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

[Sev Binello <sev-IGkKxAqZmp0@public.gmane.org>]

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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