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If I inspect an hybrid ISO with tools like fdisk and gdisk, then looks like hybrid ISO has both the MBR and GPT in order to support both the BIOS and UEFI:

# gdisk -l /dev/sdb
GPT fdisk (gdisk) version 0.8.10

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

Found valid MBR and GPT. Which do you want to use?
 1 - MBR
 2 - GPT
 3 - Create blank GPT

Your answer:

If I inspect the disk with fdisk then it looks broken because inside a larger partition is a smaller one which should be impossible:

# fdisk -l /dev/sdb

Disk /dev/sdb: 7.5 GiB, 8036285952 bytes, 15695871 sectors
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: dos
Disk identifier: 0x4a2bafa7

Device     Boot Start     End Sectors  Size Id Type
/dev/sdb1  *        0 1284095 1284096  627M  0 Empty
/dev/sdb2        8568    9399     832  416K ef EFI (FAT-12/16/32)

#

How such hybrid MBR-GPT setups work?

Martin
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    There is no partition table. It is faked. Don't bother trying to understand it. It doesn't make sense, and isn't an ISO in any case. – mikeserv Feb 05 '16 at 03:40
  • @mikeserv Does this mean that hybrid ISO is a separate boot sector itself like MBR and GPT are and tools like `fdisk` and `gdisk` can not properly handle hybrid ISO boot sectors? – Martin Feb 08 '16 at 21:11

1 Answers1

3

An USB flashdrive on which the hybride iso has been written, cannot be re-partitioned with fdisk or gparted anymore because hybrid partitions (combining ISO partition, GPT and MBR partitions) confuse fdisk and gparted. it will work very well with Linux on BIOS and UEFI system, but yo cannot re-partition it again with fdisk and Gparted because it thinks that the flashdrive has invalid partitions.

If you ever need to re-partition the flash drive again, just do :

dd if=/dev/zero of=/dev/<flash-drive-device-name> bs=1M count=1

After doing this Gparted will regard you flash drive as completely empty and will offer to create a new MS-DOS partition table.

GAD3R
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