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DragonFly kernel List (threaded) for 2003-12
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Re: configuration files

From: James Frazer <jfrazer@xxxxxxxx>
Date: Fri, 12 Dec 2003 16:11:40 -0600

I agree -- XML should not be used for the files in /etc/rc.d ... That's a bad idea -- but I don't really think those can be classified as configuration files -- as they are control scripts, right?

I'm not entirely sure how rc.d got into all of this.

Commenting on *nix configuration files in general I think it's safe to say that there's lots of unnecessary diversity. For example -- some configuration files are very specific with key/value pairs.


Where as other files -- such as /etc/passwd use an implied system where the key/value (so to speak) connection depends upon which field/column the data is in (and the key is not even stated).

And there are many other forms of syntax. In /etc/passwd the fields are seperated by colons. In /etc/fstab the fields are seperated by whitespace. /etc/gettytab uses termcap (I think).

In some configuration files multiple values are seperated by whitespace, in others they are seperated by commas, etc, etc.

So if someone was ever to write an admin-frontend to any of these configuration files (where relevant) they would have one heck of a time sorting things out. And it seems as though every config file differs slightly from the next in some small way. Of course we can say many of these files don't need a frontend (as they probably don't), but can anyone see what I'm getting at here? Even just editing files by hand I've always been somewhat annoyed that everything is done differently -- often when it seems as though there was no foreseable need to be different in the first place. But I suppose until I code something better I should probably shutup. ;-)


Matthew Dillon wrote:

I think, ultimately, what matters is how things improve from a sysop's functionality and ease-of-use perspective. It's all well and fine to talk about the capabilities of XML, but there's no point if the capabilities aren't useful for the particular real-world task being contemplated (or, more to the point, more useful then what we could get out of RCNG's existing capabilities).

    RCNG is a great example of this.  RCNG already had the ability
    to 'start' and 'stop' subsystems, and RCNG already contains all
    the dependancy information required to deal with dependant subsytems.
    But how many people do you know actually go to the trouble of CD'ing
    into /etc/rc.d and running ./blah start and ./blah stop on a regular

    Even though it is not difficult to do the above, from an ease of
    use perspective there is a huge difference between doing the above
    and doing, say, a one-line 'rcstart subsystem_name' command as root.

But in less then a day I was able to make significant improvements
to the use of the meta-information embedded in the RCNG scripts
which enables rcstart/rcstop (and future work) to take advantage of
it in a manner that presents a simple, straightforward, 'easy to use' interface to the user/sysop.

XML would not make any of this work any easier. No matter what form
the data is in, you still have to process it in a manner that benefits
the target function. In the case of RC stuff that means dealing with
fairly complex dependancy graphs. In fact, XML would make the work
a whole lot harder. I wonder how many of you have actually *LOOKED*
at the files in /etc/rc.d ... some of those scripts do rather complex
things that really can only be done in a shell script. XML would only
add unnecessary layers of complexity and not actually allow us to remove any of the existing complexity. Another example: half the RCNG
scripts do not support 'stop'. Reimplementing in XML would not magically
cause 'stop' to be supported. In otherwords, you still have to do the
work required to implement the 'stop' function for those subsystems that
do not have it.

Matthew Dillon <dillon@xxxxxxxxxxxxx>

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