Linux-NFS Archive on
 help / color / Atom feed
From: Alkis Georgopoulos <>
To: "" <>
Subject: Re: bindfs over NFS shows the underlying file system
Date: Sat, 12 Oct 2019 08:03:29 +0300
Message-ID: <> (raw)
In-Reply-To: <>

Thank you very much for the feedback,

I'm testing with Ubuntu 18.04, nfs-common 1:1.3.4-2.1ubuntu5.2.
I think this means "nfs utils 1.3.4".

I tried explicitly listing all submounts in exports, and specifying an 
fsid everywhere, and that worked, for example:


...and the clients only mount /home, and then properly see the bindfs 
share permissions.

But I'd really like to avoid that as in the real scenario there are many 
submounts which are frequently added/removed, not just /home/share.

I'll try to follow your advice for debugging information.

On 10/11/19 7:47 PM, J. Bruce Fields wrote:
> On Fri, Oct 11, 2019 at 08:24:14AM +0300, Alkis Georgopoulos wrote:
>> I'm not sure if this is an NFS issue, or a bindfs issue, or if I'm
>> not using the appropriate NFS options.
>> I export my /home via NFS with:
>>      /home *(rw,async,crossmnt,no_subtree_check,no_root_squash,insecure)
>> Inside my /home I'm providing a shared folder with a bindfs mount:
>>      bindfs -u 1000 --create-for-user=1000 -g 100
>> --create-for-group=100 -p 770,af-x /home/share /home/share
>> I.e. this just sets fixed permissions for anything under /home/share.
>> And finally I mount /home on some NFS client (or on localhost):
>>      mount -t nfs server:/home /home
>> The problem is that /home/share on the client doesn't show the
>> bindfs permissions, but it shows the underlying file system of the
>> server's /home/share.
>> The crossmnt NFS option follows submounts with other file systems,
>> but not with bindfs.
>> On the other hand, if the bindfs source is on a different file
>> system than the bindfs target directory, everything works fine (i.e.
>> bindfs /other/filesystem/share /home/share).
> Huh.  I wonder if nfsd is for some reason determining the existence of a
> mountpoint by comparing some kind of filesystem id and not seeing a
> change.  Looking at the code to remind myself how this works....
> nfsd_mountpoint() is using d_mountpoint() and follow_down(), which
> should be right.  Then it's making an upcall to mountd.  That's handled
> by nfs-utils/mountd/cache.c:nfsd_export().
> The is_mountpoint() check there is indeed going to return false in your
> case because it's just comparing inode and device numbers....  But I
> think that case is only for the "mountpoint" export option.
> So I think all that matters is that export_matches() does the right
> thing, and it certainly looks like it does--it should succeed as long as
> there's a parent directory that's exported with crossmnt.
> There's some debugging you could try by looking at
> net/sunrpc/nfsd.*/content or using strace to watch rpc.mountd's reads
> and writes of net/sunrpc/nfsd.*/channel.
> What version of nfs-utils are you on?
> --b.
>> Is there any way to configure either NFS or bindfs, so that this
>> works when I only have one partition, i.e. when the share is on the
>> same file system as /home?
>> If anyone answers, please Cc me as I'm not in the list.
>> Thank you very much,
>> Alkis Georgopoulos
>> LTSP developer

      reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-11  5:24 Alkis Georgopoulos
2019-10-11 16:47 ` bfields
2019-10-12  5:03   ` Alkis Georgopoulos [this message]

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-NFS Archive on

Archives are clonable:
	git clone --mirror linux-nfs/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-nfs linux-nfs/ \
	public-inbox-index linux-nfs

Example config snippet for mirrors

Newsgroup available over NNTP:

AGPL code for this site: git clone