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So far Ubuntu (and derivatives) has been delivering ISO images to be burned onto optical media. Then there's a tool (usb-creator) to "burn" those ISOs onto USB drives. I could be wrong, but I think that nowadays the majority of users don't use optical media to install Ubuntu (as well as other OSs) also because optical drives are not any more standard.

A "USB image" is usually "burnt" with a standard dd which is readily available within whatever OS you already have. While if you are not coming from Ubuntu it's likely your conversion tool is different from Ubuntu's and it won't work flawlessly.

What is the advantage for Ubuntu to keep the ISO instead of a "dd-able" image?

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Maybe a duplicate? askubuntu.com/questions/150069/… – sege23 Jan 29 at 8:01
3  
the current iso is dd-able and has been for a couple of years now – mchid Jan 29 at 8:01
    
Of the currently available tools on Windows, Unetbootin and Universal USB Installer have been working flawlessly with Ubuntu images for years now. – muru Jan 29 at 8:28
1  
Because ISO images can easily be burned to a CD, DVD, or USB thumb drive, whereas providing a USB drive installation format wouldn't work on a CD/DVD. – dr01 Jan 29 at 9:35
up vote 11 down vote accepted

The current iso image is ddable and the images have been ddable for quite some time now as far as I know.

sudo dd if=./ubuntu.iso of=/dev/sdx bs=16M

Where ./ubuntu.iso is the path to the actual file and /dev/sdx is the target USB drive.

Alternatively, you can use cat instead of dd which is arguably faster like so:

sudo -i
cat ./ubuntu.iso > /dev/sdx
exit

Again, ./ubuntu.iso represents the full path to the actual iso file and /dev/sdx is the actual USB device.

Even if the image were not ddable, it would simply take a couple of syslinux commands to convert the image to ddable form.


Hypothetically, if the Ubuntu iso images were not ddable, you would just have to run the following commands:

sudo apt-get install syslinux
isohybrid ./ubuntu.iso --entry 4 --type 0x1c
dd if=./ubuntu.iso of=/dev/sdx bs=16M

Again, where ./ubuntu.iso is the path to the actual iso file and /dev/sdx is the actual USB device.

source

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2  
Another nice way of doing it is with sudo -i and pv /path/to/image.iso >/dev/sdX for the fancy progress bar. – kos Jan 29 at 8:37
1  
@kos newer versions of dd also have a progress bar but I don't think we have it yet wiki.archlinux.org/index.php/core_utilities#dd – mchid Jan 29 at 8:51
    
No, but we should be almost there, on Vivid the latest available version of coreutils is 8.23 and the progress bar for dd has been introduced in coreutils 8.24: askubuntu.com/a/715075/380067 – kos Jan 29 at 8:54
    
@mchid I voted to your answer. But ... 1) The link you give is not for Ubuntu but TAILS. 2) The link you provided is available only as an archived page and it's not current. 3) The Official Ubuntu Documentation says otherwise (I linked it in the question). Nonetheless I think you're right, sir. – Uqbar Jan 29 at 10:04
    
It might be relevant to mention that trying to install Ubuntu on the USB media which you just booted the installer from can be tricky. One has to add toram to the boot command line in order to make it work (and that only works if you have at least 2GB of RAM). – kasperd Jan 29 at 12:58

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