Add nvidia-ctk runtime apply command

This change adds an nvidia-ctk runtime apply command for applying modifications
to an OCI specification. This can be used for debugging or to apply modifications
to OCI specifications in use cases where the OCI-runtime shim cannot be invoked.

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

cmd/nvidia-ctk/runtime/list/list.go

@@ -0,0 +1,126 @@
+/**
+# Copyright (c) 2024, 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 list
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/urfave/cli/v2"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/config"
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/config/image"
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/logger"
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/runtime"
+)
+
+type command struct {
+	logger logger.Interface
+}
+
+// NewCommand constructs an list command with the specified logger
+func NewCommand(logger logger.Interface) *cli.Command {
+	c := command{
+		logger: logger,
+	}
+	return c.build()
+}
+
+// options defines the options that can be set for the CLI through options files,
+type options struct {
+	mode    string
+	envvars cli.StringSlice
+}
+
+func (m command) build() *cli.Command {
+	// Create a options struct to hold the parsed environment variables or command line flags
+	cfg := options{}
+
+	// Create the 'configure' command
+	configure := cli.Command{
+		Name:  "list",
+		Usage: "List the modifications made to the OCI runtime specification",
+		Before: func(c *cli.Context) error {
+			return m.validateFlags(c, &cfg)
+		},
+		Action: func(c *cli.Context) error {
+			return m.list(c, &cfg)
+		},
+	}
+
+	configure.Flags = []cli.Flag{
+		&cli.StringFlag{
+			Name:        "mode",
+			Usage:       "override the runtime mode a specified in the config file",
+			Destination: &cfg.mode,
+		},
+		&cli.StringSliceFlag{
+			Name:        "envvar",
+			Aliases:     []string{"e"},
+			Usage:       "add an envvar to the container definition",
+			Destination: &cfg.envvars,
+		},
+	}
+
+	return &configure
+}
+
+func (m command) validateFlags(c *cli.Context, cfg *options) error {
+	return nil
+}
+
+// list executes the list command.
+func (m command) list(c *cli.Context, cfg *options) error {
+	toolkitConfig, err := config.GetDefault()
+	if err != nil {
+		return fmt.Errorf("failed to generate default config: %w", err)
+	}
+
+	if cfg.mode != "" {
+		toolkitConfig.NVIDIAContainerRuntimeConfig.Mode = cfg.mode
+	}
+
+	container, err := image.New(
+		image.WithEnv(cfg.envvars.Value()),
+	)
+	if err != nil {
+		return fmt.Errorf("failed to construct container image: %w", err)
+	}
+
+	modifier, err := runtime.NewSpecModifier(m.logger, toolkitConfig, container)
+	if err != nil {
+		return fmt.Errorf("failed to contruct OCI runtime specification modifier: %w", err)
+	}
+	// TODO: We should handle this more cleanly.
+	if modifier == nil {
+		return fmt.Errorf("no modifications required")
+	}
+
+	spec := specs.Spec{}
+	if err := modifier.Modify(&spec); err != nil {
+		return fmt.Errorf("faile to apply modification to empty spec: %w", err)
+	}
+
+	specJSON, err := json.MarshalIndent(spec, "", "  ")
+	if err != nil {
+		return fmt.Errorf("failed to marshal OCI spec to JSON: %w", err)
+	}
+	fmt.Printf("%v", string(specJSON))
+
+	return nil
+}

cmd/nvidia-ctk/runtime/runtime.go

@@ -20,6 +20,7 @@ import (
 	"github.com/urfave/cli/v2"
 
 	"github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/runtime/configure"
+	"github.com/NVIDIA/nvidia-container-toolkit/cmd/nvidia-ctk/runtime/list"
 	"github.com/NVIDIA/nvidia-container-toolkit/internal/logger"
 )
 
@@ -44,6 +45,7 @@ func (m runtimeCommand) build() *cli.Command {
 
 	runtime.Subcommands = []*cli.Command{
 		configure.NewCommand(m.logger),
+		list.NewCommand(m.logger),
 	}
 
 	return &runtime