AppArmor blocks 'mknod'

[AlexStepanov]

Hello,

I'm trying to communicate with a basler camera through their pylon driver over ethernet.

When I login over ssh, I can successfully ping the camera. But when I start my application, it throws an exception (Failed to create embedded nodemap).

Looking through the logbook, I saw that apparmor denied the operation "mknod"

Installing the application (after compiling it for amd64) with --devmode on my computer, everything works fine. But without --devmode I receive the same exception.

I tried to add different plugs to my snapcraft.yml (block-devices, classic-support, etc.) but I still receive the same errors.

Are there any additional plugs or settings I can use, to enable the driver to setup a connection to the camera?

Best Regards
Alexander Stepanov

[CodeShepherd]

Did you install your snap on the ctrlX CORE also in devmode?

mknod seems to try to add folders and files to system to did you add the system-files plug?

For the plug and slot mechanism there are useful information in the docs of snapcraft.io.

[AlexStepanov · Accepted solution]

Thank you for the hint! I was also in contact with the support from Basler and I was missing the environment variable "GENICAM_CACHE_V3_1", which points to a directory, where the pylon library can temporarily store xml files containing camera informations. The default location is write protected, thus it was blocked by AppArmor.

Pointing the environemnt variable to $TMP solved my problem.

snapcraft.yaml

...
apps:
  baslercam:
    command: connectcamera
    plugs: [...]
    environment:      
      GENICAM_CACHE_V3_1: $TMP

...