Saturday, 24 January 2015

Re: Creating Ubuntu USB sticks

On Fri, Jan 23, 2015 at 01:29:20PM -0500, 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:
>
> CHS: Error 0101 reading sector 2004736 (978/56/1)
> EDD: Error 0100 reading sector 2004736
> Unknown keyword in configuration file: KK.TR;1PX$
> Unknown keyword in configuration file: r
> Unknown keyword in configuration file: kk.trt
> No DEFAULT or UI configuration directive found!
> boot:

I had a lot of pain with =sync recently (as suggested by the FreeBSD
docs to create bootable media). It seems to me that what people should
suggest are "fsync" and/or "fdatasync", at least according to the man
page:

sync pad every input block with NULs to ibs-size; when used with
block or unblock, pad with spaces rather than NULs
[...]
fdatasync
physically write output file data before finishing
fsync likewise, but also write metadata

Kind regards
Philipp Kern

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