On Wed, Mar 19, 2025 at 14:53:51 -0400, Eben King wrote:

I have this machine "alexandria". It mounts a directory from the nas
via NFS. When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything
there that should be. How do I get it to share the contents of that mount?

As I understand it, you have three machines: alexandria (a), nas (n)
and another client (c).

You have shared a directory from n, and mounted it on a (at /foo/bar).

Meanwhile, you have shared directory /foo from a, and mounted it on c.

I believe all of these shares and mounts are using NFS.

If I understand correctly, you are wondering why c cannot see the
contents of /foo/bar which is only shared between n and a.

In essence, what you are asking is "how can I re-share an NFS share
that I'm mounting as a client, to another client".

To the best of my knowledge, this is not possible.

However, what *is* possible, because I've done it, is to mount an NFS
share and then share that via Samba.

If you mount your NAS share at /foo/bar on a, and then share /foo via
Samba, which is a userspace file server, any client mounting that share
will see the contents of /foo/bar the way you expect them to.

If you need c to see the contents of n's share using NFS, then c should
mount the share directly from n, and not go through a.

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I have this machine "alexandria". It mounts a directory from the nas
via NFS. When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything
there that should be. How do I get it to share the contents of that mount?

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Great, I have that same question. Eventually came up with a workaround
that works for my case.

A while back I was trying to do exactly that, never did get it working.
My situation was:

my Truenas NAS insisted to export share path like so: /mnt/my/share

my client was hard coded to mount /home/share with zero possibility of
changing that.

so I tried to do what you are trying. A third machine mounts
/mnt/my/share then links or cross mounts to /home/share which is
exported as an NFS share.

my client machine mounts exported /home/share but it is always empty.

Eventually fixed my problem by replacing TrueNAS os with Debian on the
NAS thus gaining flexibility in share export paths. Directly exported as /home/share worked.

On 3/19/25 13:53, Eben King wrote:

I have this machine "alexandria".  It mounts a directory from the nas
via NFS.  When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything
there that should be.  How do I get it to share the contents of that
mount?

--
Thank You!

Titus Newswanger
Curtiss WI

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On Wed, Mar 19, 2025 at 02:53:51PM -0400, Eben King wrote:

I have this machine "alexandria". It mounts a directory from the nas
via NFS. When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything
there that should be. How do I get it to share the contents of that mount?

It is possible, see the file /etc/exports and its man page exports(7), specifically the options nohide and crossmnt there.

There are caveats, though (e.g. you might get duplicate inode numbers
from the two file systems), described in the above man page.

Sorry to be so handwavy, but it's a while ago I had hands-on experience
with that.

Cheers
--
t

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On 3/19/25 15:05, Greg Wooledge wrote:

On Wed, Mar 19, 2025 at 14:53:51 -0400, Eben King wrote:

I have this machine "alexandria". It mounts a directory from the nas
via NFS. When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything
there that should be. How do I get it to share the contents of that mount?

As I understand it, you have three machines: alexandria (a), nas (n)
and another client (c).

You have shared a directory from n, and mounted it on a (at /foo/bar).

Yes.

Meanwhile, you have shared directory /foo from a, and mounted it on c.

Yes.

I believe all of these shares and mounts are using NFS.

Yes.

If I understand correctly, you are wondering why c cannot see the
contents of /foo/bar which is only shared between n and a.

Correct.

In essence, what you are asking is "how can I re-share an NFS share
that I'm mounting as a client, to another client".

Correct.

To the best of my knowledge, this is not possible.

However, what *is* possible, because I've done it, is to mount an NFS
share and then share that via Samba.

I used to use SMB, but it did funny things to filenames with a colon.
These files are TV shows and movies, and colons are not infrequent. Has
it got better, or is there a config option I need to set?

If you need c to see the contents of n's share using NFS, then c should
mount the share directly from n, and not go through a.

That was my temporary workaround. I guess it'll become a permanent
workaround.

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In essence, what you are asking is "how can I re-share an NFS share
that I'm mounting as a client, to another client".
To the best of my knowledge, this is not possible.

However, what *is* possible, because I've done it, is to mount an NFS
share and then share that via Samba.

I assume it would also work if you use [unfsd](https://github.com/unfs3/unfs3). It doesn't seem to be packaged for Debian, tho.


Stefan

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On 3/19/25 16:19, tomas@tuxteam.de wrote:

On Wed, Mar 19, 2025 at 02:53:51PM -0400, Eben King wrote:

I have this machine "alexandria". It mounts a directory from the nas
via NFS. When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything
there that should be. How do I get it to share the contents of that mount?

It is possible, see the file /etc/exports and its man page exports(7), specifically the options nohide and crossmnt there.

There are caveats, though (e.g. you might get duplicate inode numbers
from the two file systems), described in the above man page.

Sorry to be so handwavy, but it's a while ago I had hands-on experience
with that.

Cheers

I've had nothing but intermittent trouble trying us use NFS like that,
so a decade or more ago, I made it a habit to create

an /sshnet directory, and then a subdir for the share by machine $name
in that, then used ssh to mount each machines /home/me dir via sshfs.
Then I wrote a bash script that when executed, mounts each machine to
its subdir so each machine is a direct path thru that subdir. I
specifically deny root thru that connection which occasionally creates problems, but I can always put a root needing file in that machine user
dir, and ssh into that machine to fix the perms and move it as needed.
sshfs Just Works   NFS found more excuses to deny that than Berny Maddof
at his best.

Everybody has his fav bag of tricks,  that's mine.

Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis

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Stefan Monnier [2025-03-19 17:34:07] wrote:

In essence, what you are asking is "how can I re-share an NFS share
that I'm mounting as a client, to another client".
To the best of my knowledge, this is not possible.

However, what *is* possible, because I've done it, is to mount an NFS
share and then share that via Samba.

I assume it would also work if you use [unfsd](https://github.com/unfs3/unfs3).
It doesn't seem to be packaged for Debian, tho.

Actually, https://tracker.debian.org/pkg/unfs3 suggests that it used to
be packaged but was removed about 15 years ago.


Stefan

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On 3/19/25 16:19, tomas@tuxteam.de wrote:

On Wed, Mar 19, 2025 at 02:53:51PM -0400, Eben King wrote:

I have this machine "alexandria". It mounts a directory from the nas
via NFS. When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything
there that should be. How do I get it to share the contents of that mount?

It is possible, see the file /etc/exports and its man page exports(7), specifically the options nohide and crossmnt there.

Great to hear. I don't suppose you know how to access /etc/exports on a
WD Mycloud Mirror? Theoretically it supports SSH but I haven't got it
to work yet.

There are caveats, though (e.g. you might get duplicate inode numbers
from the two file systems), described in the above man page.

hmm, I'll have to see if that's a problem. So the same inode number on
two different filesystems conflict? Or what do you mean?

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On Thu, Mar 20, 2025 at 01:29:39AM -0400, Eben King wrote:

On 3/19/25 16:19, tomas@tuxteam.de wrote:

On Wed, Mar 19, 2025 at 02:53:51PM -0400, Eben King wrote:

I have this machine "alexandria". It mounts a directory from the nas
via NFS. When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything there that should be. How do I get it to share the contents of that mount?

It is possible, see the file /etc/exports and its man page exports(7), specifically the options nohide and crossmnt there.

Great to hear. I don't suppose you know how to access /etc/exports on a
WD Mycloud Mirror? Theoretically it supports SSH but I haven't got it
to work yet.

I don't even know what a WD Mycloud Mirror is :)

This is the intermediate box which you'd like to re-export the mounted
file system?

There are caveats, though (e.g. you might get duplicate inode numbers
from the two file systems), described in the above man page.

hmm, I'll have to see if that's a problem. So the same inode number on
two different filesystems conflict? Or what do you mean?

The man page isn't very clear, but I guess that NFS passes the inodes
along and the client uses them for file identification (cache, what
have you) and gets confused when the server's and the server's server
inodes collide. But that's only a guess.

Cheers
--
t

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On Thu, Mar 20, 2025 at 02:04:45PM +0800, An Liu wrote:

AFAIK,

Exporting a nfs mounted location is possible via nfs-ganesha

I have no experience with this one. Thanks for reminding me :-)

Cheers
--
t

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Eben King <eben@gmx.us> writes:

I have this machine "alexandria". It mounts a directory from the nas
via NFS. When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything
there that should be. How do I get it to share the contents of that mount?

Use sshfs to mount from alexandria since you can already ssh into it?

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Eben King <eben@gmx.us> wrote:

On 3/19/25 15:05, Greg Wooledge wrote:

On Wed, Mar 19, 2025 at 14:53:51 -0400, Eben King wrote:

I have this machine "alexandria". It mounts a directory from the
nas via NFS. When I export a parent directory on alexandria, the
mount point appears empty, even though you can ssh to it and see
everything there that should be. How do I get it to share the
contents of that mount?

As I understand it, you have three machines: alexandria (a), nas (n)
and another client (c).

You have shared a directory from n, and mounted it on a
(at /foo/bar).

Yes.

Meanwhile, you have shared directory /foo from a, and mounted it on
c.

Yes.

I believe all of these shares and mounts are using NFS.

Yes.

If I understand correctly, you are wondering why c cannot see the
contents of /foo/bar which is only shared between n and a.

Correct.

In essence, what you are asking is "how can I re-share an NFS share
that I'm mounting as a client, to another client".

Correct.

To the best of my knowledge, this is not possible.

However, what *is* possible, because I've done it, is to mount an
NFS share and then share that via Samba.

I used to use SMB, but it did funny things to filenames with a colon.
These files are TV shows and movies, and colons are not infrequent.
Has it got better, or is there a config option I need to set?

If you need c to see the contents of n's share using NFS, then c
should mount the share directly from n, and not go through a.

That was my temporary workaround. I guess it'll become a permanent workaround.

It's not a workaround. It's expected behaviour. You told the NAS to
share some of its contents with alexandria. That's what it's doing. Why
would you expect it to respond to a random request from some other
computer? Alternatively, why would you expect alexandria to share
content that doesn't belong to it?

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debian-user@howorth.org.uk (HE12025-03-20):

It's not a workaround. It's expected behaviour. You told the NAS to
share some of its contents with alexandria. That's what it's doing. Why
would you expect it to respond to a random request from some other
computer?

That is not what it is doing. nas would only be replying to alexandria.
The only difference is that alexandria is asking on behalf of client and
not on its own behalf.

Alternatively, why would you expect alexandria to share
content that doesn't belong to it?

There are many scenarios where it is useful, you just have to exercise
your imagination.

Maybe client does not and should not have network access to nas.

Maybe alexandria does not have the hardware to plug the disks.

Maybe alexandria implements caching that nas is not capable of doing.

And so on and so on.

Regards,

--
Nicolas George

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On Thu, Mar 20, 2025 at 01:32:27PM +0100, Nicolas George wrote:

debian-user@howorth.org.uk (HE12025-03-20):

It's not a workaround. It's expected behaviour. You told the NAS to
share some of its contents with alexandria. That's what it's doing. Why would you expect it to respond to a random request from some other computer?

That is not what it is doing. nas would only be replying to alexandria.
The only difference is that alexandria is asking on behalf of client and
not on its own behalf.

Alternatively, why would you expect alexandria to share
content that doesn't belong to it?

There are many scenarios where it is useful, you just have to exercise
your imagination.

Agreed.

Besides, we already know NFS can do that (with caveats). I wonder
whether people read the other postings in the threads they reply
to :)

And, as someone pointed out, ganesha NFS (a user-space server)
seems to explicitly allow that. Available as a Debian package
(of course, the NAS will be running something and not letting
the user change it, violating lots of free software licenses
in the process, but people keep paying for that, so...)

Cheers
--
t

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Exporting a nfs mounted location is possible via nfs-ganesha

Oh nice! Looks like this is a similar tool to unfs3, just more recent
and still actively developed.
Thanks,


Stefan

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On 3/20/25 01:43, tomas@tuxteam.de wrote:

On Thu, Mar 20, 2025 at 01:29:39AM -0400, Eben King wrote:

On 3/19/25 16:19, tomas@tuxteam.de wrote:

On Wed, Mar 19, 2025 at 02:53:51PM -0400, Eben King wrote:

I have this machine "alexandria". It mounts a directory from the nas
via NFS. When I export a parent directory on alexandria, the mount
point appears empty, even though you can ssh to it and see everything
there that should be. How do I get it to share the contents of that mount?

It is possible, see the file /etc/exports and its man page exports(7),
specifically the options nohide and crossmnt there.

Great to hear. I don't suppose you know how to access /etc/exports on a
WD Mycloud Mirror? Theoretically it supports SSH but I haven't got it
to work yet.

I don't even know what a WD Mycloud Mirror is :)

A two-disk NAS. Probably a pretty old one as it's been EOLed by the manufacturer. But hey, it works for me.

This is the intermediate box which you'd like to re-export the mounted
file system?

Right. NAS:/nfs/Movies is mounted on alexandria by NFS as
/files/movies. Alex exports /files by NFS. My computer mounts alexandria:/files and sees /files/movies/ as empty.

There are caveats, though (e.g. you might get duplicate inode numbers
from the two file systems), described in the above man page.

hmm, I'll have to see if that's a problem. So the same inode number on
two different filesystems conflict? Or what do you mean?

The man page isn't very clear, but I guess that NFS passes the inodes
along and the client uses them for file identification (cache, what
have you) and gets confused when the server's and the server's server
inodes collide. But that's only a guess.

OK, thanks.

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<tomas@tuxteam.de> wrote:

On Thu, Mar 20, 2025 at 01:32:27PM +0100, Nicolas George wrote:

debian-user@howorth.org.uk (HE12025-03-20):

It's not a workaround. It's expected behaviour. You told the NAS
to share some of its contents with alexandria. That's what it's
doing. Why would you expect it to respond to a random request
from some other computer?

That is not what it is doing. nas would only be replying to
alexandria. The only difference is that alexandria is asking on
behalf of client and not on its own behalf.

Alternatively, why would you expect alexandria to share
content that doesn't belong to it?

There are many scenarios where it is useful, you just have to
exercise your imagination.

Agreed.

Besides, we already know NFS can do that (with caveats). I wonder
whether people read the other postings in the threads they reply
to :)

I certainly don't always read all the posts in a long thread before
replying. And I stand by what I wrote, although I'd now qualify it by
saying that that's the default position and it can now be overridden.

And I try not to respond with rude responses, although sometimes it is difficult.

And, as someone pointed out, ganesha NFS (a user-space server)
seems to explicitly allow that. Available as a Debian package
(of course, the NAS will be running something and not letting
the user change it, violating lots of free software licenses
in the process, but people keep paying for that, so...)

Cheers

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On Thu, Mar 20, 2025 at 05:59:34PM +0000, debian-user@howorth.org.uk wrote:

<tomas@tuxteam.de> wrote:

[...]

Besides, we already know NFS can do that (with caveats). I wonder
whether people read the other postings in the threads they reply
to :)

I certainly don't always read all the posts in a long thread before
replying. And I stand by what I wrote, although I'd now qualify it by
saying that that's the default position and it can now be overridden.

And I try not to respond with rude responses, although sometimes it is difficult.

Sorry if that came across as rude. It was meant tongue-in-cheek,
especially because I'm aware I fail in the same way more than
once.

Apologies.

Cheers
--
t

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On Thu, Mar 20, 2025 at 08:09:48PM +0100, Nicolas George wrote:

tomas@tuxteam.de (HE12025-03-20):

Sorry if that came across as rude.

Do not be: not reading before replying at least to see if what one is
about to reply has already been addressed and therefore wasting
everybody's time is way ruder than your message might seem.

But I genuinely am. It wasn't intended. As I wrote, I do fall into the
same trap more often than I'd like to admit.

Cheers
--
t

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tomas@tuxteam.de (HE12025-03-20):

Sorry if that came across as rude.

Do not be: not reading before replying at least to see if what one is
about to reply has already been addressed and therefore wasting
everybody's time is way ruder than your message might seem.

Regards,

--
Nicolas George

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On 3/20/25 13:36, 🦓 wrote:

Eben King <eben@gmx.us>:

NAS:/nfs/Movies is mounted on alexandria by NFS as /files/movies. Alex
exports /files by NFS. My computer mounts alexandria:/files and sees
/files/movies/ as empty.

Why don't you
mount alexandria:/files /files &&
mount nas:/nfs/Movies /files/movies
rather than -o nohide,crossmnt?

Here is just a test environment for the share's real use, on the TV box.
It's a cheap box, but it runs Kodi, so that's something. I figure if
I do nothing special here and it works, it'll probably work there.

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