[AG-DEV] Re: Location of AG config files

[Christoph Willing]

On 12/09/2008, at 5:41 PM, Tobias Schiebeck wrote:

> Hi,
>
> Beeing a Debian user for some years now, I know that Debian has
> sometimes strange ideas how to package things. On the other hand I was
> slightly surprised to find "code" such as the SharedPresentation
> implementation under /etc . IMHO /etc is the place for config files  
> and
> thats what I think Debian is trying to enforce (which I don't think is
> the right thing to do but ...)
>
> On Thu, 2008-09-11 at 07:55 -0500, Thomas D. Uram wrote:
>> Chris:
>>
>> What's the chance that a future change will also impact files under
>> /usr/share, requiring another adjustment?  Is there any guidance from
>> the debian/ubuntu community about how to adjust, or where such files
>> should be placed?
>>> (One way around this would be to create a single mega-package of  
>>> AG &
>>> related service packages, but I feel it would be an unsatisfying, if
>>> not "wrong", solution)
>> I agree that this is not the right way to go.
>
> I think /usr/share is where the NodeServices and other "code"  
> should be
> placed and should be fairly safe from changes. The pure configuration
> files such as the nodeConfig could stay under /etc as it would be
> recreated if it isn't there, and /etc is the place where people  
> look for
> these general configuration stuff.


I agree that this is the correct way to go.

However splitting these files into separate locations entails more  
work to implement compared with having them all in /etc or all in / 
usr/share - having them all in one place means just a single line of  
code needs to be changed (the definition of AGTkBasePath).

If we now have a separate location for some of the files (I suggest  
the Services, NodeServices and SharedApplications directories), then  
we'd need not just an additional variable defining the new location,  
but also changes to any current code which assumes the old locations.  
For instance, convenience functions like GetSharedAppDir() themselves  
call GetBaseDir() which would now return the wrong location;  
something to replace GetBaseDir() is needed in all these cases.


If we decide to go ahead with something like this, the next question  
is who will implement it? I'm prepared to do it but the changes touch  
on reasonably fundamental bits of AG internals so perhaps it is best  
left to Tom ... ?

Either way, Debian Lenny is currently frozen in the lead up to being  
released. It would be good to have any AG changes fully in place by  
the time Lenny is released.
Similarly, Ubuntu 8.10 is due in October.


chris



>> On 9/8/08 6:37 PM, Christoph Willing wrote:
>>> Tom,
>>>
>>> There is a problem with the Debian & Ubuntu AG packages. The  
>>> revamped
>>> build tool mechanisms introduced early this year to accommodate
>>> multiple python versions on the same machine has an unfortunate side
>>> effect; anything under /etc is considered to be owned by a  
>>> particular
>>> package and is removed completely during upgrades or  
>>> reinstallations,
>>> regardless of whether another package may be using the same area.
>>>
>>> In the case of the AG installation, a number of configuration files
>>> are kept in directories under /etc/AccessGrid3. In particular,
>>> /etc/AccessGrid3/NodeServices normally contains the standard Audio &
>>> Video Services. However other packages may want to install services
>>> there too e.g. vpcscreen, aghdvic. Initial installation of these
>>> packages works OK but if the AG package is reinstalled or upgraded,
>>> the additional services are also removed.
>>>
>>> (One way around this would be to create a single mega-package of  
>>> AG &
>>> related service packages, but I feel it would be an unsatisfying, if
>>> not "wrong", solution)
>>>
>>> This (new) unwanted behaviour occurs because of the special  
>>> treatment
>>> given to files/directories under /etc, so an solution is to use a
>>> different location. I have done some testing using
>>> /usr/share/AccessGrid3 instead of /etc/AccessGrid3 as a location for
>>> the config files. With this new location, any number of  
>>> installations,
>>> reinstallations etc. of the AG  & related packages can now be
>>> performed without any interference to each other. Introducing the  
>>> new
>>> location is trivial - a single line patch to the toolkit code  
>>> itself,
>>> as well as a single line change in the packaging script of each
>>> affected package (accessgrid3.x, vpcscreen, aghdvic, etc.)
>>>
>>>
>>> Since this is a Debian & Ubuntu specific problem, I don't expect  
>>> that
>>> relocating /etc/AccessGrid3 needs to apply to all distributions
>>> (although it may be worth considering). However before I release any
>>> packages with the new file layout, do you have strong feelings about
>>> the proposed solution - or alternative solutions?
>>>
>>> I've cc'd to AG-DEV in case someone more conversant with Debian/ 
>>> Ubuntu
>>> Policies & packaging practices can offer advice; please chime in  
>>> - I'm
>>> just a part-timer in this area and I'm keen to receive suggestions.
>>>
>>>
>>>
>>> chris
>>>
>>>
>>> Christoph Willing                        +617 3365 8350
>>> QCIF Access Grid Manager
>>> University of Queensland
> -- 
> ---------------------------------------------------------------------
> Tobias Schiebeck                    tobias.schiebeck at manchester.ac.uk
> Research Computing Services           http://www.rcs.manchester.ac.uk
> The University of Manchester                  tel: (+44) 161-275-0601
> ---------------------------------------------------------------------
>
>

Christoph Willing                        +617 3365 8350
QCIF Access Grid Manager
University of Queensland