Hi, [email protected] wrote: > > > The drive isn't formatted
Greg Wooledge wrote: > > What ? I assume that the drive was not explicitly partitioned after it was used as storage device for an ISO 9660 image. The ISO image possibly brought its own partitioning, e.g. if it is a Debian installation ISO. What [email protected] saw was the UUID of that ISO 9660 filesystem. Depending on the way how the next partitioning of the device is made, it might be that the ISO UUID survives on the overall device (e.g. /dev/sdc) but probably not in the newly made partitions. The UUID of ISO 9660 is taken from a field in 2048-bytes block 16 of the storage device (that's 512-bytes blocks 64 to 67). If these blocks don't get overwritten by the next partitioning, then the ISO UUID might still get shown. [email protected] wrote: > My knowledge of ISO 9660 is cursory but note the first sentence > in https://en.wikipedia.org/wiki/Optical_disk_image , > "... disk image ... written to an optical disk, disk sector by disc sector > ...". > Not directly comparable to ext4. I don't find that statement in the wikipedia page. It begins by: "A disk image is a snapshot of a storage device's content – typically stored in a file on another storage device." The term "disk image" is not restricted to optical media and not to ISO 9660 filesystems. If you make an image of a single ext4 filesystem, then this is most probably a partition image. I.e. it does not cover the whole disk. If you put it on the base storage device (e.g. /dev/sdc, not /dev/sdc1) then there will be no partitioning on that device any more. The filesystem will be mountable by the base device. Ancient danger: The partition image might contain parts of the old partition table if it stems from a "logical" MBR partition. See https://en.wikipedia.org/wiki/Extended_boot_record . The normal use case is to make a disk image of a storage device which holds a partition table and one or more filesystems in the partitions. If you put this image onto another disk then this disk will inherit the partition table, the partitions, and their content. The new disk needs to be at least as large as the old one, of course. A GPT partition table will need to get its backup header block to the end of the storage medium. Have a nice day :) Thomas
