Control NFS exported filesystems

[Mark R. Ludwig]

In article <8567 at awdprime.UUCP>, marc at ekhomeni (Marc Wiz) writes:
>In article <91169.000329CALT at SLACVM.SLAC.STANFORD.EDU>,
>CALT at SLACVM.SLAC.STANFORD.EDU writes:
>> By exprience, I learned that mounting NFS filesystems by the
>> hard/foreground options may cause the machines hanging, while
>> by the soft/backgroud options seems to work OK.
>>
>
>To put it mildly this is not a good thing to do.  Remember if you mount the
>filesystem soft the client process will get an error after three
>retries.  If your
>application can handle this fine but I have to wonder how many applications
>can not.  If you care about your data I recommend hard mounts.  At least when
>the server/network comes back up the data will be written/read to/from
>the server.

I agree fully.  At least one of the Sun administration manuals states
it bluntly: if you are mounting the NFS read/write, you should mount
it hard.  To do otherwise is to risk corrupted files.  However, I
believe if you have *very* intelligent applications manipulating the
files, you may disregard this warning, but I dare say the average Unix
utility is not in this category.  Furthermore, why would you want
this?  Since your application probably really wants to write the file
it was trying to write when the server went silent, then your
application has to keep trying until the server responds.  With
``hard'' the system does it for you.

The second part which I want to address is the foreground/background
part.  We use the ``bg'' option routinely, because the NFS partitions
are not required for the system to operate, and this allows the system
to finish multi-user startup without mounting all the NFS partitions.
The NFS partitions are only required for certain applications to run.
If the partition is required for the system, you probably must use
foreground.

>> Here comes a problem: If some machine DOES mount my exported filesystems
>> by the hard/foreground optins, it may cause my machines hanging. Is there
>> any way to configure my exporting filesystems as follows:
>>    Only the machines which use the soft/backgronud options will be allowed
>> to use my exported filesystems.

Come again?  You're saying that the *server* is hanging because the
*client* mounts the NFS hard?  I've never seen that happen.

>What are you trying to accomplish?

Right.  This is the first question we have to ask.  It helps to get
answers when you explain what you really want to do, and the
circumstances which caused you to be wedged into the corner.  Maybe
then we can get you centered in the room.$$
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