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i extracted a ubuntu 12.04 amd64 in usb by startup disk creator and the original image is deleted when i install ubuntu 12.04 from usb now how can i remake iso image from usb without re download iso?

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How did you extract it? – Mitch Jun 1 '12 at 14:41
i did not extract it but i use start up disk creator please help i can't re download my internet speed is not fast. – Liang Lee Jun 1 '12 at 14:43

You can use dd for this. Make sure that your USB device is recognized by the system as /dev/sdb. You should make sure that this is the case before executing any of the commands below, because if you get the device name wrong, the second command below will end up overwriting the wrong device and destroying your data.

To make an image from your existing USB setup and write it to the file usb-image.iso:

Just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command below.

sudo dd if=/dev/sdb of=usb-image.iso
Again it is EXTREMELY IMPORTANT that you make sure you're using the correct device name before executing the command above. Otherwise you run the risk of clobbering the data on some other disk device that may be critical to your system.

Source: Ubuntu Forums

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Did this work for you? – Mitch Jun 9 '12 at 7:02

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