Package: os-prober Version: 1.71 Also reproducible in os-prober 1.65
https://anonscm.debian.org/cgit/d-i/os-prober.git/tree/os-probes/mounted/x86/05efi#n42..n45 Disk has regular MBR table. It has Windows 7 and Ubuntu installed on different partitions. Os-prober doesn't detect EFI partition on MBR table because "udevadm info" returns "dos" partition scheme instead of expected "msdos". $ udevadm info /dev/sda1 | grep dos E: ID_PART_ENTRY_SCHEME=dos E: ID_PART_TABLE_TYPE=dos $ fdisk -lu /dev/sda | grep -B1 -A1 ef Device Boot Start End Blocks Id System /dev/sda1 * 2048 616447 307200 ef EFI (FAT-12/16/32) /dev/sda2 616448 128134439 63758996 7 HPFS/NTFS/exFAT Fixing conditions below resolves the issue: - \( "$ID_PART_ENTRY_SCHEME" != gpt -a "$ID_PART_ENTRY_SCHEME" != msdos \) -o \ + \( "$ID_PART_ENTRY_SCHEME" != gpt -a "$ID_PART_ENTRY_SCHEME" != dos \) -o \ \( "$ID_PART_ENTRY_SCHEME" = gpt -a "$ID_PART_ENTRY_TYPE" != c12a7328-f81f-11d2-ba4b-00a0c93ec93b \) -o \ - \( "$ID_PART_ENTRY_SCHEME" = msdos -a "$ID_PART_ENTRY_TYPE" != 0xef \) ]; then + \( "$ID_PART_ENTRY_SCHEME" = dos -a "$ID_PART_ENTRY_TYPE" != 0xef \) ]; then Probably this bug relates to udevinfo replacement (https://lists.debian.org/debian-user/2010/07/msg01134.html). P.S. Cross-posting report in ubuntu launchpad https://bugs.launchpad.net/ubuntu/+source/os-prober/+bug/1553678