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hybrid ISO

Since 0.5 up to 0.10.2, every published Tails ISO image has been a hybrid one:

  • it can be burnt to a DVD;
  • it also contains a full disk image (including partition table) and can thus be copied (using dd) to a USB stick; the USB stick's content is lost in the operation.

Then, we stopped hybrid'ing the ISO images we publish, and started again in Tails 1.3.

Nowadays, we pass the -h 255 -s 63 options to isohybrid, as advised by the syslinux community for images between 1 GiB and 4 (?) GiB.

Archives

What follows comes from the Tails 0.10 days.

Successful tests:

  • boot the resulting test.iso as a normal optical drive in VirtualBox

  • boot the resulting test.iso as a KVM hard disk

  • convert the resulting test.iso, posing as a HDD image, into the native VirtualBox disk format, using VBoxManage convertfromraw -format VDI test.iso test.vdi, then boot the resulting test.vdi disk image in VirtualBox

  • dd the hybrid test.iso to a USB stick and boot it on a USB-boot-enabled computer.

Notes:

  • the partition number may need to be 4, in order to be compatible with the BIOSes supporting only USB-Zip.

  • the partition type may need to be 1c, i.e. hidden FAT32 LBA.

  • boot failures were experienced when testing without the -entry 4 -type 1c options.

Conclusion: this is a nice way to get bootable USB images for almost free.