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What are the differences between the following two scenarios?

  • copying the content of a Linux ISO file to a USB drive (with the dd command), then booting from it
  • burning the ISO to CD, then installing from that CD

--UPDATE--

I've installed Ubuntu 12.04 from my USB drive by just using dd command ( https://wiki.archlinux.org/index.php/USB_Installation_Media ) .

Many answer about Unetbootin but I didn't ask "how to create bootable USB". It seems in my scenario, what Unetbootin can do is needless.

  • Is burning the ISO to CD just "copy" data from ISO to CD?
  • Is dd is just copy data from ISO to USB drive?
  • if yes, why you need Unetbootin for usb bootable creating?
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5 Answers 5

You can make bootable usb stick with unetbootin. Afterwards there will be no differece if installed from usb or cdrom.

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Edited based on questions clarification: There's no difference in the two scenarios as long as the target computer can boot from a USB drive.


That seems like a needlessly complex way to go about doing things. Is there any reason in particular that you couldn't load the ISO on the USB drive using something like Unetbootin and boot/install from the USB drive?

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if there is no difference, I wonder what does Unetbootin do? why you don't just copy content of ISO file to your USB? –  HVNSweeting Aug 27 '12 at 17:39
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Unetbootin sets up the USB to be a bootable disk by configuring the master boot record, creating partitions, and a handful of other things. If you just copied the ISO file on to the USB, the computer would have no idea how to boot from it. This same operation is done by your ISO CD burning program in the background. There's some overall information on the process at aaltonen.co/2004/03/01/tip-boot-from-usb-key-addendum –  bobmagoo Aug 27 '12 at 18:04
    
I've install Ubuntu 12.04 to my laptop by using only dd command. It is not like you said that "the computer would have no idea how to boot from it". Because it worked, I'm not sure about things you said about Unetbootin. And IMO, use a built-in command is more easier than install addition program wiki.archlinux.org/index.php/USB_Installation_Media –  HVNSweeting Aug 28 '12 at 13:39
    
this is what I get from UNetbootin homepage: For the Live USB creation mode, UNetbootin downloads and extracts an ISO file to your USB drive, generates an appropriate syslinux config file, and makes your USB drive bootable using syslinux. Thank for that information but what I asked was about differences between using dd and CDRom –  HVNSweeting Aug 28 '12 at 13:45
    
You're getting confused on what the tools do. Both dd and UNetbootin extract ISO files to the target disk/USB. That extract delineation is key. As I said in my first comment, if you just copied the ISO file to the USB/CD, the system wouldn't boot. Using dd and UNetbootin will do that extraction of the ISO contents for you. UNetbootin gives you the ability to acquire ISO's you don't already have, set up a persistent USB drive such that data is preserved across reboots, auto-select the USB drive, and other user-friendly features that make it preferable to some users/situations. –  bobmagoo Aug 28 '12 at 17:23

Yes, there is difference in speed. USB key should be consistently faster in booting. Optical drives may become slower as they age or even be unable to read your media. So, if you have an older system or have multiple systems to install from a single USB/CDROM, USB would be a better choice.

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There isn't any difference in the installed system (nor there could be, since the two methods are based on the same ISO image).

Unetbootin just makes it more convenient for Windows users. Besides, from USB install is faster; given that pretty much any recent machine can boot from USB, it's pretty much the easiest way to go.

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There is no difference, because the end result is the same, the different installation mechanisms are aimed to cover various scenarios of existing hardware, or installation expectations.

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can you provide more about some scenarios that these mechanisms are armed to cover? –  HVNSweeting Aug 28 '12 at 14:05

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