Binary package hint: ubiquity
I booted a system without graphics acceleration from the Oneiric i386 20110526.1 daily-live CD. A blank blue desktop background was shown, with no other graphical user interface elements. I waited over 30 minutes, and no ubiquity-dm menu was ever shown prompting me to select my language and indicate if I wanted to Install Ubuntu or Try Ubuntu.
So I rebooted, and pressed Spacebar when the person and keyboard icons appeared at the bottom of the screen, to bring up the non-graphical boot menu. I selected English and "Try Ubuntu without installing". A blue desktop was shown, and very soon afterward the "Oh no! Something has gone wrong" screen came up, with Log Out as the only option. (I have attached a screenshot of this screen, in case there is any confusion about what I am describing.)
Upon logging out, I was able to manually change the session type to "Ubuntu Classic (no effects)" and log in to get a functional desktop. However, this is not obvious to non-technical users, which includes most users (who probably don't know that you *can* log on to a live CD system with username ubuntu and a blank password, and also probably don't know that you can select a session type at the bottom of the login screen while it is asking for your password).
In previous versions of Ubuntu (or at least Natty), this message (pointed out to itself be confusing in bug 683936, and quoted here from that bug) used to be issued:
"Sorry, you don't have 3d support, install it for your graphic hardware to get Unity or please reboot and select 'Classic session' at startup."
I recall that, in Natty, clicking OK (or maybe it was Close) in that message box would cause Ubuntu to provide a classic desktop automatically. So this bug could be summarized as consisting of two parts: (1) that a 3D session does not automatically fall back to be replaced by a 2D session (actually it does, in that the "Oh no! Something has gone wrong!" message is displayed by a window rendered by metacity, but this is not a functional session), and (2) that the ubiquity-dm menu does not launch, and without manually selecting an option from the non-graphical boot menu, all you get in Oneiric on a system without graphics acceleration is a blank desktop.
For the sake of thoroughness, I'll attach some log files that document the cause of the "Oh no! Something has gone wrong" error. I am reporting this bug from the 2D session, so the relevant lines are in /home/ubuntu/.xsession-errors.old:
Compiz (opengl) - Fatal: GLX_EXT_texture_from_pixmap is missing
Compiz (opengl) - Fatal: software rendering detected
There are other errors later in that file, but they appear to be from attempts to interact with the Compiz Fusion desktop that couldn't be started due to lack of hardware OpenGL support. I'll also attach /var/log/Xorg.0.log.old, to show that there didn't seem to be any other problem, as well as .xsession-errors and Xorg.0.log (from the new, good, classic session, for comparison).
ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: ubiquity 2.6.10
ProcVersionSignature: Ubuntu 2.6.39-3.9-generic 2.6.39
Uname: Linux 2.6.39-3-generic i686
Architecture: i386
Date: Thu May 26 21:07:12 2011
LiveMediaBuild: Ubuntu 11.10 "Oneiric Ocelot" - Alpha i386 (20110526.1)
ProcEnviron:
LANGUAGE=en_US:en
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)
I am beginning to wonder whether or not the blank desktop when ubiquity-dm (i.e., the graphical Install Ubuntu / Try Ubuntu selection screen) should have come up is really the same bug as the lack of automatic checking for 3D support and uninformative "Oh no! Something has gone wrong" error.
On a different machine with an ATi Radeon HD 5700 Series video card running the Oneiric amd64 20110526.1 daily-live CD, manually selecting "Try Ubuntu without installing" from the non-graphical boot menu yields a somewhat usable Unity desktop. (There are some serious usability bugs with Oneiric's Unity on this amd64 machine, which I hope to get around to searching for and, if unreported, report, sometime in the next couple of days.) However, booting normally (without bringing up the non-graphical boot menu) yields a blank, nonfunctional desktop instead of the ubiquity-dm window, just as on the i386 machine on which I originally reported this bug.
Should I split this bug report and create a second bug? I can edit the description to remove the text about the blank screen when ubiquity-dm should appear, and file a new bug about that problem.