Re: bind mounts, crossmnt and multi client nfsv3

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Mar 21, 2011 at 01:27:05PM +0100, Dennis Jacobfeuerborn wrote:
> On 03/21/2011 04:09 AM, NeilBrown wrote:
> >On Mon, 21 Mar 2011 03:24:50 +0100 Dennis Jacobfeuerborn
> ><d.jacobfeuerborn@conversis.de>  wrote:
> >
> >>Hi,
> >>I have a storage system that is exporting many directories to multiple
> >>clients resulting in a lot of mountpoints (156) on each client. What I'm
> >>trying to do is to create a single directory on the server and then use
> >>mount --bind to mount all the different directories (which are stored on
> >>different LVM volumes) into this single export directory and finally export
> >>this directory to the clients.
> >>Now the exports man-page mentions the crossmnt option but it also mentions
> >>that it cannot be used if I want to export the directory to multiple
> >>clients. Is there another way to accomplish something like this?
> >>
> >
> >Just export the top directory with 'crossmnt' - it should work fine.
> >
> >The 'multiple clients' thing only affects 'nohide' and I think it only
> >affected it back in 2.4 days.
> >Lots changed with 2.6, but maybe not enough of the man page changed :-(
> >
> >So try with 'crossmnt' and if it doesn't work, then come back with details.
> 
> I've tried this now but it doesn't seem to work. This is the setup so far:
> 
> ===========
> 
> On the server I've created the bind mounts like this:
> 
> /mnt/vg0/vol01/country/de/a on /exports/country/de/a type none (rw,bind)
> /mnt/vg0/vol03/country/de/b on /exports/country/de/b type none (rw,bind)
> ...
> 
> Then I put the following line in /etc/exports:
> /exports 192.168.0.0/255.255.255.0(rw,anonuid=96,anongid=96,secure,no_root_squash,wdelay,sync,crossmnt,no_subtree_check)
> 
> additionally these exports exist for each volume:
> /mnt/vg0/vol01/country 213.131.252.0/255.255.255.0(rw,anonuid=96,anongid=96,secure,no_root_squash,wdelay,sync)

I'm a bit confused by the paths and ip blocks:

	- You want to export the path that the client sees
	  (/exports/country/whatever), not the original path
	  (/mnt/vg0/...).
	- If you expect clients to be able to traverse from /exports/ to
	  filesystems underneath, then you'd want to make sure /exports/
	  is exported to anything that the filesystems underneath are.

But actually you should only need the first /exports entry; filesystems
underneath should inherit export options from the parent.

--b.

> 
> ===========
> 
> On the client I've mounted this export like this:
> mount -o
> rw,noatime,tcp,rsize=8192,hard,intr,nfsvers=3,addr=192.168.0.8
> 192.168.0.8:/exports/country/de /data/country/de
> 
> This succeeds and I can see the letters a-z in /data/country/de
> however these directories are all empty so crossing the filesystem
> border doesn't seem to work.
> 
> ===========
> 
> The server is an openfiler appliance:
> 
> [root@exonas900 ~]# conary q|grep nfs
> libnfsidmap=0.20-1.1-1
> nfs-client=1.0.10-4.6-1
> nfs-server=1.0.10-4.6-1
> nfs-utils=1.0.10-4.6-1
> [root@exonas900 ~]# uname -a
> Linux exonas900 2.6.26.8-1.0.11.smp.gcc3.4.x86.i686 #1 SMP Sat Jan
> 10 22:09:09 GMT 2009 i686 i686 i386 GNU/Linux
> 
> ===========
> 
> The client I'm testing with is a Centos 5 system:
> 
> [root@wmembf10 ~]# rpm -qa|grep nfs
> nfs-utils-lib-1.0.8-7.6.el5
> nfs-utils-1.0.9-47.el5_5
> [root@wmembf10 ~]# uname -a
> Linux wmembf10.tmm.cvsn.de 2.6.18-194.11.4.el5xen #1 SMP Tue Sep 21
> 05:40:24 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux
> 
> Regards,
>   Dennis
> --
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