Re: configuration files

[Galen Sampson <galen_sampson@xxxxxxxxx>]

Matthew Dillon wrote:
>     I personally prefer NOT to use XML for something like this.  I just
>     don't see the point... all it does is add reams of API junk that all
>     devolve down into accessing some variable or other.

I have 3 bsd machines at home.  I want to be able to manage all of them 
as easy as I manage 1.  The scripts that you wrote for diskless boot is 
a good idea.  It has some drawbacks.  You can only do a full override of 
an entire file.  You mention the ability to do sh programming in 
rc.conf, and this could be used to get around doing a full override but 
that isn't a great option.  I want to be able to have a set of default 
variables for all machines.  I want to then be able to modify only the 
variables I need to override.  If I did this with sh if [ ... ] the 
rc.conf file would get complex and ugly.  Then there is the option to 
put each .conf file in /etc/rc.d/*.  So /etc/rc.d/sendmail.conf for 
instance.  I've looked and I think rcng is set up this way already.  XML 
would solve the problem of setting specific variables in a file, no 
matter what order the variables are listed.  XML also has an import 
statment so you wouldn't need to use cpp to import separate files.

I have tried putting my config files in cvs.  Then I try to merge the 
default file into the machine specific override.  I didn't get it 
working right.  I didn't know about the Infrastructure project 
http://www.infrastructures.org.  The fact that my idea is not unique is 
a good thing.  Maybe they solved some of my problems already.

>     The /bin/sh variable=data form is probably as powerful a mechanism as
>     we would ever need, especially when combined with autoconf-like mechanisms
>     such as, for example, access to the DHCP variable space.  In fact, it
>     occurs to me that we could augment 'kenv' to allow setting kernel 
>     env variables in addition to retrieving them and use the space to store
>     DHCP and/or autoconf variables.  That would be pretty damn cool.  Then
>     /etc/rc.conf could be trivially conditionalized.

What are autoconf variables?  Variables obtained automatically I guess 
(not the autoconf build system).  What else provides this besides DHCP?

Regards,
Galen