How do software updates work?

For your information, sudo apt-get update does not update software. It merely updates the list that the APT package manager uses to keep track of the software installed on the system, and the software available for the system from Ubuntu's repositories.

The correct procedure for updating to the latest version available in the repositories is to run sudo apt-get update to update the available software list, and then sudo apt-get upgrade to actually install the new versions of the packages.

It's worth noting that the versions in the repositories might be slightly outdated: this is typically because this is the only version Canonical is supporting for this release of Ubuntu, or because no-one's uploaded the new version to the repositories yet. You're welcome to install more recent software manually or using Personal Package Archives (PPAs.)

Ubuntu has a policy where (usually) only small security fixes to programs will be updated in the Ubuntu repositories (that you access through apt-get).

This is to ensure maximum stability in production enivronments - this is particularly important on servers. This means you won't see version updates to software such as PostgreSQL and Nginx until Ubuntu Server 11.04 is released.

You can find out information on the Ubuntu wiki about Stable Releases Updates.

With apt-get you will only received the latest version that the Ubuntu team supports. If it is not your desired version, you will also not receive it with this release as there will be no major version upgrade within a release.

So you either have to wait for a new Ubuntu release and hope they upgrade your package or build and install it yourself manually. With the loss of automatic updates as well.

You could also try to find the newest version in the Debian unstable branch or wait for Ubuntu to implement Backports for Maverick.