graceful shutdown from Virtualbox with NetBSD 5.x as a guest - with no network

[Carl Brewer <carl%bl.echidna.id.au@localhost>]

G'day,
I have a couple of NetBSD 5.2 servers running as VirtualBox guests 
(OpenIndiana host).  Every now and then (~every 2 weeks), the network 
falls over and they lose their ethernet interfaces, as does the OI 
server sometimes - the only way I've been able to get it going again is 
to remove & replace a driver on the OI server and reboot everything - 
normally this is just a minor PITA, but I am going overseas for three 
weeks and won't be able to do it while I'm gone.

So, a Q&D hack - every night, reboot everything anyway and start the VB 
guests from a script - it's ugly I know, but means at worst the servers 
are down for 24 hrs.

For this to work, I need to gracefully shut down the NetBSD guests, but 
when I run VB's acpipowerbutton from VBoxmanage it does a firm kill - it 
doesn't seem to run the shutdown scripts that normally happen when you 
shutdown a box.  Running acpipowerbutton on the Linux guests does the 
right thing, it takes them through a graceful shutdown, but not so with 
NetBSD 5.2.x, AFAIK anyway.

Can anyone here suggest (or tell me what I'm doing wrong!  And no, I'm 
not getting off the OI server, ZFS is too big a win) how best to 
gracefully shut down the NetBSD guests given that I have to assume that 
the network is not available to connect?  I can just do it from a 
cronjob on the BSD boxes, but that's even clunkier.

Thank you

Carl