Friday, 23 January 2015

Re: Creating Ubuntu USB sticks

On 1/23/15 2:09 PM, Colin Ian King wrote:
> On 23/01/15 18:29, Rodney Dawes wrote:
>> On Thu, 2015-01-22 at 16:22 +0100, Stefan Bader wrote:
>>> On 22.01.2015 15:23, Rodney Dawes wrote:
>>>> I've been trying to create one recently, under 14.04 running the
>>>> lts-utopic kernel. It seems the old problem of flushing is back. When I
>>>> run "dd if=ubuntu-14.04.1-amd64.iso of=/dev/sdg bs=4096" it exits almost
>>>> immediately, and then the LED on the USB spends the next several minutes
>>> That is the expected behaviour with that incantation. If you added a
>>> "oflag=sync" dd should return only after write has finished. In your case you
>>> use cached writes.
>> Even with oflag=sync, I still get an unbootable USB stick. Now it is
>> showing the following messages when trying to boot:
> I'll be tempted to write all zeros to it and see if you get all zeros
> when you read it back. Sounds like the media is unreliable.
>
> e.g
>
> dd if=/dev/zero of=/dev/sdg oflag=sync
> sum /dev/sdg
>
>
Or the kernel is misreading the device and hence, writing to it
incorrectly and bailing on odd error that isn't in the error handling
routines.

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