runtime: Handle the transient store options

This handles the transient store options from the container/storage
configuration in the runtime/engine.

Changes are:
 * Print transient store status in `podman info`
 * Print transient store status in runtime debug output
 * Add --transient-store argument to override config option
 * Propagate config state to conmon cleanup args so the callback podman
   gets the same config.

Note: This doesn't really change any behaviour yet (other than the changes
in containers/storage).

Signed-off-by: Alexander Larsson <alexl@redhat.com>

cmd/podman/root.go

@@ -464,6 +464,8 @@ func rootFlags(cmd *cobra.Command, podmanConfig *entities.PodmanConfig) {
 		pFlags.StringVar(&podmanConfig.Runroot, runrootFlagName, "", "Path to the 'run directory' where all state information is stored")
 		_ = cmd.RegisterFlagCompletionFunc(runrootFlagName, completion.AutocompleteDefault)
 
+		pFlags.BoolVar(&podmanConfig.TransientStore, "transient-store", false, "Enable transient container storage")
+
 		runtimeFlagName := "runtime"
 		pFlags.StringVar(&podmanConfig.RuntimePath, runtimeFlagName, podmanConfig.ContainersConfDefaultsRO.Engine.OCIRuntime, "Path to the OCI-compatible binary used to run containers.")
 		_ = cmd.RegisterFlagCompletionFunc(runtimeFlagName, completion.AutocompleteDefault)

docs/source/markdown/podman-info.1.md

@@ -146,6 +146,7 @@ store:
   imageStore:
     number: 5
   runRoot: /run/user/3267/containers
+  transientStore: false
   volumePath: /home/dwalsh/.local/share/containers/storage/volumes
 version:
   APIVersion: 4.0.0
@@ -263,7 +264,8 @@ $ podman info --format json
       "number": 5
     },
     "runRoot": "/run/user/3267/containers",
-    "volumePath": "/home/dwalsh/.local/share/containers/storage/volumes"
+    "volumePath": "/home/dwalsh/.local/share/containers/storage/volumes",
+    "transientStore": false
   },
   "registries": {
     "search": [

docs/source/markdown/podman.1.md

@@ -162,6 +162,14 @@ Path to the tmp directory, for libpod runtime content. Defaults to `$XDG_RUNTIME
 
 NOTE --tmpdir is not used for the temporary storage of downloaded images.  Use the environment variable `TMPDIR` to change the temporary storage location of downloaded container images. Podman defaults to use `/var/tmp`.
 
+#### **--transient-store**
+
+Enables a global transient storaga mode where all container metadata is stored on non-persistant media (i.e. in the location specified by `--runroot`).
+This mode allows starting containers faster, as well as guaranteeing a fresh state on boot in case of unclean shutdowns or other problems. However
+it is not compabible with a traditional model where containers persist across reboots.
+
+Default value for this is configured in `/etc/containers/storage.conf`.
+
 #### **--url**=*value*
 URL to access Podman service (default from `containers.conf`, rootless `unix://run/user/$UID/podman/podman.sock` or as root `unix://run/podman/podman.sock`).
 Setting this option will switch the **--remote** option to true.

libpod/define/info.go

@@ -118,6 +118,7 @@ type StoreInfo struct {
 	ImageStore      ImageStore        `json:"imageStore"`
 	RunRoot         string            `json:"runRoot"`
 	VolumePath      string            `json:"volumePath"`
+	TransientStore  bool              `json:"transientStore"`
 }
 
 // ImageStore describes the image store.  Right now only the number

libpod/info.go

@@ -226,6 +226,7 @@ func (r *Runtime) storeInfo() (*define.StoreInfo, error) {
 		GraphOptions:       nil,
 		VolumePath:         r.config.Engine.VolumePath,
 		ConfigFile:         configFile,
+		TransientStore:     r.store.TransientStore(),
 	}
 
 	graphOptions := map[string]interface{}{}

libpod/options.go

@@ -109,6 +109,18 @@ func WithStorageConfig(config storage.StoreOptions) RuntimeOption {
 	}
 }
 
+func WithTransientStore(transientStore bool) RuntimeOption {
+	return func(rt *Runtime) error {
+		if rt.valid {
+			return define.ErrRuntimeFinalized
+		}
+
+		rt.storageConfig.TransientStore = transientStore
+
+		return nil
+	}
+}
+
 // WithSignaturePolicy specifies the path of a file which decides how trust is
 // managed for images we've pulled.
 // If this is not specified, the system default configuration will be used

libpod/runtime.go

@@ -396,6 +396,7 @@ func makeRuntime(runtime *Runtime) (retErr error) {
 	logrus.Debugf("Using static dir %s", runtime.config.Engine.StaticDir)
 	logrus.Debugf("Using tmp dir %s", runtime.config.Engine.TmpDir)
 	logrus.Debugf("Using volume path %s", runtime.config.Engine.VolumePath)
+	logrus.Debugf("Using transient store: %v", runtime.storageConfig.TransientStore)
 
 	// Validate our config against the database, now that we've set our
 	// final storage configuration

pkg/domain/entities/engine.go

@@ -55,4 +55,5 @@ type PodmanConfig struct {
 	StorageOpts    []string
 	SSHMode        string
 	MachineMode    bool
+	TransientStore bool
 }

pkg/domain/infra/runtime_libpod.go

@@ -171,6 +171,9 @@ func getRuntime(ctx context.Context, fs *flag.FlagSet, opts *engineOpts) (*libpo
 			storageOpts.GraphDriverOptions = cfg.StorageOpts
 		}
 	}
+	if fs.Changed("transient-store") {
+		options = append(options, libpod.WithTransientStore(cfg.TransientStore))
+	}
 	if opts.migrate {
 		options = append(options, libpod.WithMigrate())
 		if opts.name != "" {

pkg/specgenutil/util.go

@@ -282,6 +282,7 @@ func CreateExitCommandArgs(storageConfig storageTypes.StoreOptions, config *conf
 		"--network-config-dir", config.Network.NetworkConfigDir,
 		"--network-backend", config.Network.NetworkBackend,
 		"--volumepath", config.Engine.VolumePath,
+		fmt.Sprintf("--transient-store=%t", storageConfig.TransientStore),
 	}
 	if config.Engine.OCIRuntime != "" {
 		command = append(command, []string{"--runtime", config.Engine.OCIRuntime}...)