Re: Failure to boot from external USB thumb drive - telling 'bootable' and 'hybrid'

Hi Paul, all!


On 06.04.21 14:08, Paul Bolle wrote:
> Joerg Bruehe schreef op di 06-04-2021 om 13:37 [+0200]:
>> Sorry, I don't know a way to tell whether an ISO image is a hybrid one.
>> I'm still searching for one.
> 
> file? As in:
> 
> $ file Fedora-Workstation-Live-x86_64-32-1.6.iso
> Fedora-Workstation-Live-x86_64-32-1.6.iso: ISO 9660 CD-ROM filesystem data
> (DOS/MBR boot sector) 'Fedora-WS-Live-32-1-6' (bootable)
> 
> The "(DOS/MBR boot sector)" stuff makes it a hybrid, doesn't it?

I hadn't known that, it sounds extremely plausible.


Looking at three different ISO images, I get:

- for a non-bootable ISO image:
$ file VBoxGuestAdditions.iso
VBoxGuestAdditions.iso: ISO 9660 CD-ROM filesystem data 
'VBOXADDITIONS_5.2.42_137960'

- for a bootable CD ISO image for firmware updates:
$ file Barracuda12-ALL-CC49.iso
Barracuda12-ALL-CC49.iso: ISO 9660 CD-ROM filesystem data 'SEAGATE' 
(bootable)

- for a bootable Knoppix ISO image:
$ file KNOPPIX_V8.6.1-2019-10-14-DE.iso
KNOPPIX_V8.6.1-2019-10-14-DE.iso: DOS/MBR boot sector; partition 2 : 
ID=0xef, start-CHS (0x3e4,0,1), end-CHS (0x3e7,55,39), startsector 
9035712, 30720 sectors; partition 3 : ID=0x83, start-CHS (0x3e7,55,40), 
end-CHS (0x3e8,41,41), startsector 9066432, 8192 sectors

Yes, this last one really has a partition table:
$ fdisk -l KNOPPIX_V8.6.1-2019-10-14-DE.iso
Festplatte KNOPPIX_V8.6.1-2019-10-14-DE.iso: 4,3 GiB, 4646207488 Bytes, 
9074624 Sektoren
Einheiten: Sektoren von 1 * 512 = 512 Bytes
Sektorgröße (logisch/physikalisch): 512 Bytes / 512 Bytes
E/A-Größe (minimal/optimal): 512 Bytes / 512 Bytes
Festplattenbezeichnungstyp: dos
Festplattenbezeichner: 0x746eeb45

Gerät                             Boot  Anfang    Ende Sektoren Größe Kn Typ
KNOPPIX_V8.6.1-2019-10-14-DE.iso1 *         64 9035711  9035648  4,3G  0 
Leer
KNOPPIX_V8.6.1-2019-10-14-DE.iso2      9035712 9066431    30720   15M ef 
EFI (FAT-12/16/32)
KNOPPIX_V8.6.1-2019-10-14-DE.iso3      9066432 9074623     8192    4M 83 
Linux

And yes, even with the partition table it can be mounted as a file system:
$ sudo mount -o loop,ro KNOPPIX_V8.6.1-2019-10-14-DE.iso /mnt
$ ls -al /mnt/
insgesamt 50
dr-xr-xr-x  1 root root  2048 Aug 17  2019 .
drwxr-xr-x 33 root root  4096 Mär 25 09:51 ..
-r-xr-xr-x  1 root root    54 Jun 17  2001 autorun.bat
-r-xr-xr-x  1 root root    45 Feb 23  2003 autorun.inf
-r-xr-xr-x  1 root root   967 Mai  1  2004 autorun.pif
dr-xr-xr-x  1 root root  2048 Jan 24  2017 boot
-r--r--r--  1 root root 32606 Feb 22  2006 cdrom.ico
dr-xr-xr-x  1 root root  2048 Mai 31  2013 efi
-r--r--r--  1 root root  1709 Aug  8  2019 index.html
dr-xr-xr-x  1 root root  4096 Nov 22  2019 KNOPPIX

The above output is from Kubuntu 18.04 LTS, German locale. Its 'file' 
command seems to generate a different format from Paul's, but the text 
is sufficiently close.


Coming back to the original issue:
To me, it sounds wise to check the ISO image using 'file' and 'fdisk'.

If 'file' reports "DOS/MBR boot sector", I would suspect a USB stick 
boot issue like BIOS limitation or USB bus restrictions.

If it doesn't, my guess is that it isn't a hybrid image and so it isn't 
bootable from a stick, but one of the "usb-creator-*" packages might 
help to create one.


Again: HTH and Good Luck!

Jörg

-- 
Joerg Bruehe  - persoenliche Aeusserung / speaking only for himself
mailto:[email protected]

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