*** This bug is a duplicate of bug 1514149 *** https://bugs.launchpad.net/bugs/1514149
Thanks Phillip, Jan, and everybody else who offered help. And especially thank you Jan (janh2) for pointing out the toram bug. This seems to be exactly the problem: when i removed "toram" from my grub menu item, i didn't encounter the same issue i had before. I did encounter another issue, later in the process, because the installer wants to umount all partitions on the drive containing the partition ubuntu is to be installed to. That's a problem when you're using a loopback source (i.e., the iso image on disk rather than DVD). But that problem can be overcome by installing to a different disk drive. That solution worked for me, although of course it would be a fail for anybody with only one disk. So i think the toram bug is serious, and if there actually is a launchpad bug report filed for it, i can go click on the "affects me too" link. (So somebody please enlighten me if so.) Thanks again everybody for your help! -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1509603 Title: apt configuration problem in 15.10 installation (failed "to install additional packages") To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1509603/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs