Add support for Flatcar Container Linux

Signed-off-by: Johanan Liebermann <jliebermann@microsoft.com>

pkg/util/helpers_linux.go

@@ -70,6 +70,8 @@ func getOSVersion(osReleasePath string) (string, error) {
 		return getDebianVersion(osReleaseMap), nil
 	case "azurelinux":
 		return getDebianVersion(osReleaseMap), nil
+	case "flatcar":
+		return getDebianVersion(osReleaseMap), nil
 	default:
 		return "", fmt.Errorf("Unsupported ID in /etc/os-release: %q", osReleaseMap["ID"])
 	}

pkg/util/helpers_linux_test.go

@@ -93,6 +93,12 @@ func TestGetOSVersionLinux(t *testing.T) {
 			expectedOSVersion: "azurelinux 3.0.20240328",
 			expectErr:         false,
 		},
+		{
+			name:              "flatcar",
+			fakeOSReleasePath: "testdata/os-release-flatcar",
+			expectedOSVersion: "flatcar 4372.0.1",
+			expectErr:         false,
+		},
 		{
 			name:              "Unknown",
 			fakeOSReleasePath: "testdata/os-release-unknown",

pkg/util/testdata/os-release-flatcar

@@ -0,0 +1,13 @@
+NAME="Flatcar Container Linux by Kinvolk"
+ID=flatcar
+ID_LIKE=coreos
+VERSION=4372.0.1
+VERSION_ID=4372.0.1
+BUILD_ID=2025-07-06-2244
+SYSEXT_LEVEL=1.0
+PRETTY_NAME="Flatcar Container Linux by Kinvolk 4372.0.1 (Oklo)"
+ANSI_COLOR="38;5;75"
+HOME_URL="https://flatcar.org/"
+BUG_REPORT_URL="https://issues.flatcar.org"
+FLATCAR_BOARD="amd64-usr"
+CPE_NAME="cpe:2.3:o:flatcar-linux:flatcar_linux:4372.0.1:*:*:*:*:*:*:*"