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I would like to create a bootable Linux ISO on a USB drive under Debian 9. I found that the ISO is only bootable if it has been written to the disk /dev/XdY. If the ISO is written to a specific partition, e.g. /dev/sdd1, then it is not bootable. What is the technical reason behind this?

It works after writing the ISO to a partition and deleting the partition afterwards using Gnome-Disk, this does not delete the file, but makes the disk bootable.

  • If you're using BIOS+MBR, what did you get if mark that partition as the only boot-able? I believe standard MS-DOS MBR code will chain boot your boot-able partition. – 炸鱼薯条德里克 Sep 17 '18 at 2:11
  • I used sudo dd if=/home/<Windows 10 ISO> of=/dev/sdX to write the ISO to the USB stick, for some reason, the option Gnome-Disk >> Edit partition >> Bootable is greyed out. – david Sep 19 '18 at 18:50
5
  • BIOS machines boot disks.
  • UEFI machines boot the UEFI partition

So neither of those boot just any partition.

If you're looking to have a bootable ISO booting from a partition, you can add the ISO file to /etc/grub.d/40_custom and then grub will "boot" the ISO for you.

E.G. for gparted on my machine where /opt lives in hd2,gpt2

menuentry "GParted Live ISO" {
  set ISOFile="/opt/Live-ISOs/gparted-live-0.31.0-1-amd64.iso"
  loopback loop (hd2,gpt2)$ISOFile
  linuxefi (loop)/live/vmlinuz boot=live components config findiso=$ISOFile ip=frommedia toram=filesystem.squashfs union=overlay username=user
  initrdefi (loop)/live/initrd.img
}
  • 2
    nice idea using grub for the ISO. – Rui F Ribeiro Sep 16 '18 at 19:27
  • May I ask why linuxefi and initrdefi ? I've only done this without efi. – 炸鱼薯条德里克 Sep 17 '18 at 2:08
  • Because my machine is an UEFI machine and I didn't even try the originals. Ping me in chat if you want me to try @神秘德里克 – Fabby Sep 17 '18 at 10:05
  • 1.) What is the technical reason that deleting a partition actually makes an ISO/drive bootable? 2.) I need to install Windows 10 on my old ThinkPad R60 and copied the ISO onto a USB stick from Debian 9, but it does not seem to be recognized as bootable by the laptop. What am I doing wrong? – david Sep 19 '18 at 16:04
  • 1
    That solves the question! Thx – david Sep 20 '18 at 19:57

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