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

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

Since on the server side there  truly is only 1 export.
And clients just access the same export through  2 different names,
I expect it would be safe.

-Sev

ps: But I think I'll wait for a simpler application (less negative 
ramifications) to test it
     BTW haven't seen this documented anywhere.

J. Bruce Fields wrote:
> 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
>>>>>>>>>
>>>>>>>>>     
>>>>>>>>>         
>>>>>>>>>             
>>>>>>>>>                   
>>>>>>> --------------------------------------------------------------
>>>>>>> -----------
>>>>>>> This SF.Net email is sponsored by the Moblin Your Move 
>>>>>>>               
>>> Developer's 
>>>       
>>>>>>> challenge Build the coolest Linux based applications with
>>>>>>>         
>>>>>>>               
>>>>> Moblin SDK
>>>>>     
>>>>>           
>>>>>>> & win great prizes Grand prize is a trip for two to an 
>>>>>>>               
>>> Open Source 
>>>       
>>>>>>> event anywhere in the world 
>>>>>>> http://moblin-contest.org/redirect.php?banner_id=100&url=/
>>>>>>> _______________________________________________
>>>>>>> NFS maillist  -  NFS@lists.sourceforge.net 
>>>>>>> https://lists.sourceforge.net/lists/listinfo/nfs
>>>>>>> _______________________________________________
>>>>>>> Please note that nfs@lists.sourceforge.net is being discontinued.
>>>>>>> Please subscribe to linux-nfs@vger.kernel.org instead.
>>>>>>>     http://vger.kernel.org/vger-lists.html#linux-nfs
>>>>>>>
>>>>>>> --
>>>>>>> To unsubscribe from this list: send the line "unsubscribe
>>>>>>>         
>>>>>>>               
>>>>> linux-nfs" 
>>>>>     
>>>>>           
>>>>>>> in the body of a message to majordomo@vger.kernel.org More
>>>>>>>         
>>>>>>>               
>>>>> majordomo
>>>>>     
>>>>>           
>>>>>>> info at http://vger.kernel.org/majordomo-info.html
>>>>>>>
>>>>>>>     
>>>>>>>         
>>>>>>>               
>>>>> --
>>>>>
>>>>> Sev Binello
>>>>> Brookhaven National Laboratory
>>>>> Upton, New York
>>>>> 631-344-5647
>>>>> sev-IGkKxAqZmp0@public.gmane.org
>>>>>
>>>>>
>>>>>     
>>>>>           
>>>       


-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/
_______________________________________________
NFS maillist  -  NFS@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/nfs
_______________________________________________
Please note that nfs@lists.sourceforge.net is being discontinued.
Please subscribe to linux-nfs@vger.kernel.org instead.
    http://vger.kernel.org/vger-lists.html#linux-nfs