feature or useful bug?
izzyb at ecn.ab.ca
Sun Jun 22 00:39:34 PDT 2003
I've been experimenting with building some new profiles and discovered an
unexpected behavior. I accidently created an entity with the same name as
another. This didn't produce an error or warning as I would have expected.
Instead it silently chose the first occurrence of the entity and ignored the
future occurrence. Somehow I don't think this is a _feature_ (at least I
don't recall seeing it documented anywhere), but it occurred to me that it
could be very useful behavior.
One thing I've been experimenting with is trying to build profiles in such a
way that they can be used either on their own, or as building blocks for
other profiles. In this way, a number of profiles from a variety of sources
can be used to build a system with the desired features. My hope is to come
up with a system that makes profiles easier to build for specific needs and
more practice to share with others. One problem that I've run into is how to
make a small change to a profile for a specific need, without needing to
duplicate and modify the original.
For instance, what if I want to load Grub instead of lilo (I don't, this is
just an example) using Naven's LFS4.0 profile included with nALFS? To avoid
duplicating and modifying the whole profile, I would create an alternate for
LFS-4.0.xml, so I could create an alternate for entities/system, so I could
specify an alternate for chapter6/lilo.xml to either load grub instead or do
nothing if I had an different profile loading grub.
If I take advantage of this _bug_, all I need to do is create an alternate for
LFS-4.0.xml (which I'm doing already so I can load other profiles) and load
an entity which override anything I need to change, before loading the
standard profile entities. Besides being simpler, this approach isn't likely
going to need modifying when you change to the LFS-4.1 profile once it comes
So, why am I telling you all this? Well, besides hoping it is usefull to
others, I want to make sure that this _bug_ is considered a _feature_ in
future development. ie, I'd hate to see it get fixed! :) It may be usefull
however to cause a warning to be displayed unless a command line flag is set
to ignore them. That way, people wont get bitten if they accidently
duplicate an entity name like originally happened to me. It took my a little
while to track down the problem when things weren't working as I expected! :(
PS: I plan to eventually make my profiles available to anyone who is
interested. I'm currently working on an LFS-4.1 profile which uses this
technique to override Naven's LFS-4.0 profile. I'm installing a system with
it right now. If all goes well, I'll make it available by request until I get
around to putting up a web site it can call home.
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