For natty there was a tool to configure automatic login and default session. It was called 'gdmsetup' and it would write out a GDM custom.conf for the user.
Oneiric doesn't provide any such tool. If a user configured automatic login at install and changed their mind, they would need to manually edit a lightdm configuration file by hand.
For people on natty who had automatic login enabled, the feature will be lost on the oneiric upgrade (due to bug 854431) and they won't be able to change it with any GUI tool.
ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: lightdm 1.0.0-0ubuntu4
ProcVersionSignature: Ubuntu 3.0.0-12.19-generic 3.0.4
Uname: Linux 3.0.0-12-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 1.23-0ubuntu2
Architecture: amd64
Date: Wed Oct 5 19:28:13 2011
DistributionChannelDescriptor:
# This is a distribution channel descriptor
# For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
canonical-oem-somerville-oneiric-amd64-20111004-0
InstallationMedia: Ubuntu 11.10 "Oneiric" - Build amd64 LIVE Binary 20111004-03:17
ProcEnviron:
LANG=C
SHELL=/bin/bash
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)
thank you for your bug report, the autologin is an option of the user-account configuration dialog in Oneiric, not sure the default session would be worth a separate dialog or a lightdm issue, that should be integration somewhere in the desktop