Add nvidia-ctk config generate-default command

This change adds a CLI command to generate a default config.
This config checks the host operating system to apply specific
modifications that were previously captured in static config
files.

These include:
* select /sbin/ldconfig or /sbin/ldconfig.real depending on which exists on the host
* set the user to allow device access on SUSE-based systems

Signed-off-by: Evan Lezar <elezar@nvidia.com>

cmd/nvidia-ctk/config/config.go

@@ -0,0 +1,50 @@
+/**
+# Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package config
+
+import (
+	createdefault "github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/config/create-default"
+	"github.com/sirupsen/logrus"
+	"github.com/urfave/cli/v2"
+)
+
+type command struct {
+	logger *logrus.Logger
+}
+
+// NewCommand constructs an config command with the specified logger
+func NewCommand(logger *logrus.Logger) *cli.Command {
+	c := command{
+		logger: logger,
+	}
+	return c.build()
+}
+
+// build
+func (m command) build() *cli.Command {
+	// Create the 'config' command
+	c := cli.Command{
+		Name:  "config",
+		Usage: "Interact with the NVIDIA Container Toolkit configuration",
+	}
+
+	c.Subcommands = []*cli.Command{
+		createdefault.NewCommand(m.logger),
+	}
+
+	return &c
+}

cmd/nvidia-ctk/config/create-default/create-default.go

@@ -0,0 +1,102 @@
+/**
+# Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+**/
+
+package defaultsubcommand
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	nvctkConfig "github.com/NVIDIA/nvidia-container-toolkit/internal/config"
+	"github.com/sirupsen/logrus"
+	"github.com/urfave/cli/v2"
+)
+
+type command struct {
+	logger *logrus.Logger
+}
+
+// options stores the subcommand options
+type options struct {
+	output string
+}
+
+// NewCommand constructs a default command with the specified logger
+func NewCommand(logger *logrus.Logger) *cli.Command {
+	c := command{
+		logger: logger,
+	}
+	return c.build()
+}
+
+// build creates the CLI command
+func (m command) build() *cli.Command {
+	opts := options{}
+
+	// Create the 'default' command
+	c := cli.Command{
+		Name:    "generate-default",
+		Aliases: []string{"default"},
+		Usage:   "Generate the default NVIDIA Container Toolkit configuration file",
+		Before: func(c *cli.Context) error {
+			return m.validateFlags(c, &opts)
+		},
+		Action: func(c *cli.Context) error {
+			return m.run(c, &opts)
+		},
+	}
+
+	c.Flags = []cli.Flag{
+		&cli.StringFlag{
+			Name:        "output",
+			Usage:       "Specify the file to output the generated configuration for to. If this is '' the configuration is ouput to STDOUT.",
+			Destination: &opts.output,
+		},
+	}
+
+	return &c
+}
+
+func (m command) validateFlags(c *cli.Context, opts *options) error {
+	return nil
+}
+
+func (m command) run(c *cli.Context, opts *options) error {
+	defaultConfig, err := nvctkConfig.GetDefaultConfigToml()
+	if err != nil {
+		return fmt.Errorf("unable to get default config: %v", err)
+	}
+
+	var output io.Writer
+	if opts.output == "" {
+		output = os.Stdout
+	} else {
+		outputFile, err := os.Create(opts.output)
+		if err != nil {
+			return fmt.Errorf("unable to create output file: %v", err)
+		}
+		defer outputFile.Close()
+		output = outputFile
+	}
+
+	_, err = defaultConfig.WriteTo(output)
+	if err != nil {
+		return fmt.Errorf("unable to write to output: %v", err)
+	}
+
+	return nil
+}

cmd/nvidia-ctk/main.go

@@ -20,6 +20,7 @@ import (
 	"os"
 
 	"github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/cdi"
+	"github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/config"
 	"github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/hook"
 	infoCLI "github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/info"
 	"github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/runtime"
@@ -79,6 +80,7 @@ func main() {
 		infoCLI.NewCommand(logger),
 		cdi.NewCommand(logger),
 		system.NewCommand(logger),
+		config.NewCommand(logger),
 	}
 
 	// Run the CLI