Re: Help: nfs not able to mount large (loopback) directory

["Dean S. Messing" <deanm@sharplabs.com>]

On Fri, 2005-06-03 at 20:19 -0700, Dean S. Messing wrote:

: > I have a large .iso image (4GB) on machine B which I have loopback
: > mounted to directory /mnt/disk.
: > When I try to nfs mount B:/mnt/disk to machine A I get a "permission
: > denied" error.
: > If I replace the 4GB image on machine B with, say, a 700MB .iso image,
: > I have no problem with the NFS mount on machine A.
: > I'm running the latest version of MandrivaLinux (2005LE == Mandrake 10.2)
: > on machine B and MandrakeLinux 10.0 on machine A so the nfs utilites
: > on machine B (the server) should be nearly current.
: > In fact:
: >
: > [root@neuron ~]# rpcinfo -p
: >    program vers proto   port
: >     100000    2   tcp    111  portmapper
: >     100000    2   udp    111  portmapper
: >     100003    2   udp   2049  nfs
: >     100003    3   udp   2049  nfs
: >     100003    4   udp   2049  nfs
: >     100003    2   tcp   2049  nfs
: >     100003    3   tcp   2049  nfs
: >     100003    4   tcp   2049  nfs
: >     100021    1   udp  34593  nlockmgr
: >     100021    3   udp  34593  nlockmgr
: >     100021    4   udp  34593  nlockmgr
: >     100021    1   tcp  33635  nlockmgr
: >     100021    3   tcp  33635  nlockmgr
: >     100021    4   tcp  33635  nlockmgr
: >     100005    1   udp    846  mountd
: >     100005    1   tcp    849  mountd
: >     100005    2   udp    846  mountd
: >     100005    2   tcp    849  mountd
: >     100005    3   udp    846  mountd
: >     100005    3   tcp    849  mountd
: >     100024    1   udp    888  status
: >     100024    1   tcp    891  status
: >
: > Is it the case that nfs (mountd?) can't handle "large" files?
: > Any help will be much appreciated.
: 
: I also have found that even small ISO images will lead to problems if
: you loopback mount them and NFS export them - EG via NFS v3.
: 
: However, if I loopback mount the ISO image, copy it to an ext3 directory
: with a tar | tar pipeline, and then NFS export that ext3 directory in
: the same way, things work fine.
: 
: I'm finding that often userspace->kernel and kernel->userspace work well
: in linux, but kernel->kernel interfaces seem to have  codepaths that
: aren't always tested that much.


According to the version numbers in the output of rpcinfo, I have nfs
v4 available on the server.  I have no idea if this makes a
difference, but serving a 700MB CD image via loopback has given me no
problems.

But for some reason I can't serve a DVD .iso image.  Of course your
solution of copying the loopback mounted directory into a real
directory is a workaround.  But what a waste of space!

It seems to me that serving a DVD .iso via NFS should be a fairly
commonly done thing.  Is anyone on this list successfully doing this?

Dean


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