feat: support new ACL os-release (ID=azurelinux, VARIANT_ID=azurecontainerlinux)

[aadhar-agarwal]

Summary

ACL is changing its /etc/os-release from ID=azurecontainerlinux to ID=azurelinux + VARIANT_ID=azurecontainerlinux. This PR updates all detection logic to support both formats. This is similar to how OSGuard has its os-release.

Key Changes

• isACL() now accepts OS_VARIANT and matches either the legacy or new os-release format
• isMarinerOrAzureLinux() / isAzureLinux() explicitly exclude ACL to prevent it from entering Azure Linux code paths (since ACL is Flatcar-based). Without this, there would be a lot of changes which does not make sense because it is an immutable os.
• All isACL call sites updated to pass $OS_VARIANT across provisioning scripts, VHD build scripts, and packer configs
• Custom scripts updated to detect ACL via both old and new formats
• ACL sysext extension-release updated to ID=azurelinux
• Pipeline switched to aclpreview / aclpreview-arm64 source images - replicated to westus, westus2, westus3 and eastus
• E2E tests updated to validate new os-release format
• Snapshot test data regenerated via make generate

Backward Compatibility

isACL() still matches legacy ID=azurecontainerlinux, so older VHDs continue to work - We can remove this check later on

Testing

[TEST All VHDs] AKS Linux VHD Build - Msft Tenant

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

[Copilot]

Pull request overview

Adds support across VHD build + provisioning scripts for the updated Azure Container Linux /etc/os-release format where ID=azurelinux and VARIANT_ID=azurecontainerlinux.

Changes:

• Update ACL detection logic in Linux cloud-init artifacts to recognize ID=azurelinux + VARIANT_ID=azurecontainerlinux.
• Propagate/use OS_VARIANT (from VARIANT_ID) in packer scripts and VHD content tests to keep ACL-specific branching correct.
• Refresh e2e validations, packer ACL customdata, pipeline SIG source variables, and golden testdata snapshots to match the new os-release format.

Reviewed changes

Copilot reviewed 23 out of 87 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
vhdbuilder/packer/test/linux-vhd-content-test.sh	Treat ACL as AZURELINUX with an ACL variant and update sysext validation logic to use isACL.
vhdbuilder/packer/pre-install-dependencies.sh	Capture OS_VARIANT from VARIANT_ID for downstream branching.
vhdbuilder/packer/post-install-dependencies.sh	Capture OS_VARIANT and use isACL "$OS" "$OS_VARIANT" for disk sizing logic.
vhdbuilder/packer/post-deprovision-walinuxagent.sh	Defensively skip WALinuxAgent manifest install when VARIANT_ID=AZURECONTAINERLINUX.
vhdbuilder/packer/packer_source.sh	Update ACL checks to pass the OS variant into isACL.
vhdbuilder/packer/install-ig.sh	Skip IG installation for ACL using isACL "${OS}" "${OS_VARIANT}".
vhdbuilder/packer/install-dependencies.sh	Exclude ACL from AzureLinux3 artifact streaming configuration.
vhdbuilder/packer/acl-customdata.yaml / acl-customdata.json	Update sysext extension-release ID to azurelinux.
pkg/agent/testdata/**/CustomData	Update snapshot testdata payloads to reflect new ACL os-release values.
parts/linux/cloud-init/artifacts/init-aks-custom-cloud*.sh	Detect ACL when ID=azurelinux and VARIANT_ID=azurecontainerlinux.
parts/linux/cloud-init/artifacts/cse_helpers.sh	Introduce ACL variant constant; ensure isAzureLinux*/isMarinerOrAzureLinux exclude ACL; extend isACL to match new format; adjust package URI selection for ACL.
parts/linux/cloud-init/artifacts/cse_config.sh / cis.sh	Pass OS_VARIANT into isACL checks.
e2e/scenario_test.go	Validate ACL /etc/os-release contains both ID=azurelinux and VARIANT_ID=azurecontainerlinux.
.pipelines/.vsts-vhd-builder-release.yaml	Update ACL SIG source image name/version to aclpreview and new versions.

[Copilot]

Pull request overview

This PR updates OS detection across VHD build, provisioning (CSE/cloud-init), and tests to support the Azure Container Linux /etc/os-release change from ID=azurecontainerlinux to ID=azurelinux with VARIANT_ID=azurecontainerlinux, while keeping legacy detection working.

Changes:

• Extend isACL() to accept/use OS_VARIANT and match both legacy and new os-release formats; update key call sites to pass OS_VARIANT.
• Explicitly exclude ACL from Azure Linux detection paths (isMarinerOrAzureLinux / isAzureLinux) to avoid treating ACL as mutable Azure Linux.
• Update ACL ignition/customdata and e2e/pipeline inputs to validate and build against the new os-release format and preview source images.

Reviewed changes

Copilot reviewed 23 out of 87 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
parts/linux/cloud-init/artifacts/cse_helpers.sh	Updates isACL() signature/logic; ensures AzureLinux detection helpers exclude ACL; adjusts package URI selection for ACL to use Flatcar entries.
parts/linux/cloud-init/artifacts/init-aks-custom-cloud.sh	Detects ACL by either legacy ID=azurecontainerlinux or new ID=azurelinux + VARIANT_ID=azurecontainerlinux.
parts/linux/cloud-init/artifacts/init-aks-custom-cloud-operation-requests.sh	Same ACL detection update as above.
parts/linux/cloud-init/artifacts/cse_config.sh	Passes OS_VARIANT into isACL for ACL-specific CA trust handling.
parts/linux/cloud-init/artifacts/cis.sh	Passes OS_VARIANT into isACL when deciding to skip Ubuntu-only CIS steps.
vhdbuilder/packer/pre-install-dependencies.sh	Captures OS_VARIANT from VARIANT_ID for downstream detection use during VHD build.
vhdbuilder/packer/post-install-dependencies.sh	Uses isACL "$OS" "$OS_VARIANT" when applying Flatcar/ACL-specific disk sizing logic.
vhdbuilder/packer/packer_source.sh	Updates multiple file-copy skip conditions to call isACL with OS_VARIANT.
vhdbuilder/packer/install-dependencies.sh	Ensures Azure Linux-specific flows exclude ACL (e.g., Artifact Streaming gating) and relies on OS_VARIANT parsing.
vhdbuilder/packer/install-ig.sh	Skips IG installation for ACL using isACL "${OS}" "${OS_VARIANT}".
vhdbuilder/packer/post-deprovision-walinuxagent.sh	Adds a defensive skip for ACL based on VARIANT_ID=AZURECONTAINERLINUX; improves skip log message.
vhdbuilder/packer/test/linux-vhd-content-test.sh	Treats ACL as OS=AZURELINUX with OS_VARIANT=AZURECONTAINERLINUX; uses isACL for Flatcar/ACL system-extension expectations.
vhdbuilder/packer/acl-customdata.yaml	Updates sysext extension-release ID to azurelinux.
vhdbuilder/packer/acl-customdata.json	Regenerates ignition JSON to reflect ID=azurelinux in extension-release payload.
e2e/scenario_test.go	Updates ACL scenario validation to expect ID=azurelinux and VARIANT_ID=azurecontainerlinux in /etc/os-release.
.pipelines/.vsts-vhd-builder-release.yaml	Switches ACL source SIG images to aclpreview / aclpreview-arm64 and updates versions.
pkg/agent/testdata/MarinerV2+Kata/CustomData	Regenerated snapshot test data (compressed custom data).
pkg/agent/testdata/CustomizedImage/CustomData	Regenerated snapshot test data (compressed custom data).

[Copilot]

Pull request overview

This PR updates OS detection across AgentBaker provisioning scripts, VHD build scripts, and tests to support Azure Container Linux (ACL) switching /etc/os-release from ID=azurecontainerlinux to ID=azurelinux with VARIANT_ID=azurecontainerlinux, while ensuring ACL does not accidentally follow Azure Linux code paths.

Changes:

• Extended ACL detection (isACL) to accept/use an OS variant and recognize both legacy and new /etc/os-release formats.
• Updated VHD builder scripts/tests and packer logic to pass/use OS_VARIANT so ACL is handled correctly when ID=azurelinux.
• Updated ACL-related customdata and e2e assertions, plus regenerated snapshot testdata (make generate).

Reviewed changes

Copilot reviewed 23 out of 87 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
vhdbuilder/packer/test/linux-vhd-content-test.sh	Treat ACL as OS=AZURELINUX + OS_VARIANT=AZURECONTAINERLINUX and use isACL for sysext checks.
vhdbuilder/packer/pre-install-dependencies.sh	Read VARIANT_ID and pass it into isACL gating.
vhdbuilder/packer/post-install-dependencies.sh	Read VARIANT_ID and use isACL for sizing logic.
vhdbuilder/packer/post-deprovision-walinuxagent.sh	Add defensive skip when VARIANT_ID=AZURECONTAINERLINUX.
vhdbuilder/packer/packer_source.sh	Pass OS_VARIANT into isACL call sites during file staging.
vhdbuilder/packer/install-ig.sh	Use isACL "${OS}" "${OS_VARIANT}" to skip IG on ACL.
vhdbuilder/packer/install-dependencies.sh	Pass OS_VARIANT into isACL call sites; exclude ACL from AzureLinux-only paths.
vhdbuilder/packer/acl-customdata.yaml	Update extension-release ID to azurelinux.
vhdbuilder/packer/acl-customdata.json	Regenerated ignition JSON reflecting ID=azurelinux.
pkg/agent/testdata/MarinerV2+Kata/CustomData	Snapshot regeneration output.
pkg/agent/testdata/CustomizedImage/CustomData	Snapshot regeneration output.
parts/linux/cloud-init/artifacts/init-aks-custom-cloud.sh	Detect ACL by (ID=azurelinux && VARIANT_ID=azurecontainerlinux) in addition to legacy.
parts/linux/cloud-init/artifacts/init-aks-custom-cloud-operation-requests.sh	Same ACL detection update as above.
parts/linux/cloud-init/artifacts/cse_helpers.sh	Update isACL signature/logic; exclude ACL from AzureLinux code paths; adjust package URI selection for ACL.
parts/linux/cloud-init/artifacts/cse_config.sh	Pass OS_VARIANT into isACL for CA-trust behavior.
parts/linux/cloud-init/artifacts/cis.sh	Pass OS_VARIANT into isACL.
e2e/scenario_test.go	Validate new /etc/os-release format (ID + VARIANT_ID).
.pipelines/.vsts-vhd-builder-release.yaml	Switch ACL build source images to aclpreview / aclpreview-arm64.

[aadhar-agarwal]

The 2 ACL AgentBaker E2E failures are expected as we are changing the id to be azurelinux instead of azurecontainerlinux