Comment 1 for bug 351556

This bug happens for frugal install of Ubuntu 8.10, 9.04 and 9.10. Ubuntu 8.04 is not concerned.

To reproduce the bug, install UNetbootin on windows and chose "frugal install" of Ubuntu (either of the concerned versions 8.10 or 9.04 or 9.10)
. Reboot and launch an installation of ubuntu. At the beginning of the installation process, you get this error message:

"
Failed to unmount partitions

The installer needs to commit changes to partition tables, but cannot do so because partitions on the following could not be unmounted.
/cdrom
Please close any applications using these mount points.
Would you like the installer to try to unmount these partitions again?
"

This prevents to go further in the installation.

Workaround: There is no workaround known.
Be careful, some internet forums suggest to unmount manually this '/cdrom' before starting the installation (with the command "umount -l -r -f /cdrom") ; but this will not work and may break your grub settings. I tried this on Ubuntu 9.04 & Ubuntu 9.10. The result is that indeed you can complete the install process but grub won't be correctly configured (basically it does not recognize neither ubuntu nor your current windows partition) and after a reboot grub won't show any boot menu and will keep on starting memtest.
You will have to restore your MBR if you want to access your windows partition again. (To restore your MBR, you will need a CD-ROM drive and an installation CD of Windows XP or Vista _Win7 may allow that also_. Boot on your installation CD and type 'R' to choose "restore" option. Once there use the command FIXBOOT and/or FIXMBR.)