There's no real reason not to, so long as you're not using any software that is unsupported on Ubuntu Server.
We run CentOS because it's got binary compatibility with RedHat Enterprise, which a lot of commercial software releases packages for. It makes my life easier, and it's really pretty stable (not that Ubuntu isn't).
If you know Ubuntu, go with Ubuntu.
I've been searching the web and one
solution seems to be making a
kickstart script that will intall only
the necessary packages. But I find
this difficult and have several doubts
about how to maintain the system
dependencies afterwards.
Making a kickstart file is not so hard: look in /root of one of your installed servers for a file called anaconda-ks.cfg. That is a kickstart file to make a new server looking like the existing one. Every RH, Fedora or CentOS server has that file.
You can edit the file in system-config-kickstart if you are unfamiliar with writing kickstart files. You do need X for that though.
How do you install minimal Red Hat
servers? Is it Ok to use kickstart or
will I have dependency problems in the
installation or in updates? Is there
any way to avoid installing the
graphical environment for iAS?
You are doing fine with a kickstart file. Kickstart do affect the way you update after installation. During installation, dependencies are calculated automatically. Packages you removed (if that is at all possible) that are needed anyway are added. You cannot install a system with broken dependencies for the system. Dependencies for Oracle is a complete different matter though.
If Oracle needs a graphical environment (and it does, I know it sucks, but it does), you have no option but to install X. However, afaik, Oracle needs X because it has a graphical installer. You do not need X afterwards. So after install, you can remove X.
In my shop we only install a very minimal set of X libraries, btw. Just enough to run xclock (and thus the installer) remotely with X forwarding. That's enough.
Oracle has more insane dependencies. There are some ancient C library compat packages the Oracle installer needs. Not because it actually needs them, but because the zip implementation they ship needs them. Why do they ship that zip implementation? Rumor has it, that the very old zip implementation Oracle ships has more favorable licensing terms (as in: it's not GPL'ed), so they refuse to use a newer implementation. Just rumors though, never heard confirmation...
Best Answer
In my experience, the only two Linuxes that are taken seriously by the corporate world are Red Hat Enterprise Linux (RHEL) and SuSE Linux Enterprise Server (SLES). Everyone else is an also-ran for serious production work. You might find others on the desktop, but not on the money-makers.
That said, there are many non-Linux UNIX platforms that are also very valuable to know: the BSD family, Solaris, HP-UX, etc.