Installation fails on Debian unstable

[nmeyerhans]

Using image with URN Debian:debian-sid-daily:sid-gen2:latest, the ConfigurationforLinux extension fails. Output visible in the Azure Portal and in /var/log/waagent.log on the VM follows:

Portal:

{"code":"VMExtensionHandlerNonTransientError","message":"The handler for VM extension type 'Microsoft.GuestConfiguration.ConfigurationforLinux' has reported terminal failure for VM extension 'AzurePolicyforLinux' with error message: '[ExtensionOperationError] Non-zero exit code: 1, /var/lib/waagent/Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80/bin/guest-configuration-shim install\n[stdout]\n\n\n[stderr]\n/var/lib/waagent/Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80/bin/guest-configuration-shim: line 121: VERSION_ID: unbound variable\n'.\r\n    \r\n'Install handler failed for the extension. More information on troubleshooting is available at https://aka.ms/vmextensionlinuxtroubleshoot'"}

VM:

2025-02-05T16:56:06.759318Z INFO ExtHandler 
2025-02-05T16:56:06.759403Z INFO ExtHandler Fetched new vmSettings [HostGAPlugin correlation ID: 888ac619-7eb0-4d29-b210-c8dd27a7f4d2 eTag: 196617041067
4056617 source: FastTrack]
2025-02-05T16:56:06.760195Z INFO ExtHandler ExtHandler 
2025-02-05T16:56:06.760253Z INFO ExtHandler ExtHandler ProcessExtensionsGoalState started [etag_1966170410674056617 channel: HostGAPlugin source: FastTrack activity: ef8d741d-e3a4-497c-ad3e-a0f8722684a4 correlation 987a8b17-2917-47e9-8411-f3089b572e92 created: 2025-02-05T16:56:05.421776Z]
2025-02-05T16:56:06.760576Z INFO ExtHandler ExtHandler Downloading extension manifest
2025-02-05T16:56:06.789216Z INFO ExtHandler [Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80] Target handler state: enabled [etag_1966170410674056617]
2025-02-05T16:56:06.789407Z INFO ExtHandler [Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80] [Enable] current handler state is: notinstalled
2025-02-05T16:56:06.789601Z INFO ExtHandler ExtHandler Downloading extension package
2025-02-05T16:56:07.102994Z INFO ExtHandler ExtHandler Unzipping extension package: /var/lib/waagent/Microsoft.GuestConfiguration.ConfigurationforLinux__1.26.80.zip
2025-02-05T16:56:07.193425Z INFO ExtHandler [Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80] Initializing extension Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80
2025-02-05T16:56:07.194133Z INFO ExtHandler [Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80] Update settings file: 0.settings
2025-02-05T16:56:07.194320Z INFO ExtHandler [Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80] Install extension [bin/guest-configuration-shim install]
2025-02-05T16:56:07.194498Z INFO ExtHandler [Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80] Executing command: /var/lib/waagent/Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80/bin/guest-configuration-shim install with environment variables: {"AZURE_GUEST_AGENT_UNINSTALL_CMD_EXIT_CODE": "NOT_RUN", "AZURE_GUEST_AGENT_EXTENSION_PATH": "/var/lib/waagent/Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80", "AZURE_GUEST_AGENT_EXTENSION_VERSION": "1.26.80", "AZURE_GUEST_AGENT_WIRE_PROTOCOL_ADDRESS": "168.63.129.16", "ConfigSequenceNumber": "0", "AZURE_GUEST_AGENT_EXTENSION_SUPPORTED_FEATURES": "[{\"Key\": \"ExtensionTelemetryPipeline\", \"Value\": \"1.0\"}]"}
2025-02-05T16:56:09.197464Z ERROR ExtHandler ExtHandler Event: name=Microsoft.GuestConfiguration.ConfigurationforLinux, op=Install, message=[ExtensionOperationError] Non-zero exit code: 1, /var/lib/waagent/Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80/bin/guest-configuration-shim install
[stdout]


[stderr]
/var/lib/waagent/Microsoft.GuestConfiguration.ConfigurationforLinux-1.26.80/bin/guest-configuration-shim: line 121: VERSION_ID: unbound variable
, duration=0
2025-02-05T16:56:09.198454Z INFO ExtHandler ExtHandler ProcessExtensionsGoalState completed [etag_1966170410674056617 2438 ms]

2025-02-05T16:56:09.212129Z INFO ExtHandler ExtHandler Extension status: [('Microsoft.GuestConfiguration.ConfigurationforLinux', 'NotReady')]
2025-02-05T16:56:09.212422Z INFO ExtHandler ExtHandler All extensions in the goal state have reached a terminal state: [('Microsoft.GuestConfiguration.ConfigurationforLinux', 'NotReady')]

[nmeyerhans]

The problem is in the guest-configuration-shim script, in the get_linux_version function:

get_linux_version() {
    if [ -f /etc/os-release ]; then
        . /etc/os-release
        LINUX_DISTRO_VERSION=$VERSION_ID
    ...
    fi
    if [ -z $LINUX_DISTRO_VERSION ]; then
        print_error "Unexpected error occurred while getting the distro version."
        exit 1
    fi

In the case of pre-release Debian versions, VERSION_ID is not present in /etc/os-release and is thus unset. So the -z test later fails, the the script exits.

I suggest handling a special case where $ID=debian and VERSION_ID is unset. In that case, set LINUX_DISTRO_VERSION to some arbitrary large number (999 or something) such that it passes your minimum version checks elsewhere.