- Package installation procedure - when a list of packages is being installed or upgraded, Debian package manager or DPKG does this procedure in stages. That is it will first unpack all the packages, then run all the pre-install scripts, then install the files, then run the post-install scripts etc. (I am not trying to be correct about the exact steps here). And while this behavior might seem logical therein lies a problem. If, for example, one of the packages' post-install scripts fails, dpkg reports a problem and quits and all the rest of the packages remain unconfigured. True, dpkg will continue where it left off when the suer resolves whatever problem is causing the script to fail or removes the offending package, but this is not the point. Lets consider a case where actual updated package is broken and script fails because of a syntax error. Once dpkg fails the system ends up in rather strange state. All the services that were to be updated were stopped, but weren't started again (since that happens in the post-install). New libraries were unpacked, but ldconfig weren't run. New kernel might have been installed, but new initrd wasn't generated and boot manager wasn't updated. Basically we have a broken system that needs careful fixing by a specialist who knows what he is doing. And even if you do know what you are doing, your choices are limited. You need to either fix the script yourself, repackage and reinstall, but that makes your system somewhat inconsistent or you need to completely remove the package, rerun dpkg to finish the install/upgrade of other packages in the queue and try to reinstall the old version back, but that might not be possible since all the other packages might prevent the old version from being installed, so you need todescend the dependency hell and start selectively uninstalling and downgrading packages to get a working version of whatever software. Yes, some of it is also true about RPMs, but at least when one of the RPM installs fails all the rest of the packages are either NOT installed or installed COMPLETELY nothing except possibly the broken package is done half way.
- Package state markings - as I mentioned in previous paragraph, when dpkg fails to do some of its tasks it can be rerun and will proceed from the point it stopped (or fail in the same place). This is done by having very granular records of package state. APT seems to like to mark packages just a little bit too much and annoys its user. Lets say, I have started an install of a package that needs a 100MB of dependencies and suddenly I need to go somewhere. So, I hit CTRL-C, close the laptop and run out. Later I find that my laptop doesn't have a reader of some sort installed, for example FB reader and I need it right away to read some document. I hit apt-get install fbreader, but suddenly the whole 100MB of stuff starts downloading again. Why? Because APT marked all those packages for installation and will install them unless they are unmarked. Honestly I don't know how to easily unmark packages marked for install/upgrade short of doing dpkg --get-selections, manually editing the resulting list and piping it into dpkg --set-selections. There maybe a way to do this using GUI interface such as synaptic, but at a glance I couldn't find it. Other example of this "feature" is when you are trying to remove packages. Sometimes you see a package and think "I don't need this, why is it installed", so you dpkg -P it. And suddenly dpkg tells you, that the package is actually a dependence of something or other. But although dpkg proudly reported that it did not remove the package in question because of dependency problems, it DID however mark the package as "to be removed", so if ever the dependencies change this package might just disappear without any intervention.
- SysV scripts - Debian like most other Linux distros uses SysV startup. One feature though seems to be specifically done to annoy the hell out of the user. Every time a service that has a startup script is upgraded, it automatically setup to start at boot. Even if it was manually turned off before. In Fedora I can say chkconfig httpd off and Apache will not start until I say otherwise. On a less sophisticated system I can say something like rm -f /etc/rc?.d/S*httpd to achieve the same result. On Debian I can update-rc.d -f remove apache, but once an upgrade to the apache package is installed it will reinstate itself on its default runlevels and happily start on boot. As far as I know, there is NO way to prevent this. Ridiculous.
- Package management command set - this is not as much a problem as a way to a lot of confusion and it is not restricted to the package management system. There is just too much legacy in the Debian native commands. The package system provides a very good illustration. In Fedora I generally use two package management commands, yum and rpm. Yum mostly works with remote repositories and handles package installs, upgrades etc. RPM works with locally installed packages and manages installing from local file, querying the package DB, removing packages, package signing keys etc. In Debian it is not as simple. To install from remote repositories I use either apt-get. To search remote repositories I use apt-cache. To install from local file or remove package I use dpkg. To query package database I use dpkg-query. To manage keys I use apt-key. Each of these has its own specific subcommands and flags.
- DEFOMA - the Debian Font manager. Basically this is a convoluted something that is supposed to make all the font management automagical. Unfortunately all it seems to do is confuse anyone who tries to figure out what happens to fonts on the system.
Friday, March 14, 2008
Why I don't like Debian based distributions.
I have been happily using Fedora for a while now, but I keep a close eye on Ubuntu development, since it is my humble opinion, that nothing, at the moment, compares to Ubuntu in ease of use, hardware compatibility and general togetherness. I recommend Ubuntu to people who want to try out Linux, I ran Ubuntu myself for a while, I run beta versions of Ubuntu releases and file bugs (well, when I have time). Now I also have an Eee PC laptop running Ubuntu. I like Ubuntu. But I run Fedora as my main OS. The reason for this is Ubuntu being Debian derivative and as such dragging with it all the horrible Debian legacy. I honestly wish Ubuntu chose a different What is horrible about Debian? Well, this post intends to list a few things that annoy the hell out of me and that IMHO should have been fixed ages ago. Yes, I am aware, that I blaspheme.
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