RFC: handling kernel cmdline options in gadget snaps

Paul Larson paul.larson at canonical.com
Mon Jul 6 17:58:22 UTC 2015

nevermind, I somehow missed the part where you were trying to say you
wanted to do this *without* having a separate gadget snap :)

On Mon, Jul 6, 2015 at 12:56 PM, Paul Larson <paul.larson at canonical.com>

> Couldn't we just put it in uEnv.txt and have uboot read it from there like
> we do with uenvcmd and bootpart?
> On Mon, Jul 6, 2015 at 10:56 AM, Oliver Grawert <ogra at ubuntu.com> wrote:
>> hi,
>> we are currently facing a problem of having hardcoded console= options
>> on the kernel commandline ...
>> (grub images currently default to: "console=ttyS0 console=tty0" (the
>> first option applies to kernel while the second sets the output console
>> for userspace) while u-boot images default to whatever serial console
>> device an embedded board uses)
>> to change your console= option you theoretically would have to build
>> your own gadget snap just for that one option modified ...
>> ... or we would have one gadget snap per possible option in the store so
>> the user can pick the "amd64-serial-console.snap" for his serial snappy
>> project ... this would indeed make us end up with tons of identical
>> snaps that only have a single option changed ...
>> i would like us to find a way how we can set the console option
>> dynamically at image creation time for this case ...
>> technically grub based images do not need a console= option set by
>> default (they will resort to tty0 which is fine for VM as well as for
>> real hardware) but you might want to use some x86 based embedded board
>> that only offers serial ports for debugging or logging in ... u-boot
>> images should default to whatever the HW requires. but while i do not
>> expect us to use a beaglebone for any graphical images (since it is
>> simply not designed for this), i expect that RPi2 users will likely want
>> to be able to use graphical consoles (and a boot splash etc) in case
>> they run some desktop or some media playback tool on their snappy
>> install.
>> while we technically could use "snappy config" to adjust this, this is
>> practically only possible after you booted ... so you would have to boot
>> blind to an invisible console to change the default setting ...
>> the only sane option i see is to add some option to ubuntu-device-flash
>> so this value can be modified at image creation time before the first
>> boot ... but this seems to be unwanted either (u-d-f already has a
>> plethora of options and slowly gets crowded with them)
>> since i don't see an easy path out of this dilemma, i was wondering if
>> anyone else has any good idea what we can do here ...
>> ciao
>>         oli
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