2007-11-10 21:36:45

by Roland

[permalink] [raw]
Subject: nfs exports & bind mounts

Hi !

i think everybody knows bind mounts.

i can do:

touch /otherpath/dummyfile
mount -bind /path/file /otherpath/dummyfile

so /path/file becomes accessible via /otherpath/dummyfile - dummyfile has the same size as file after successful bind-mount

i can loopback-mount /otherpath/dummyfile to /otherpath/mnt if file/dummyfile contains a filesystem

when i export /otherpath via nfs (crossmnt), from the client side i can access the contents of the filesystem inside file/dummyfile via /otherpath/mnt - but i cannot access the contents of dummyfile itself, i.e. the bind-mount seems to get lost on export.

can someone tell if this is expected behaviour or if this is a bug ?

regards
roland
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2007-11-10 22:26:21

by Trond Myklebust

[permalink] [raw]
Subject: Re: nfs exports & bind mounts


On Sat, 2007-11-10 at 22:36 +0100, [email protected] wrote:
> Hi !
>
> i think everybody knows bind mounts.
>
> i can do:
>
> touch /otherpath/dummyfile
> mount -bind /path/file /otherpath/dummyfile
>
> so /path/file becomes accessible via /otherpath/dummyfile - dummyfile has the same size as file after successful bind-mount
>
> i can loopback-mount /otherpath/dummyfile to /otherpath/mnt if file/dummyfile contains a filesystem
>
> when i export /otherpath via nfs (crossmnt), from the client side i can access the contents of the filesystem inside file/dummyfile via /otherpath/mnt - but i cannot access the contents of dummyfile itself, i.e. the bind-mount seems to get lost on export.
>
> can someone tell if this is expected behaviour or if this is a bug ?

The NFS client will not cross a mount point unless the target is a
directory. That is not a bug, it is expected behaviour.

Trond


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2007-11-10 22:39:54

by Roland

[permalink] [raw]
Subject: Re: nfs exports & bind mounts

ok, that explains why bind-mounting and exporting directories works, but no=
t files.

thanks!
=

> -----Urspr=FCngliche Nachricht-----
> Von: Trond Myklebust <[email protected]>
> Gesendet: 10.11.07 23:26:35
> An: [email protected]
> CC: [email protected]
> Betreff: Re: [NFS] nfs exports & bind mounts


> =

> =

> On Sat, 2007-11-10 at 22:36 +0100, [email protected] wrote:
> > Hi !
> > =

> > i think everybody knows bind mounts.
> > =

> > i can do:
> > =

> > touch /otherpath/dummyfile
> > mount -bind /path/file /otherpath/dummyfile
> > =

> > so /path/file becomes accessible via /otherpath/dummyfile - dummyfile h=
as the same size as file after successful bind-mount
> > =

> > i can loopback-mount /otherpath/dummyfile to /otherpath/mnt if file/dum=
myfile contains a filesystem
> > =

> > when i export /otherpath via nfs (crossmnt), from the client side i can=
access the contents of the filesystem inside file/dummyfile via /otherpath=
/mnt - but i cannot access the contents of dummyfile itself, i.e. the bind=
-mount seems to get lost on export.
> > =

> > can someone tell if this is expected behaviour or if this is a bug ?
> =

> The NFS client will not cross a mount point unless the target is a
> directory. That is not a bug, it is expected behaviour.
> =

> Trond
> =

> =



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