Daily builds now hybrid CD/USB images

Mario Limonciello superm1 at ubuntu.com
Wed Jun 15 21:28:10 UTC 2011

Hi Colin,

On Wed, Jun 15, 2011 at 16:22, Colin Watson <cjwatson at ubuntu.com> wrote:

> As of tomorrow's daily builds, all Oneiric amd64 and i386 CD images on
> cdimage.ubuntu.com can also be written directly to a USB device.  You
> can still use usb-creator if you need to enable persistent storage on
> the USB stick, but if all you need is to install from the stick then
> this simplifies the process.
> There is a small size cost to this feature; part of this is partition
> alignment to 1MB "cylinders" (since the image now has to simultaneously
> look like a CD and a partitioned USB disk), and part of it is a second
> directory tree whose size is roughly proportional to the number of files
> in the image.  On the server CD (and probably the alternate CD too,
> though I haven't measured that), this came out to about 5MB, but as luck
> would have it I found a way to save about the same amount by hardlinking
> some files together, so the size there stays roughly the same.  On the
> desktop CD, unfortunately, we lose about 1MB (although I consider myself
> to have "paid" for this by way of the 2MB or so we gained by switching
> to live-build ...).  If this becomes a problem close to release time,
> then we may be able to shave off a bit at the possible cost of some
> USB-booting compatibility on a few machines by dropping the 1MB
> alignment.  See the recent thread on pkg-libburnia-devel for details.
> I realise that we're behind a number of other major distributions on
> this.  The delay was because (like Debian) we couldn't simply use
> isohybrid because that would break jigdo downloads, so we had to switch
> to xorriso as the CD image generator on these architectures for its new
> JTE support, and by the time all that landed in Debian I didn't really
> want to cram it into 11.04.  See
> http://blog.einval.com/2011/01/07#isohybrid_CDs for the gory details,
> and thanks a lot to Steve, Thomas, and George for their hard work on
> that.
> Please file bugs on https://bugs.launchpad.net/ubuntu-cdimage if this
> change causes the image to stop working on machines where it previously
> worked.
> Cheers,
> --
> Colin Watson                                       [cjwatson at ubuntu.com]
> --
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When written to a USB stick in this fashion, what filesystem is the stick
operating as?  If it's not actually FAT32 (or FAT16 for that matter), I'm
wondering what uEFI firmware will say about it when trying to boot in uEFI

Mario Limonciello
superm1 at ubuntu.com <superm1 at gmail.com>
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