Adds a secret skip preflight environment variable (#2364)

* Adds a secret skip preflight environment variable

TL;DR
-----

Supports the `SKIP_HOST_PREFLIGHTS` environment variable to skip the
preflight checks. Thjis is not documented and not for general use.

Details
-------

Offers a "hidden" way to skip preflight checks by setting the
environment variable `SKIP_HOST_PREFLIGHTS`. I'm adding the flag to
support our Instruqt labs, since the Instruqt environment require a
wildcard DNS entry that causes the host preflights to fail.

I decided on this approach to avoid teaching any bad habits by telling
the user to use `--ignore-host-preflights` when teaching them about
the Embedded Cluster. I wanted instead to avoid the checks on their
behalf without them realized it. This variable is not deliberately not
documented to avoid similar encouragement of bad habits.

* Reformats code

* Restores missing brace

* Moves to the Linux pre install per @sgalsaleh review

* Checks specific values per @sgalsaleh review

* Fixes failing test

Author: crdant

cmd/installer/cli/install.go

@@ -449,6 +449,10 @@ func preRunInstallCommon(cmd *cobra.Command, flags *InstallCmdFlags, rc runtimec
 }
 
 func preRunInstallLinux(cmd *cobra.Command, flags *InstallCmdFlags, rc runtimeconfig.RuntimeConfig) error {
+	if !cmd.Flags().Changed("skip-host-preflights") && (os.Getenv("SKIP_HOST_PREFLIGHTS") == "1" || os.Getenv("SKIP_HOST_PREFLIGHTS") == "true") {
+		flags.skipHostPreflights = true
+	}
+
 	if os.Getuid() != 0 {
 		return fmt.Errorf("install command must be run as root")
 	}

cmd/installer/cli/install_test.go

@@ -14,7 +14,9 @@ import (
 	"github.com/replicatedhq/embedded-cluster/pkg/prompts"
 	"github.com/replicatedhq/embedded-cluster/pkg/prompts/plain"
 	"github.com/replicatedhq/embedded-cluster/pkg/release"
+	"github.com/replicatedhq/embedded-cluster/pkg/runtimeconfig"
 	kotsv1beta1 "github.com/replicatedhq/kotskinds/apis/kots/v1beta1"
+	"github.com/spf13/cobra"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -607,3 +609,97 @@ func Test_verifyProxyConfig(t *testing.T) {
 		})
 	}
 }
+
+func Test_preRunInstall_SkipHostPreflightsEnvVar(t *testing.T) {
+	tests := []struct {
+		name                   string
+		envVarValue            string
+		flagValue              *bool // nil means not set, true/false means explicitly set
+		expectedSkipPreflights bool
+	}{
+		{
+			name:                   "env var set to 1, no flag",
+			envVarValue:            "1",
+			flagValue:              nil,
+			expectedSkipPreflights: true,
+		},
+		{
+			name:                   "env var set to true, no flag",
+			envVarValue:            "true",
+			flagValue:              nil,
+			expectedSkipPreflights: true,
+		},
+		{
+			name:                   "env var set, flag explicitly false (flag takes precedence)",
+			envVarValue:            "1",
+			flagValue:              boolPtr(false),
+			expectedSkipPreflights: false,
+		},
+		{
+			name:                   "env var set, flag explicitly true",
+			envVarValue:            "1",
+			flagValue:              boolPtr(true),
+			expectedSkipPreflights: true,
+		},
+		{
+			name:                   "env var not set, no flag",
+			envVarValue:            "",
+			flagValue:              nil,
+			expectedSkipPreflights: false,
+		},
+		{
+			name:                   "env var not set, flag explicitly false",
+			envVarValue:            "",
+			flagValue:              boolPtr(false),
+			expectedSkipPreflights: false,
+		},
+		{
+			name:                   "env var not set, flag explicitly true",
+			envVarValue:            "",
+			flagValue:              boolPtr(true),
+			expectedSkipPreflights: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Set up environment variable
+			if tt.envVarValue != "" {
+				t.Setenv("SKIP_HOST_PREFLIGHTS", tt.envVarValue)
+			}
+
+			// Create a mock cobra command to simulate flag behavior
+			cmd := &cobra.Command{}
+			flags := &InstallCmdFlags{}
+
+			// Add the flag to the command (similar to addInstallFlags)
+			cmd.Flags().BoolVar(&flags.skipHostPreflights, "skip-host-preflights", false, "Skip host preflight checks")
+
+			// Set the flag if explicitly provided in test
+			if tt.flagValue != nil {
+				err := cmd.Flags().Set("skip-host-preflights", fmt.Sprintf("%t", *tt.flagValue))
+				require.NoError(t, err)
+			}
+
+			// Create a minimal runtime config for the test
+			rc := runtimeconfig.New(nil)
+
+			// Call preRunInstall (this would normally require root, but we're just testing the flag logic)
+			// We expect this to fail due to non-root execution, but we can check the flag value before it fails
+			err := preRunInstallLinux(cmd, flags, rc)
+
+			// The function will fail due to non-root check, but we can verify the flag was set correctly
+			// by checking the flag value before the root check fails
+			assert.Equal(t, tt.expectedSkipPreflights, flags.skipHostPreflights)
+
+			// We expect an error due to non-root execution
+			assert.Error(t, err)
+			assert.Contains(t, err.Error(), "install command must be run as root")
+		})
+	}
+}
+
+// Helper function to create bool pointer
+func boolPtr(b bool) *bool {
+	return &b
+}