ERROR cannot finish core installation, there was a rollback across reboot

[Denis S]

Hello,

I have a custom board where I've installed Ubuntu Core with a self-made kernel snap and a gadget snap. 
It seems that it works but the core snap doesn't get updated. I've changed ubuntu-image parameters to switch from stable channel to edge channel.
The problem persists but at least there is a log info at the end of "snap change" command in the "edge" version of the core snap. 

RaspberyPi3 can switch core snaps without problems (using standard image with 4.4 xenial kernel). It hangs "Doing" setup security profiles (phase 2) but after the planned reboot it shows that every stage was successful, even phase 2. My platforms hangs on the same stage but after reboot I see a rollback. Hang doesn't mean at all. The symbol [/] keeps spinning but never finishes before 10 min reboot timeout. 

My kernel is:
$ uname -a
Linux localhost.localdomain 4.10.1-dac_cpu+ #1 SMP Mon Apr 10 13:07:34 CEST 2017 armv7l armv7l armv7l GNU/Linux

I've tried a custom kernel – had problems with AppArmor. It seems like kernels derived from mainline kernels without Ubuntu patches doesn't have an option to bypass 
AppArmor for processes started by systemd. In that case I could not even install Avahi snap – AppArmor denied all system level hooks of Avahi. 

Tried Xenial kernel – doesn't boot. Didn't have enough time to investigate but all in all 4.4 is not an option as I need some commits incorporated in 4.8. Backporting them to 4.4 would've be an enormous work. 

But then I decided to try a Zesty kernel from a master branch. It works pretty well, Avahi installs and works. 
Initial boot installs all snaps, even core snap but then afterwards the core snap can't be updated when a new version comes out.  

Can it be related to kernel? 

Or maybe because of a failed device initialization when it was said "ERROR cannot retrieve request-id for making a request for a serial"?

Something else?

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$ snap change 23
Status  Spawn                 Ready                 Summary
Undone  2017-04-14T10:09:36Z  2017-04-13T13:44:19Z  Download snap "core" (1709) from channel "edge"
Done    2017-04-14T10:09:36Z  2017-04-13T13:44:17Z  Fetch and check assertions for snap "core" (1709)
Undone  2017-04-14T10:09:36Z  2017-04-13T13:44:21Z  Mount snap "core" (1709)
Undone  2017-04-14T10:09:36Z  2017-04-13T13:44:20Z  Stop snap "core" services
Undone  2017-04-14T10:09:36Z  2017-04-13T13:44:20Z  Remove aliases for snap "core"
Undone  2017-04-14T10:09:36Z  2017-04-13T13:44:19Z  Make current revision for snap "core" unavailable
Undone  2017-04-14T10:09:36Z  2017-04-13T13:44:19Z  Copy snap "core" data
Undone  2017-04-14T10:09:36Z  2017-04-13T13:44:19Z  Setup snap "core" (1709) security profiles
Undone  2017-04-14T10:09:36Z  2017-04-13T13:44:17Z  Make snap "core" (1709) available to the system
Error   2017-04-14T10:09:36Z  2017-04-13T13:44:16Z  Setup snap "core" (1709) security profiles (phase 2)
Hold    2017-04-14T10:09:36Z  2017-04-13T13:44:16Z  Set automatic aliases for snap "core"
Hold    2017-04-14T10:09:36Z  2017-04-13T13:44:16Z  Setup snap "core" aliases
Hold    2017-04-14T10:09:36Z  2017-04-13T13:44:16Z  Start snap "core" (1709) services
Hold    2017-04-14T10:09:36Z  2017-04-13T13:44:16Z  Clean up "core" (1709) install
Hold    2017-04-14T10:09:36Z  2017-04-13T13:44:16Z  Run configure hook of "core" snap if present

......................................................................
Setup snap "core" (1709) security profiles

2017-04-14T10:11:58Z INFO cannot auto connect network-manager:ppp to core:ppp: (slot auto-connection), existing connection state "network-manager:ppp core:ppp" in the way
2017-04-13T13:44:18Z INFO cannot auto connect core:core-support-plug to core:core-support: (plug auto-connection), existing connection state "core:core-support-plug core:core-support" in the way
2017-04-13T13:44:18Z INFO cannot auto connect alsa-utils:alsa to core:alsa: (slot auto-connection), existing connection state "alsa-utils:alsa core:alsa" in the way
2017-04-13T13:44:18Z INFO cannot auto connect core:core-support-plug to core:core-support: (slot auto-connection), existing connection state "core:core-support-plug core:core-support" in the way
2017-04-13T13:44:18Z INFO cannot auto connect network-manager:firewall-control to core:firewall-control: (slot auto-connection), existing connection state "network-manager:firewall-control core:firewall-control" in the way
2017-04-13T13:44:18Z INFO cannot auto connect avahi:network to core:network: (slot auto-connection), existing connection state "avahi:network core:network" in the way
2017-04-13T13:44:18Z INFO cannot auto connect avahi:network-bind to core:network-bind: (slot auto-connection), existing connection state "avahi:network-bind core:network-bind" in the way
2017-04-13T13:44:18Z INFO cannot auto connect avahi:network-control to core:network-control: (slot auto-connection), existing connection state "avahi:network-control core:network-control" in the way
2017-04-13T13:44:18Z INFO cannot auto connect network-manager:network-setup-observe to core:network-setup-observe: (slot auto-connection), existing connection state "network-manager:network-setup-observe core:network-setup-observe" in the way
2017-04-13T13:44:18Z INFO cannot auto connect network-manager:ppp to core:ppp: (slot auto-connection), existing connection state "network-manager:ppp core:ppp" in the way

......................................................................
Make snap "core" (1709) available to the system

2017-04-14T10:12:01Z INFO Requested system restart.

......................................................................
Setup snap "core" (1709) security profiles (phase 2)

2017-04-14T10:12:01Z INFO Waiting for restart...
2017-04-14T10:14:33Z INFO Waiting for restart...
2017-04-14T10:19:33Z INFO Waiting for restart...
2017-04-13T13:44:16Z ERROR cannot finish core installation, there was a rollback across reboot


Best regards, 

Denis S
denisnone at gmail.com