[Dev] [RFC] Tizen system rollback

Carsten Haitzler c.haitzler at samsung.com
Tue Dec 3 02:41:00 GMT 2013

On 12/02/2013 08:32 PM, 함명주 wrote:
>> On Fri, 29 Nov 2013 17:07:18 +0200 Aliaksei Katovich <a.katovich at samsung.com>
>> said:
>>> hi all;
>>> 	I would like to bring to your attention Tizen system rollback feature.
>>> 	The idea is to provide possibility to roll back Tizen based system to
>>> 	one of several known working configurations. Most obvious use-cases
>>> are:
>>> 	* system update or upgrade failed;
>>> 	* there are regressions introduced by system update;
>>> 	* User does not like features added by system update;
>>> 	* User wants to restore device to first time configuration;
>>> 	* User wants to restore device to factory defaults.
>>> 	Proposed architecture is based on device-mapper thin-provisioning
>>> 	capabilities. Please find more details in attached document.
>>> 	Before starting actual implementation of this feature I would like to
>>> 	hear your opinion about presented architecture and the idea in
>>> general.
>>> Thanks,
>>> Aliaksei
>> for updates rendering things unbootable (kernel or low level system) what if an
>> update renders the os unable to even boot? kernel doesn't even work? shouldn't
>> we have a secondary rescue-os install with a "never updated kernel + miniature
>> userspace", which is only JUST big enough to boot, prompt the user that
>> something "bad" happened, maybe ask if they which to go back to stable, factory
>> or initial, then do the rollback, reboot and continue booting normally?
> If you are concerned with a corrupted bootloader. I don't think this feature
> will be able to help you. If it is restricted as low as kernel, it may help.

no - i'm assume bootloader is never touched. i am assuming a kernel WILL 
need updates and thus a "bad kernel update" or for that matter any low 
level system init breaks can render a device unbootable. the user should 
not be forced to go find a pc, download software for it etc. so they can 
reflash to a working device. the device should be able to recover on its 
own "in the field" (no network needed).

> In case of a corrupted 2nd bootloader, it heavily depends on BSP,
> which is not specified by Tizen. For M0s, we have prepared dual bootloader
> for such cases (as some PCs do have dual BIOS) although I don't think
> they are activated with older version. I didn't check whether this feature is
> activated with which version.
> However, there is an incoming requirement, "Safe Mode" and this feature
> might need to be connected with "Safe Mode" somehow.
> Cheers,
> MyungJoo.
>> this would require the real OS to somehow indicate it has booted successfully
>> in a way that stays around in memory - eg some fixed memory region to store a
>> signature with a counter. bootloader needs to know about this memory region and
>> check signature on reboot as well as init the memory to some default known
>> state. if the boot fails to set this memory to "all ok" any re-boot through the
>> bootloader would switch to booting the rescue os.
>> this would allow the same rollback mechanism to be used everywhere with only
>> some minimal support from the bootloader (to know when to automatically switch
>> to the rescue os).
>> btrfs also comes with performance characteristics that may or may not be
>> desirable. there is also tux3 i think that does snapshots (and thus rollbacks).
>> devicemapper seems at a first glance the best option as it works below the fs
>> level thus keeping the choice of fs still open, but it may have performance
>> affects that could range from minimal to severe.
>> -- 
>> Carsten Haitzler (The Rasterman) <tizen at rasterman.com>
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