Ubiquity presents unhelpful error dialog after "Preparing to Install" screen

[Rod Smith]

Ubiquity is producing an unhelpful error message (see attachment) on one of my test systems after I select "Continue" in the "Preparing to Install Ubuntu" screen. After dismissing this dialog box, nothing happens; the mouse pointer changes to a rotating circle of dots and the next screen does not appear. I'm attaching the /var/log/installer/debug file from a run of "ubiquity -d -b". (This problem occurs even without the -b option, though.) As the debug file seems to indicate a partitioning problem, here's my partition table, as seen from both parted and gdisk:

$ sudo parted /dev/sda print
Model: ATA WDC WD10EARS-00M (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt

Number Start End Size File system Name Flags
 1 20.5kB 315MB 315MB fat32 EFI System boot
 2 315MB 839MB 524MB reiserfs Ubuntu /boot
 3 839MB 1363MB 524MB ext2 Ubuntu 14.04 /boot
 4 1363MB 26.4GB 25.0GB ext4 Ubuntu root
 5 26.4GB 216GB 190GB Linux LVM lvm
 6 216GB 431GB 215GB Linux LVM lvm
 7 431GB 646GB 215GB Linux LVM lvm
 9 834GB 834GB 524MB ext2 Fedora /boot
10 834GB 835GB 524MB btrfs Btrfs /boot
11 835GB 887GB 52.4GB hfs+ OS X Mountain Lion
12 887GB 941GB 53.7GB hfs+ Apple HFS/HFS+
13 947GB 1000GB 53.7GB hfs+ OS X Mavericks

ubuntu@ubuntu:~$ sudo gdisk /dev/sda
GPT fdisk (gdisk) version 0.8.8

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): p
Disk /dev/sda: 1953525168 sectors, 931.5 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): D850B3B5-4510-42D5-B288-F6615CCCCD21
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 1953525134
Partitions will be aligned on 8-sector boundaries
Total free space is 378410351 sectors (180.4 GiB)

Number Start (sector) End (sector) Size Code Name
   1 40 614439 300.0 MiB EF00 EFI System
   2 614440 1638439 500.0 MiB 8300 Ubuntu /boot
   3 1638440 2662439 500.0 MiB 8300 Ubuntu 14.04 /boot
   4 2662440 51490565 23.3 GiB 8300 Ubuntu root
   5 51490568 422092839 176.7 GiB 8E00 Linux LVM
   6 422092840 841523239 200.0 GiB 8E00 Linux LVM
   7 841523240 1260953639 200.0 GiB 8E00 Linux LVM
   9 1627955240 1628979239 500.0 MiB 8300 Fedora /boot
  10 1628979240 1630003239 500.0 MiB 8300 Btrfs /boot
  11 1630267392 1732667391 48.8 GiB AF00 OS X Mountain Lion
  12 1732929536 1837787135 50.0 GiB AF00 Apple HFS/HFS+
  13 1848668160 1953523711 50.0 GiB AF00 OS X Mavericks

Command (? for help): v

No problems found. 378410351 free sectors (180.4 GiB) available in 7
segments, the largest of which is 367001600 (175.0 GiB) in size.

Command (? for help): q
ubuntu@ubuntu:~$

As you can see, neither tool reports any problem with the partition table -- although the disk does admittedly have a lot of partitions!

Here's the information that the bug report Web form requests:

$ lsb_release -rd
Description: Ubuntu 14.04 LTS
Release: 14.04

$ apt-cache policy ubiquity
ubiquity:
  Installed: 2.18.4
  Candidate: 2.18.4
  Version table:
 *** 2.18.4 0
        500 http://archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status

[Rod Smith (rodsmith)]

I've done some more testing, and it seems that Ubiquity, at least when run in EFI mode on a GPT disk, wants to see a COMPLETELY BLANK disk; if ANY partition is present, this bug occurs, which prevents installation. Needless to say, this is an EXTREMELY serious bug.

[Jean-Baptiste Lallement (jibel)]

Thanks for your report. I can recreate this bug by creating an empty fat32 partition on a disk with a GPT partition table. The backtrace is the same than bug 1306704. I'm marking this report as duplicate.
I also confirm the error box contains question marks instead of a human readable message.

[Rod Smith (rodsmith)]

I agree it's a duplicate. I've done further testing, and FAT16, NTFS, and ext2fs partitions all seem fine; it's only FAT32 that causes the problem.