With an installfest approaching (back on 04 August) and being devoid of Canonical flash drives to distribute to the new people who always show up and want to have Ubuntu installed on their computer, a conference pack was ordered from Canonical which would include the flash drives as well as other swag to be distributed to new converts. The conference pack arrived well before the installfest date (on 25 June) but the flash drives were of the 16.04 variety. Since 18.04 had been released on 26 April, we wanted to install the latest and greatest. With experienced people on hand in Sierra Vista we split the task of creating the Ubuntu 18.04 install media on the newly arrived Canonical flash drives. At the installfest five of the 25 flash drives were used to attempt to install Ubuntu on a Mac-Mini. All five installed Ubuntu 18.04 but failed to reboot after the flash drive was removed. This gave us cause to believe that perhaps the flash drives were not any good or could not be rewritten with a newer version in them. Not likely because we had been rewriting them as each point release came out for Ubuntu 16.04.
After the installfest three additional Canonical flash drives were used to attempt an install on a Dell Opti-Plex. The result was the same. The 18.04 ISOs had been downloaded using torrent so the hashes had not been checked prior to the installfest or being written to the flash drives. However after so many had failed, they were checked (SHA256SUM) and the hashes matched. In addition the Ubuntu 18.04.1 ISO was downloaded (again using torrent and the hashes again matched). Ubuntu 18.04.1 was used to create install media on three Canonical flash drives. They were also used in an attempt to install on the Dell Opti-Plex but failed after the install and reboot just before the user login appeared. This was the same result as the 18.04 flash drives.
In an attempt to eliminate possibilities, Ubuntu 16.04.4 was written to a flash drive and attempt to install was made. In this case it was successful. Now it was assumed that the Canonical flash drives would not allow the 18.04 version. This was quickly disavowed when the 18.04 versions of Lubuntu, Xubuntu, Kubuntu, Ubuntu Mate, and Ubuntu Budgie were downloaded and placed on Canonical flash drives using Startup Disk Creator. In turn each was successfully installed on a partition and rebooted. So it could not possibly be defective Canonical flash drives.
Several personal flash drives were made available and Ubuntu 18.04.1 were placed on them using Startup Disk Creator. Once again each installed on the Dell Opti-Plex but the screen would freeze just prior to the login appearing after the withdrawal of the flash drive and reboot, the same location it had always been freezing. Not to be outdone and to cover all bases, an installation with nomodeset was attempted with the same result. One article on the internet suggested that instead of writing over partitions that perhaps they should be deleted prior to the install. This didn’t really make any sense but it was tried as well with the exact same result. Running out of options, a minimal install was tried and once again we had an installation but a screen freeze prior to the login. In many of these cases the option of Try Ubuntu was activated before installing. Also the icon on the Desktop as well as the icon in the Dash were used.
The problem or little quirk was submitted to the Ubuntu Forums and drew a response of “full Ubuntu is now really for newer systems as GUI needs better gpu and system”. Well, so is Kubuntu which is just as robust if not more so than the mother distro. The problem remains. Why will Ubuntu 18.04 (and 18.04.1) not reboot after an install on some computers that meet the minimum requirements for installation.


After much searching, I discovered that Ubuntu 18.04 was released with a new login display manager, gdm3, which is a apparently much heavier than its predessor, LightDM. It may be causing the 10 plus year-old desktop to "choke under the load of starting gdm3 when it is booting Ubuntu 18.04." A solution was found here,
By installing LightDM and making it the default login display manager, 18.04.1 (now) boots normally.