[mwcampbell]

I think a big reason why Ubuntu is so popular for cloud deployments is that Canonical provides official Ubuntu images for Amazon EC2. Last time I checked, CentOS didn't. Red Hat does, but of course, you'll pay extra to run official RHEL, so that probably makes it less attractive to a lot of companies. Basically, Ubuntu is the path of least resistance on EC2.

My employer used RHEL on its servers (via a managed hosting service) for about a year, and it left a bad taste in my mouth, especially because RHEL5 was still on Python 2.4, and I needed a newer Python for some things. Sure, I was able to install a newer Python in /opt/python2.5 and move on. But when we left the managed hosting service and it was time for me to choose the OS for our next servers, I went with Ubuntu, because I knew it would have newer software, including (by then) Python 2.6. Another factor, to be sure, is that I've been using Debian and Ubuntu sporadically since Debian 1.1 or 1.2 in 1996. So Ubuntu was quite comfortable for me. The same factors probably figure in other admins' decisions too.

No argument from me about yum versus apt; they both do the job. Actually, these days I think that Debian (and by extension Ubuntu) overreaches in some ways, with Debconf and automatic startup of services after installation, whereas the Red Hat distros leave configuration and service startup after initial installation to the admin. So there's no clear winner; they're just different.

[mindcrime]

I think there are CentOS official AMIs now. Not sure how long that's been the case, but their wiki suggests that such "official" images do exist.

http://wiki.centos.org/Cloud/AWS