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Interesting! How did you go about falling back to an older version if the update was bad? Is there a nice way to do this automatically? Say I update to a really

by padelt 10y ago

Interesting! How did you go about falling back to an older version if the update was bad? Is there a nice way to do this automatically? Say I update to a really botched version with the kernel panicing before it reaches userland. Does this need manual intervention?

mpasinski 10y ago
disclaimer: I work for Mender It is possible to make rollback fully automatic. In order to do so you need some integration with bootloader. It needs to be configured so that it can roll back to the previously working partition if update is broken. What is more, you can add some user space runtime checks that can verify the update and if those are not passing (updated image is broken) you can rollback to the previous one as well.
- padelt 10y ago
  (Way) back when I was working with OpenEmbedded/Ångström I dreamt up sth like this: make uboot/whatever set up a HW watchdog that is retriggered once from kernel mode and then in the userspace as ususal. The daunting task would've been to implement the (platform specific) watchdog in the bootloader. Looking now, there is support for at least some platforms - nice! Good luck with Mender - I'm sure you are badly needed!
- dividuum 10y ago
  As someone that also implemented A/B booting for the Pi: I wonder how you roll back fully automated? I read a bit of the code but wasn't able to find that. Or is that already handled by u-boot? In my case, the first thing I do once an unverified version boots is to switch back to the other partition (so the known good version is active during the next boot), then run a detached reboot process that forces a reboot in 5 minutes. Once the system is up and it verified that everything is ok, it commits the next version (by switching back to the partition that booted and marking it as confirmed) so it is now active by default. Finally it kills the still running 'reboot' process. As far as I understand your update process: You download a complete new version for every update and are able to stream that directly to the new partition? Is there any way to do delta updates? In my experience, most of the disk content is unchanged, unless you do major updates. In my case I download the new version using zsync, verify the downloaded/updated `install.zip` (which is kept on the volatile data partition), then extract that to the new partition. I make sure that `install.zip` is created in a way that it is rsyncable, so updates are pretty small that way. Of course you lose the streaming feature, unless you modify zsync somehow to support that.
  - eystein 10y ago
    I work on Mender, so I can tell you how automated rollback works there. The update is written to the inactive rootfs partition, uboot is configured to boot from it and the device is rebooted. Using the bootcount feature of uboot it is possible to roll back automatically if booting fails. Once the mender daemon comes up it will try to report the success of the deployment to the server. If this fails it will also roll back. Only after successfully reporting the success to the server Mender will "commit" the update, meaning configuring uboot to persistently boot from this updated partition. Mender already does compression, but you are right that there are optimizations that can be made for application updates, e.g. delta or other types of updates. We are planning to implement this as well. The first priority for Mender is to make it robust, i.e. make sure the update is atomic and that you can always roll back.
    - dividuum 10y ago
      > Using the bootcount feature of uboot it is possible to roll back automatically if booting fails. I see. Thanks for the info. I suspected that u-boot does have support for that, but I wasn't sure. > Once the mender daemon comes up it will try to report the success of the deployment to the server. If this fails it will also roll back. Is there any deadline at all for that? I explicitly spawn a reboot command that ensures that even if everything gets stuck (in software, not in hardware) for whatever reason, the system falls back to the previous version (unless the reboot command gets killed too, in which case a manual restart is required). Any thoughts on that?
      - ralphmender 10y ago
        This is a valid point. If booting just hangs after the bootloader but before the Mender daemon comes up is actually quite tricky to manage. We have looked into hardware watchdog for this, but it is in the gray-zone of what an updater should be involved in. This is actually a more generic problem - maybe it hangs even when you did not deploy an update. There is varying support for hardware watchdogs across boards as well, unfortunately. Most of the time it will not just hang, maybe it will crash or kernel panic and in those cases Mender will rollback. But the indefinite-hanging case is quite tricky and not yet handled. Would be open to ideas here.

by padelt 10y ago

mpasinski 10y ago

disclaimer: I work for Mender It is possible to make rollback fully automatic. In order to do so you need some integration with bootloader. It needs to be configured so that it can roll back to the previously working partition if update is broken. What is more, you can add some user space runtime checks that can verify the update and if those are not passing (updated image is broken) you can rollback to the previous one as well.

padelt 10y ago
(Way) back when I was working with OpenEmbedded/Ångström I dreamt up sth like this: make uboot/whatever set up a HW watchdog that is retriggered once from kernel mode and then in the userspace as ususal. The daunting task would've been to implement the (platform specific) watchdog in the bootloader. Looking now, there is support for at least some platforms - nice! Good luck with Mender - I'm sure you are badly needed!
dividuum 10y ago
As someone that also implemented A/B booting for the Pi: I wonder how you roll back fully automated? I read a bit of the code but wasn't able to find that. Or is that already handled by u-boot? In my case, the first thing I do once an unverified version boots is to switch back to the other partition (so the known good version is active during the next boot), then run a detached reboot process that forces a reboot in 5 minutes. Once the system is up and it verified that everything is ok, it commits the next version (by switching back to the partition that booted and marking it as confirmed) so it is now active by default. Finally it kills the still running 'reboot' process. As far as I understand your update process: You download a complete new version for every update and are able to stream that directly to the new partition? Is there any way to do delta updates? In my experience, most of the disk content is unchanged, unless you do major updates. In my case I download the new version using zsync, verify the downloaded/updated `install.zip` (which is kept on the volatile data partition), then extract that to the new partition. I make sure that `install.zip` is created in a way that it is rsyncable, so updates are pretty small that way. Of course you lose the streaming feature, unless you modify zsync somehow to support that.
- eystein 10y ago
  I work on Mender, so I can tell you how automated rollback works there. The update is written to the inactive rootfs partition, uboot is configured to boot from it and the device is rebooted. Using the bootcount feature of uboot it is possible to roll back automatically if booting fails. Once the mender daemon comes up it will try to report the success of the deployment to the server. If this fails it will also roll back. Only after successfully reporting the success to the server Mender will "commit" the update, meaning configuring uboot to persistently boot from this updated partition. Mender already does compression, but you are right that there are optimizations that can be made for application updates, e.g. delta or other types of updates. We are planning to implement this as well. The first priority for Mender is to make it robust, i.e. make sure the update is atomic and that you can always roll back.
  - dividuum 10y ago
    > Using the bootcount feature of uboot it is possible to roll back automatically if booting fails. I see. Thanks for the info. I suspected that u-boot does have support for that, but I wasn't sure. > Once the mender daemon comes up it will try to report the success of the deployment to the server. If this fails it will also roll back. Is there any deadline at all for that? I explicitly spawn a reboot command that ensures that even if everything gets stuck (in software, not in hardware) for whatever reason, the system falls back to the previous version (unless the reboot command gets killed too, in which case a manual restart is required). Any thoughts on that?
    - ralphmender 10y ago
      This is a valid point. If booting just hangs after the bootloader but before the Mender daemon comes up is actually quite tricky to manage. We have looked into hardware watchdog for this, but it is in the gray-zone of what an updater should be involved in. This is actually a more generic problem - maybe it hangs even when you did not deploy an update. There is varying support for hardware watchdogs across boards as well, unfortunately. Most of the time it will not just hang, maybe it will crash or kernel panic and in those cases Mender will rollback. But the indefinite-hanging case is quite tricky and not yet handled. Would be open to ideas here.