Re: [NFS] export dir thru 2 diff path names

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

On Mon, Nov 10, 2008 at 11:28:04AM -0800, Murata, Dennis wrote:
> That really is the 64K question.  During my initial testing, I exported
> the parent directory.  Now I am explicitly exporting the installation
> directories, where I see the exportfs message.  In the messages log file
> on the server the mount request from the client is always the actual
> directory.

I don't see how this would be "unsafe"--if it works, go for it.

One potential trap: it's using the same client list and export options
for both, so if you think you can make one of them read-only and one of
them writeable, for example, you'll be disapointed.

--b.

> 
> Wayne 
> 
> > -----Original Message-----
> > From: Sev Binello [mailto:sev-IGkKxAqZmp0@public.gmane.org] 
> > Sent: Monday, November 10, 2008 1:04 PM
> > To: Murata, Dennis
> > Cc: J. Bruce Fields; nfs@lists.sourceforge.net
> > Subject: Re: [NFS] export dir thru 2 diff path names
> > 
> > Hi -
> >     Yeah, I see.
> >     So it actually looks like you can do this.
> >     I'm not 100% sure if safe --though it looks it -- so I'll 
> > probably not use it for this application.
> > 
> > Thanks
> > -Sev
> > 
> > Murata, Dennis wrote:
> > > That is correct, exportfs only shows the actual directory.  
> > The client 
> > > seems to be able to mount the directory with either.
> > >
> > > Wayne
> > >
> > >   
> > >> -----Original Message-----
> > >> From: Sev Binello [mailto:sev-IGkKxAqZmp0@public.gmane.org]
> > >> Sent: Monday, November 10, 2008 12:51 PM
> > >> To: Murata, Dennis
> > >> Cc: J. Bruce Fields; nfs@lists.sourceforge.net
> > >> Subject: Re: [NFS] export dir thru 2 diff path names
> > >>
> > >> Murata, Dennis wrote:
> > >>     
> > >>> I just tested this on a SL4.7 (RHEL 4.7 variant) using a
> > >>>       
> > >> RHEL 4.4 nfs
> > >>     
> > >>> server.  I did get the messages from exportfs about
> > >>>       
> > >> duplicate export
> > >>     
> > >>> entries.  On the client I was able to mount both the
> > >>>       
> > >> symlink and the
> > >>     
> > >>> actual directory.  They look like separate mounts.  There are two 
> > >>> entries in /proc/mounts and in /etc/mtab, one with the actual 
> > >>> directory path, one with the symlink path.  I am using
> > >>>       
> > >> autofs to mount
> > >>     
> > >>> the directories, not hardcoded.  Are you using newer 
> > distributions?
> > >>>   
> > >>>       
> > >> I tested on RHEL 4.6.
> > >> Interesting that you can still mount either one.
> > >> On the server an exportfs only shows the real path as exported.
> > >>
> > >>     
> > >>> What problems will I cause by doing this?  I am using the
> > >>>       
> > >> symlink path
> > >>     
> > >>> as the installation path for an application.  The idea is a newer 
> > >>> version can be installed into a different directory, then after 
> > >>> testing the symlink will be changed to the new 
> > installation.  Other 
> > >>> applications that reference the application will always use the 
> > >>> symlink path, as well as any user scripts.
> > >>>
> > >>> Wayne
> > >>>
> > >>>   
> > >>>       
> > >>>> -----Original Message-----
> > >>>> From: linux-nfs-owner@vger.kernel.org 
> > >>>> [mailto:linux-nfs-owner@vger.kernel.org] On Behalf Of Sev Binello
> > >>>> Sent: Monday, November 10, 2008 11:06 AM
> > >>>> To: J. Bruce Fields; nfs@lists.sourceforge.net
> > >>>> Subject: Re: [NFS] export dir thru 2 diff path names
> > >>>>
> > >>>> J. Bruce Fields wrote:
> > >>>>     
> > >>>>         
> > >>>>> On Mon, Nov 10, 2008 at 10:55:48AM -0500, Sev Binello wrote:
> > >>>>>   
> > >>>>>       
> > >>>>>           
> > >>>>>> Well the simplest approach doesn't work.
> > >>>>>> i.e put symb link and actual path in the export file & try
> > >>>>>>         
> > >>>>>>             
> > >>>> exporting
> > >>>>     
> > >>>>         
> > >>>>>> it Exportfs dereferences the link and states that
> > >>>>>>         
> > >>>>>>             
> > >>>> duplicates are not allowed.
> > >>>>     
> > >>>>         
> > >>>>>>     
> > >>>>>>         
> > >>>>>>             
> > >>>>> OK, makes sense.
> > >>>>>
> > >>>>> You could mount --bind the filesystem at the other location
> > >>>>>       
> > >>>>>           
> > >>>> instead of
> > >>>>     
> > >>>>         
> > >>>>> symlinking.
> > >>>>>
> > >>>>> The filehandles given to the client will be the same
> > >>>>>           
> > >> across the two
> > >>     
> > >>>>> exports.  If you mount both from the same client,
> > >>>>>           
> > >> behavior may vary
> > >>     
> > >>>>> across different clients (for example, as to whether they
> > >>>>>       
> > >>>>>           
> > >>>> attempt to
> > >>>>     
> > >>>>         
> > >>>>> share caches between the two), but I think it'd work.
> > >>>>>
> > >>>>> (The question "why??!!??" does come to mind, though.)
> > >>>>>
> > >>>>>   
> > >>>>>       
> > >>>>>           
> > >>>> Need to make a path change to how file systems are mounted and 
> > >>>> exported on the servers This then required a wholesale change to 
> > >>>> clients so they mount  the correct path.
> > >>>>  Not an issue for linux.
> > >>>> But since we don't administer windows pcs and they also 
> > mount the 
> > >>>> same file system, wanted to see if we could let them 
> > stay the way 
> > >>>> they were for now.
> > >>>>
> > >>>> We're just going to go ahead and  have to coordinate this with 
> > >>>> windows guys.
> > >>>>
> > >>>> -Sev
> > >>>>     
> > >>>>         
> > >>>>> --b.
> > >>>>>
> > >>>>>   
> > >>>>>       
> > >>>>>           
> > >>>>>> -Sev
> > >>>>>>
> > >>>>>> J. Bruce Fields wrote:
> > >>>>>>     
> > >>>>>>         
> > >>>>>>             
> > >>>>>>> On Fri, Nov 07, 2008 at 12:44:25PM -0500, Sev Binello wrote:
> > >>>>>>>   
> > >>>>>>>       
> > >>>>>>>           
> > >>>>>>>               
> > >>>>>>>> Can anyone tell me if it's ok to export the same file system 
> > >>>>>>>> through 2 different paths ( one is a link) ?
> > >>>>>>>>     
> > >>>>>>>>         
> > >>>>>>>>             
> > >>>>>>>>                 
> > >>>>>>> I actually don't know.  You could try it and tell us what
> > >>>>>>>           
> > >>>>>>>               
> > >>>> you find
> > >>>>     
> > >>>>         
> > >>>>>>> out....
> > >>>>>>>
> > >>>>>>> If you're exporting something *containing* the symlink
> > >>>>>>>           
> > >>>>>>>               
> > >>>> and expecting
> > >>>>     
> > >>>>         
> > >>>>>>> the client to traverse into the filesystem, be aware that
> > >>>>>>>           
> > >>>>>>>               
> > >>>> symlinks
> > >>>>     
> > >>>>         
> > >>>>>>> over NFS are actually interpreted (and followed) on the
> > >>>>>>>           
> > >>>>>>>               
> > >>>> client--so
> > >>>>     
> > >>>>         
> > >>>>>>> they're interpreted as *client-side* paths, not server-side.
> > >>>>>>>
> > >>>>>>> If the path you're exporting is itself a symlink--it probably 
> > >>>>>>> depends on how nfs-utils treats symlinks found in
> > >>>>>>>           
> > >>>>>>>               
> > >>>> /etc/exports.  I'd
> > >>>>     
> > >>>>         
> > >>>>>>> have to try it or check the code.
> > >>>>>>>
> > >>>>>>> Another way to export the filesystem in two different
> > >>>>>>>           
> > >>>>>>>               
> > >>>> places would
> > >>>>     
> > >>>>         
> > >>>>>>> be with mount --bind.
> > >>>>>>>
> > >>>>>>> --b.
> > >>>>>>>   
> > >>>>>>>       
> > >>>>>>>           
> > >>>>>>>               
> > >>>>>> --
> > >>>>>>
> > >>>>>> Sev Binello
> > >>>>>> Brookhaven National Laboratory
> > >>>>>> Upton, New York
> > >>>>>> 631-344-5647
> > >>>>>> sev-IGkKxAqZmp0@public.gmane.org
> > >>>>>>
> > >>>>>>     
> > >>>>>>         
> > >>>>>>             
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> > >> --
> > >>
> > >> Sev Binello
> > >> Brookhaven National Laboratory
> > >> Upton, New York
> > >> 631-344-5647
> > >> sev-IGkKxAqZmp0@public.gmane.org
> > >>
> > >>
> > >>     
> > 
> > 

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