ISO on USB has duplicate partition entry

General Discussion
1

Hi, I know this has been discussed but i’m not able to find the thread here. What is the explanation again? Is that an artifact of the iso9660 filesystem? -When you write the .iso to a flash drive, it has two ‘Qubes…’ partitions with the exact same name. And an EFI partition.

thanks!

2

Could you provide the way you write an .iso to the drive as well as screenshots of commands/GUI tools showing your situation?

3

Sure, using Linux

> dd if=Qubes-R4.2.4-x86_64.iso bs=10M conv=fsync status=progress of=/dev/sdi

> lsblk -f /dev/sdi
NAME   FSTYPE  FSVER            LABEL               UUID                                 FSAVAIL FSUSE% MOUNTPOINTS
sdi    iso9660 Joliet Extension QUBES-R4-2-4-X86-64 2025-02-17-04-55-08-00                              
├─sdi1 iso9660 Joliet Extension QUBES-R4-2-4-X86-64 2025-02-17-04-55-08-00                              
├─sdi2 vfat    FAT12            ANACONDA            1296-E980                                           
└─sdi3 iso9660 Joliet Extension QUBES-R4-2-4-X86-64

> fdisk -l /dev/sdi
GPT PMBR size mismatch (14191415 != 30031871) will be corrected by write.
The backup GPT table is not on the end of the device.
Disk /dev/sdi: 14.32 GiB, 15376318464 bytes, 30031872 sectors
Disk model: Ultra           
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 0C1004A4-4BBD-44DA-9BC4-BC40BA548C12

Device        Start      End  Sectors  Size Type
/dev/sdi1        64 14180923 14180860  6.8G Microsoft basic data
/dev/sdi2  14180924 14190751     9828  4.8M EFI System
/dev/sdi3  14190752 14191351      600  300K Microsoft basic data

When you insert the USB you see two hard drives to mount. Only the first works.

4

IIUC the 300 KiB partition containing only zero bytes is padding automatically created by xorrisofs to accommodate optical disk writers in track-at-once mode somehow. It actually has the GPT partition label Gap1, I don’t know why lsblk doesn’t show it properly.

$ sudo losetup --find --show --read-only --partscan Qubes-R4.2.4-x86_64.iso
/dev/loop0

$ readlink -f /dev/disk/by-partlabel/Gap1
/dev/loop0p3

$ sudo hexdump -C /dev/disk/by-partlabel/Gap1
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
0004b000
1 Like
5

Ok thanks. Apparently KDE Plasma’s disk notifier GUI uses the same mechanism as lsblk. But fdisk --list-details shows it correctly.

fdisk --list-details /dev/sdi
GPT PMBR size mismatch (14191415 != 120176639) will be corrected by write.
The backup GPT table is not on the end of the device.
Disk /dev/sdi: 57.3 GiB, 61530439680 bytes, 120176640 sectors
Disk model: USB Flash Drive 
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 0C1004A4-4BBD-44DA-9BC4-BC40BA548C12
First usable LBA: 64
Last usable LBA: 14191352
Alternative LBA: 14191415
Partition entries starting LBA: 2
Allocated partition entries: 248
Partition entries ending LBA: 63

Device        Start      End  Sectors Type-UUID                            UUID                                 Name      Attrs
/dev/sdi1        64 14180923 14180860 EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 0C1004A4-4BBD-44DA-9BC5-BC40BA548C12 ISO9660   RequiredPartition LegacyBIOSBootable GUID:60
/dev/sdi2  14180924 14190751     9828 C12A7328-F81F-11D2-BA4B-00A0C93EC93B 0C1004A4-4BBD-44DA-9BC6-BC40BA548C12 Appended2 
/dev/sdi3  14190752 14191351      600 EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 0C1004A4-4BBD-44DA-9BC7-BC40BA548C12 Gap1      RequiredPartition GUID:60