Re: [PATCH 2/3] common: machine_id: introduce machine id generation and pass id on

[Bastian Krause <bst@pengutronix.de>]

On 7/17/19 12:31 PM, Ahmad Fatoum wrote:
> 
> 
> On 17/7/19 12:02, Roland Hieber wrote:
>> On Tue, Jul 16, 2019 at 12:58:36PM +0200, Bastian Krause wrote:
>>> By default systemd generates a machine id on first boot and tries to
>>> persist it (see `man machine-id`). When the root file system is read-only
>>> systemd cannot persist the machine id. In case multiple redundant slots
>>> are used the machine id will vary. When not handled explicitly the
>>> machine id will also change during updates.
>>>
>>> It is possible to pass a machine id to the kernel which will be used by
>>> systemd (systemd.machine_id=).
>>>
>>> This adds functionality to pass device-specific information that will be
>>> hashed to generate a persistent unique machine id. The machine id will
>>> be finally added to the kernel parameters via the
>>> linux.bootargs.machine_id global variable.
>>>
>>> Note: if multiple sources provide hashable device-specific information
>>> (via machine_id_set_hashable()) the information provided by the last call
>>> prior to the late initcall set_machine_id() is used to generate the
>>> machine id from. Thus when updating barebox the machine id might change.
>>
>> I would also add this paragraph to the kconfig help text, so it is more
>> visible for users.
> 
> Maybe add a priority parameter like we do with e.g. reset reason?
> That way we can have a base machine-id in the OTP, but board code can
> override it with e.g. an EEPROM value which is given higher priority.

Hm, that makes things complicated. At the end everybody will have their
own high priority call like..

  machine_id_set_hashable(my_board_specific_info, len, 99);

.. to have a machine id that persists such an update scenario? That does
not sound too good to me..

Any opinions on this?

Bastian

-- 
Pengutronix e.K.
Industrial Linux Solutions
http://www.pengutronix.de/
Peiner Str. 6-8, 31137 Hildesheim, Germany
Amtsgericht Hildesheim, HRA 2686

_______________________________________________
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox