local unmount problem after starting or using NFS

Hello!

=09I am posting this since I searched about it on the internet and it see= ms like=20
there are many people having these types of problems, yet no good solutio= n=20
found.
=09I want to show you some scenarios and then pose the questions, and hop= e=20
someone can help:

=09-- Local UnMounting doesn't work --

=091. consider the following:
=09=09- the linux sistem boots
=09=09- some local filesystems are automounted under /mnt (or some othe= r=20
directory)
=09=09- the NFS service starts up
=09=09- the machine finishes loading the linux system
=09=09- now, when the user logs in, if he tries to unmount a local filesy= stem=20
(umount /mnt/drive) mounted by automount, he gets umount: /mnt/drive:=20 device busy; it seems like, although the user didn't launch any process=20 which uses /mnt/drive, the NFS service somehow locked it and it cannot be= =20
locally unmounted
=09=09- note: this scenario can be avoided by not letting automount to mo= unt local=20
partitions at system startup; the NFS service must be started before any=20 local mounting takes place; however this doesn't work in scenario 2 =092. the previous scenario problem can be obtained also like this:
=09=09- NFS Server boots, no automount takes place
=09=09- NFS Client boots (another machine)
=09=09- NFS Server locally mounts /mnt/drive; please note that in this si= tuation,=20
if we want to unmount /mnt/drive, we can do so, we don't get any errors, = as=20
long as the following step takes place
=09=09- the Client mounts Server:/mnt/drive
=09=09- the Client gets its job done, then unmounts Server:/mnt/drive =09=09- if the Server tries to unmount the local filesystem (umount /mnt= /drive),=20
he gets umount: /mnt/drive: device busy; it is the same result as in=20 scenario 1
=09I did a little research and found that these two situations can be res= ovled=20
with the following steps:
=09=09a. exportfs -u Client:/mnt/drive for each client that has access = to that=20
drive (or a exportfs -ua for all exports)
=09=09b. unmount the local partition umount /mnt/drive, which succeedes=
this=20
time
=09=09c. exportfs Client:/mnt/drive for each client that has access to = that=20
drive (or a exportfs -ra for all exports)
=09OR
=09=09a. the NFS service on Server is stopped
=09=09b. unmount the local partition umount /mnt/drive =09=09c. the NFS service on Server is started

=09Anyway, it seems like this problem is valid only for the local mounted= =20
filesystems (partitions, cdrom, etc.) which appear in the '/etc/exports'=20 config file, thus shared to the outside world. It would be great if someo= ne=20
could tell us what really goes on when NFS starts up, or when the Client=20 nfs-mounts the Server's local mounted drive. I'm kind of new to linux but=
it=20
seems like on startup all entries in /etc/exports are somehow locked...=
we=20
need gurus here :)

=09Thanks in advance for any help,
=09=09Banu Cosmin.

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