems before trying to unmount them. The easy solution would be to unexport everything and just export the other filesystems, but I'd rather not interrupt NFS availability of other filesystems. So it was time to check some large filesystems again and I'd rather not do that during boot as it can delay booting for up to an hour. Currently those filesystems are exported via IPv4 and IPv6. Removing the export for IPv4 is easy:# exportfs -u 192.168.1.0/255.255.255.0:/exportBut for IPv6 it gets harder:# exportfs -u 2001:db8:a::/64:/export exportfs: Invalid unexporting option: 2001So it is still exported via IPv6. And next thing I try to unmount it and notice it's ok to unmount a filesystem that is only exported via IPv6. I guess this shows some interesting bug.