My desktop is running Chimaera, and I saw this with Beowulf, but didn't
spend much time on it then.

My network connection is via WiFi, and I have permanent NFS mounts in
place. I run SysV init.

During halt or shutdown via init scripts, NetworkManager is terminated
before the NFS unmount, which brings down the active NIC, and usually
the unmount hangs forever, so I have to do a hard reset or power-off.

After futzing with it for a while, trying to find a more elegant
solution, I ended up just renaming K01network-manager and K02sendsigs in
rc0.d and rc6.d. Now shutdown and reboot run reliably.

Before that, I tried renaming K01network-manager to K06network-manager,
to place it after the NFS unmount, but it ran earlier anyway.

I also tried shielding NetworkManager from sendsigs, and I think it
would have worked if I could make K0.network-manager run later, but that
was about the point I gave up and took a virtual hammer to the issue.