System hang on shutdown when running freebsd-update

[Juan Ramón Molina Menor]

> Another update. I narrowed down the issue due to /sbin/init being replaced. This might be the magic that freebsd-update does to make the crash happen. (Although there might be more situations that cause a hang.)
>
> I can completely reliably trigger the hang on a default 10.1-RELEASE install on UFS2 in VMware Fusion with the following procedure:
>
> # chflags noschg /sbin/init
> # cp -Rp /sbin/init /sbin/init2
> # rm -f /sbin/init
> # mv /sbin/init2 /sbin/init
> # chflags schg /sbin/init
> # reboot
> => Hang after "All buffers synced."
These commands do not trigger the issue here on a 10.1-RELEASE on VMware 
Player, but do it in a real system with the same release, both i386. 
When I last freebsd-updated this latter machine from 10.0 to 
10.1-RELEASE, I also remember seeing the hang on shutdown.

Hope it helps,
Juan