Troubleshoot common issues with confidential containers

This article provides solutions to common issues with confidential containers on Azure Container Instances.

Common issues

You might experience the following issues and errors when you deploy confidential containers:

• Policy failures:

  Deployment Failed.
  ErrorMessage=failed to create containerd task: failed to create shim task:
  uvm::Policy: failed to modify utility VM configuration: guest modify: guest RPC failure:
  error creating Rego policy: rego compilation failed: rego compilation failed: 4 errors occurred:
  

  Deployment Failed.
  ErrorMessage=failed to create containerd task: failed to create shim task:
  uvm::Policy: failed to modify utility VM configuration: guest modify:guest RPC failure:
  error creating Rego policy: rego compilation failed: rego compilation failed: 1 error occurred:
  policy.rego:48 rego_parse_error: non-terminated string;
  

  Container creation denied due to policy: create_container not allowed by policy. 
  Errors: [invalid command].
  

  Denied by policy: rule for mount_device is missing from policy: unknown.
  

  Failed to create containerd task: failed to create shim task: failed to mount container storage:
  failed to add LCOW layer: failed to add SCSI layer: failed to modify UVM with new SCSI mount:
  guest modify: guest RPC failure: mounting scsi device controller 3 lun 2 onto /run/mounts/m4
  denied by policy: mount_device not allowed by policy. Errors: [deviceHash not found].
  

  Container creation denied due to policy: create_container not allowed by policy. 
  

• A policy enforces a new framework:

  Failed to create containerd task: failed to create shim task: failed to mount container storage:
  guest modify: guest RPC failure: overlay creation denied by policy: mount_overlay not allowed by policy.
  Errors: [framework_svn is ahead of the current svn: 1.1.0 > 0.1.0].
  

• Invalid base64 confidential computing enforcement (CCE) policy:

  The CCE Policy is not valid Base64.
  

• Limitation - 120 kilobytes (KB) limit on the CCE policy:

  Failed to create containerd task: failed to create shim task: error while creating the compute system:
  hcs::CreateComputeSystem <compute system id>@vm: The requested operation failed.: unknown.\r\n;
  The container group provisioning has failed. Refer to 'DeploymentFailedReason' event for more details.;
  

  Failed to create containerd task: failed to create shim task: task with id: '<task id>' cannot be created in pod: '<pod>'
  which is not running: failed precondition.\r\n;The container group provisioning has failed.
  Refer to 'DeploymentFailedReason' event for more details.
  

• Device hash isn't found:

  Denied by policy: rule for mount_device is missing from policy: unknown.
  

  Failed to create containerd task: failed to create shim task: failed to mount container storage:
  failed to add LCOW layer: failed to add SCSI layer: failed to modify UVM with new SCSI mount:
  guest modify: guest RPC failure: mounting scsi device controller 3 lun 2 onto /run/mounts/m4
  denied by policy: mount_device not allowed by policy. Errors: [deviceHash not found]
  

• Other issues:

  • Logs don't show up.
  • The exec functionality doesn't work.
  • Subscription deployment times out after 30 minutes.
  • Liveness probe with disallowed policy.
  • Exit code 139.

Cause

In most cases, these issues occur due to the CCE policy.

Solution

• If you experience any policy failures, regenerate the CCE policy and retry the deployment.

• If the CCE policy enforces a framework, revert to an older framework svn.

• If the device hash isn't found or there's an issue with an image, clear the cache and regenerate the CCE policy.

  To clean the cache, run the docker rmi <image_name>:<tag> command. To clean all images in the cache, run the docker rmi $(docker images -a -q) command. To inspect the missing hash, run the docker inspect <image_name>:<tag> command.

Contact us for help

If you have questions or need help, create a support request, or ask Azure community support. You can also submit product feedback to Azure feedback community.