'az aks create' error if name contains character underscore(_)

[wcc8088]

az feedback auto-generates most of the information requested below, as of CLI version 2.0.62

Describe the bug

$> az aks create --resource-group wooccdocker -n "aks_woocccluster" --node-count 1
--name cannot exceed 63 characters and can only contain letters, numbers, or dashes (-).

Expected behavior

According to the document, underscore can be used for names.

Entity	Scope	Length	Valid Characters
managedClusters	resource group	1-63	Alphanumerics, underscores, and hyphens.Start and end with alphanumeric.
openShiftManagedClusters	resource group	1-30	Alphanumerics.

https://docs.microsoft.com/en-us/azure/azure-resource-manager/management/resource-name-rules#microsoftcontainerservice

Environment summary
$ az --version
azure-cli 2.22.0

core 2.22.0
telemetry 1.0.6

Extensions:
subscription 0.1.4
blueprint 0.1.1
account 0.2.1

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @Azure/aks-pm.

Issue Details

---

az feedback auto-generates most of the information requested below, as of CLI version 2.0.62

Describe the bug

$> az aks create --resource-group wooccdocker -n "aks_woocccluster" --node-count 1
--name cannot exceed 63 characters and can only contain letters, numbers, or dashes (-).

Expected behavior

According to the document, underscore can be used for names.

Entity	Scope	Length	Valid Characters
managedClusters	resource group	1-63	Alphanumerics, underscores, and hyphens.Start and end with alphanumeric.
openShiftManagedClusters	resource group	1-30	Alphanumerics.

https://docs.microsoft.com/en-us/azure/azure-resource-manager/management/resource-name-rules#microsoftcontainerservice

Environment summary
$ az --version
azure-cli 2.22.0

core 2.22.0
telemetry 1.0.6

Extensions:
subscription 0.1.4
blueprint 0.1.1
account 0.2.1

Author:	wcc8088
Assignees:	-
Labels:	AKS, Service Attention, needs-triage, question
Milestone:	-

[C4RTON]

We got the same problem, can you investigate on it ?

[yonzhan]

AKS service team should look into this

[vcariven]

In my case, it happens when using the aks-preview extension which might be the effective root cause :

cli.azure.cli.core.commands: The behavior of this command has been altered by the following extension: aks-preview
cli.azure.cli.core.util: azure.cli.core.util.handle_exception is called with an exception:
cli.azure.cli.core.util: Traceback (most recent call last):
  File "/opt/az/lib/python3.6/site-packages/knack/cli.py", line 231, in invoke
    cmd_result = self.invocation.execute(args)
  File "/opt/az/lib/python3.6/site-packages/azure/cli/core/commands/__init__.py", line 645, in execute
    self._validation(expanded_arg)
  File "/opt/az/lib/python3.6/site-packages/knack/invocation.py", line 113, in _validation
    self._validate_arg_level(parsed_ns)
  File "/opt/az/lib/python3.6/site-packages/azure/cli/core/commands/__init__.py", line 853, in _validate_arg_level
    validator(**self._build_kwargs(validator, ns))
  File "/home/vagrant/.azure/cliextensions/aks-preview/azext_aks_preview/_validators.py", line 91, in validate_linux_host_name
    raise CLIError('--name cannot exceed 63 characters and can only contain '
knack.util.CLIError: --name cannot exceed 63 characters and can only contain letters, numbers, or dashes (-).

cli.azure.cli.core.azclierror: --name cannot exceed 63 characters and can only contain letters, numbers, or dashes (-).
az_command_data_logger: --name cannot exceed 63 characters and can only contain letters, numbers, or dashes (-).

Where the function validate_linux_host_name is called to validate the AKS cluster name and does not allow the underscore _ character.

• https://github.com/Azure/azure-cli-extensions/blob/main/src/aks-preview/azext_aks_preview/_validators.py#L79
  Maybe the issue could be transfered to the https://github.com/Azure/azure-cli-extensions project ?

Thank you for your feedback. This has been routed to the support team for assistance.