I would like to use the dd command to make a bootable flash drive, but for that I need to know what the correct block size is. I know that I can just boot the ISO in a VM and run parted or fdisk to obtain it, but I would like to know if it's possible to get the block size from the file directly. I've tried looking at it with both parted and fdisk, both mounted and unmounted as a loop device, but I just get the logical block size of the drive where the ISO is located, not the block size of the data in the ISO.


You can use software like cdrecord, isoinfo and search for lines like:

Current Secsize: 2048


Logical block size is: 2048

but why you do not try w/o block size in dd command?

  • 1
    Thanks, isoinfo works. To answer your question, not specifying the block size in dd can lead to problems, like the live usb hanging before reaching the desktop environment. – RayinMay Apr 22 at 21:29

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