I have two AIX boxes, A1 and A2, both with 5.1. On A1, the directory
'/backups' is exported to A2, where it is mounted on '/daily'. A1 has gone
down in flames, while processes on A2 were accessing '/daily'.

Trying to unmount it, I get:

umount: 1831-015 16 error while unmounting A1:/backups -
The requested resource is busy.

'fuser /daily' just hangs there forever...
'lsof /daily':

lsof: WARNING: can't stat() unknown file system /daily
Output information may be incomplete.
assuming "dev=0x8000000d" from mount table

reports no processes, but with the above warning. BTW, I used 'umount -f'
with similar outcome.
Furthermore, commands like 'ls /' hang as well.
I have tried stopping NFS followed by changing the entry in /etc/filesytems,
then starting NFS, to no avail.
Is there anything that can be done short of rebooting A2?
Thanks!
-Bela
--
"... I shook my family tree, and a bunch of NUTS fell out ..."

You pointed if fact 2 differents things.

1) A1 is "off", then you cannot umount it.
Just create temporarily an alias to A2 in your
file /etc/hosts of A2 ... then you will be able
to umount it, as "A1" will be accessible to say
that /backups is not more avalaible.

2) ls / does not work
This is just because you cannot find access
information about /daily (e.g. ls /usr works).

Do not worry, umount /daily and all will be ok.

Kind regards,
Stephane