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Why Elektra is the wrong approach (Was Re: The Strengths and Weakness of Fedora/RHEL OS management)




On Mar 29, 2006, at 7:29 PM, Avi Alkalay wrote:

In addition to the words bellow, the "D" on D-Conf comes from the "Desktop" word, which means D-Conf is a desktop-oriented wannabe- project. You won´t be able to standarize configuration for say named, dhcpd, resolver, sysctl, modprobe, /sbin/init, network configurations, etc etc etc with it.

Speaking of wanna-be. I think one fundamental problem with the LinuxRegistry/Elektra approach is that you try to fix the symptoms of the problem instead of the root problems. I've written about this before and I will do it again and again as apparently people are still trying to fix the symptoms of our problem:

 Configuration of software in a mainstream distribution is a mess.

Most of this mail is about the desktop, but really, if you look at it, desktop is _a lot harder_ than server (there is just so much more code and so much more functionality) so my view is that if we solve it for desktop then the server bits will pan out mostly by itself.

It seems that Elektra simply wants to remap the configuration file for a piece "software" into a hierarchical key/value database and I think that's missing the point entirely. First of all you got to ask yourself whether there should be a configuration of said piece of software in the first place. If you think really hard about it you will find that for most pieces of software this is false - you really don't want any configuration files... Hence you really don't want nor need Elektra.

Let us look at what "configuration" really means; I've seen it being used in the following ways

- The programmer is lazy and makes the user look up configuration values he could have determined programmatically - for example this includes the laptop_mode scripts where you can configure what IDE drives to put to sleep. The poor user will have to put in arcane values such as "/dev/hda", "/dev/hdd" and so forth. You know, maybe the laptop_mode developer wasn't that lazy, maybe the kernel people was just sleeping and gave him no easy way to find out what drives to put to sleep when he wants.. or maybe what the kernel said was unreliable and the kernel never got fixed.... Does this justify bothering the poor end user with crap like this? I think not.

- Configuration can be system-wide, for example mail and web servers... Sure, my web server needs to know where to serve files from, my mail server needs to know what domain it serves and so forth

- When developers write a daemon and decide to make it system-wide, then most of the time they either really want it to be site-wide or session-wide instead. Most of the time they don't even know this... I will argue that system-wide is just plain wrong for most things; continue reading...

- Site-wide software: This includes for example a cluster of web servers. The user experience if I'm an administrator is that I can just plug in another physical server box, PXE-boot it and it reads all "web server configuration" from LDAP. If it blows up I can replace it. Hence, no need at all for having some httpd.conf file. For the (terribly uninteresting) case of only having one machine as a web server it reads settings from the local LDAP server. Ditto with mail servers, name servers etc.

- Session-wide software: Just so we're all on the same page, "session-wide" means something that runs in a user desktop session. Historically, the desktop wasn't very advanced and didn't integrate well with the system. Back then things that really was session-wide would run as a system-wide daemon mostly also because it required root to enforce policy. Things like acpid for power management event handling, updfstab for removable media, ifplugd for handling network cable removable, networking scripts etc. comes to mind. As you can see with Fedora Core 5 this is radically starting to change; acpid is obsoleted by gnome-power-manager, updfstab (and fstab-sync for that matter) is obsoleted by gnome-volume-manager / gnome-mount, the networking scripts is starting to be completely obsoleted by NetworkManager. We have more things on out "hit list"...

- You really really want session-wide daemons to run in the session and not as the system because it's much easier for the user to configure it.. in fact, you get per-user settings for removable media handling and power management in FC5. And since all this is backed by gconf it's easy for the OS vendor _and_ the administrator to set sane defaults, lock things down and so forth. It's just a lot better

- Look at the terrible and insecure hacks for writing out configuration files for system-wide daemons that ought to be session- wide. See also my rant on fedora-maintainers last week why consolehelper (that these tools rely on) is fundamentally flawed.

- Things like smb.conf is really not interesting for the desktop case as it's the wrong solution to the problem of sharing files and using files other systems wants to share. The right answer here is obviously things like Nautilus and gnome-user-share and other things that run in your session and is easy to configure.

- X.org having a configuration is completely broken too; obviously the X.org server should be able to configure itself (and it can but X.org itself has bugs so it doesn't always work) and it should offer a D-BUS interface for reconfiguration so some per-session piece of software can program it with the users setting when your session starts. Yes, display configuration is also per-user although the brain dead design of X.org doesn't reflect this.

I don't have a good answer to KDE and GNOME sharing configuration; I personally think that as this point it's impossible to get developers of both camp to agree on a scheme for even simple things like desktop backgrounds and HTTP proxies. And should the day come when gconf depends on KConfig, vice versa, or when there is D-Conf I'm sure this will get solved by itself. It sure as hell doesn't need Elektra for this.

So my message is that I think it's a waste of time trying to shoehorn a configuration file format onto all kinds of software because said software is likely to be already broken for at least desktop use. My stance is simply that it's unacceptable in a desktop system to ever ever have to touch a configuration file and I think some people (*cough* Apple *cough* Microsoft *cough*) take the same stance even for the server. So we shouldn't ship software that rely on them. Hence, there is zero need for Elektra. It's really that simple if you think about it.

I wish that people working on the server bits (e.g. Apache, Postfix) would take a similar stance and only make their software read settings from LDAP (or whatever) for the site-wide case. I think it would be great if you could change Elektra into something that would fix this. But please back off trying to pretend you solve problems for the desktop because you're not. The design of gconf is pretty nice (implementation might be another matter but, you know, that's totally fixable) and it's more than sufficient for desktop use, thank you very much.

Hope this clarifies why Elektra is simply the wrong answer. I'm sorry for sounding harsh and saying most of our software in the distribution is broken, but it's kinda this conclusion I've arrived at. We could do so much better if we all tried to solve the root problems and look at what the user experience should be.

Have a nice day.

    David

Disclaimer : this mail doesn't necessarily reflect the views of Red Hat, Inc.



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