Use of multiarch is not currently enabled by default on any architecture because of, among other things, an impact on the performance of 'apt-get update'.  Users can manually enable multiarch in oneiric by doing the following:

 * Create a file {{{/etc/dpkg/dpkg.cfg.d/multiarch}}} containing a line {{{foreign-architecture $arch}}} for the ''$arch'' of interest
 * If different mirrors are needed for the main arch vs. the foreign arch (e.g., archive.ubuntu.com vs. ports.ubuntu.com), add lines to {{{/etc/apt/sources.list}}} like this:
{{{
deb [arch=armel] http://ports.ubuntu.com/ubuntu-ports/ oneiric main
}}}
 * run apt-get update
 * install packages, specifying the architecture as {{{:$arch}}} after the package name:
{{{
sudo apt-get install libxext-dev:armel
}}}