Add ipc docs

Signed-off-by: Min Uk Lee <[email protected]>

Author: minuk-dev

docs/command-reference.md

@@ -351,7 +351,7 @@ Logging flags:
 
 Shared memory flags:
 
-- :whale: `--ipc`: IPC namespace to use
+- :whale: `--ipc=(host|private|shareable|container:<container>)`: IPC namespace to use and mount `/dev/shm`. Default: "private". Only implemented on Linux.
 - :whale: `--shm-size`: Size of `/dev/shm`
 
 GPU flags:

pkg/cmd/container/run_linux.go

@@ -163,7 +163,7 @@ func generateNamespaceOpts(
 func generateIPCOpts(ctx context.Context, client *containerd.Client, ipcFlag string, shmSize string, stateDir string) ([]oci.SpecOpts, string, error) {
 	ipcFlag = strings.ToLower(ipcFlag)
 
-	ipc, err := ipcutil.Detect(ctx, client, stateDir, ipcFlag, shmSize)
+	ipc, err := ipcutil.DetectFlags(ctx, client, stateDir, ipcFlag, shmSize)
 	if err != nil {
 		return nil, "", err
 	}

pkg/ipcutil/ipcutil.go

@@ -44,6 +44,8 @@ type IPC struct {
 	// HostShmPath is only used when mode is shareable
 	HostShmPath *string `json:"host_shm_path,omitempty"`
 
+	// ShmSize is only used when mode is private or shareable
+	// Devshm size in bytes
 	ShmSize string `json:"shm_size,omitempty"`
 }
 
@@ -54,7 +56,9 @@ const (
 	Container IPCMode = "container"
 )
 
-func Detect(ctx context.Context, client *containerd.Client, stateDir string, ipc string, shmSize string) (IPC, error) {
+// DetectFlags detects IPC mode from the given ipc string and shmSize string.
+// If ipc is empty, it returns IPC{Mode: Private}.
+func DetectFlags(ctx context.Context, client *containerd.Client, stateDir string, ipc string, shmSize string) (IPC, error) {
 	var res IPC
 	res.ShmSize = shmSize
 	switch ipc {
@@ -98,6 +102,7 @@ func Detect(ctx context.Context, client *containerd.Client, stateDir string, ipc
 	return res, nil
 }
 
+// EncodeIPCLabel encodes IPC spec into a label.
 func EncodeIPCLabel(ipc IPC) (string, error) {
 	if ipc.Mode == "" {
 		return "", nil
@@ -109,6 +114,8 @@ func EncodeIPCLabel(ipc IPC) (string, error) {
 	return string(b), nil
 }
 
+// DecodeIPCLabel decodes IPC spec from a label.
+// For backward compatibility, if ipcLabel is empty, it returns IPC{Mode: Private}.
 func DecodeIPCLabel(ipcLabel string) (IPC, error) {
 	if ipcLabel == "" {
 		return IPC{
@@ -123,6 +130,7 @@ func DecodeIPCLabel(ipcLabel string) (IPC, error) {
 	return ipc, nil
 }
 
+// GenerateIPCOpts generates IPC spec opts from the given IPC.
 func GenerateIPCOpts(ctx context.Context, ipc IPC, client *containerd.Client) ([]oci.SpecOpts, error) {
 	opts := make([]oci.SpecOpts, 0)
 
@@ -199,6 +207,7 @@ func GenerateIPCOpts(ctx context.Context, ipc IPC, client *containerd.Client) ([
 	return opts, nil
 }
 
+// WithBindMountHostOtherSourceIPC replaces /dev/shm mount with rbind by the given path on host
 func withBindMountHostOtherSourceIPC(source string) oci.SpecOpts {
 	return func(_ context.Context, _ oci.Client, _ *containers.Container, s *oci.Spec) error {
 		for i, m := range s.Mounts {