I have successfully (file created, ubuntu does NOT issue any error messages) created an image from an entire persistent ubuntu live usb.(sdc1) - the file ubuntu1.img is 4.3gb so it is reasonable to believe that the command
/media/images/tst# dd if=/dev/sdc1 of=/media/images/tst/ubuntu1.img
is correctly formatted and made a valid image of usb drive.
So ......i try to put the image onto a newly fat32 formated usb. both the original usb and the new usb have 2 partitions, the first partition on both usbs is ubuntu live. the partition being copied to on the new usb is a little bigger than the original usb partition copied (so size should not be a problem).
dd command to copy image onto usb (i cd to the folder where ubuntu1.img is located)
/media/images/tst# dd if=ubuntu1.img of=/dev/sdc1
this process also displays no errors, after about 20minutes the result is
8388607+1 records in
8388607+1 records out
4294967295 bytes (4.3 GB) copied, 1615.69 s, 2.7 MB/s
BUT ... the usb is useless bios complains about missing GRLDR
i have tried with ubuntu, kali, backtrack, slax, and one or two other linux distros. i have tried with multiple pcs all of which boot from live usb without problem. The only way i have found to copy a linux live usb reliably, is in windows :((
if anyone has successfully used dd to copy a linux live usb (any) distro to an image file, then from same image file to a new usb .........PLEASE share some wisdom - thank you in advance for reading and taking the time to reply