run with pidfile option

README.md

@@ -328,6 +328,7 @@ Metadata flags:
 - :whale: `-l, --label`: Set meta data on a container
 - :whale: `--label-file`: Read in a line delimited file of labels
 - :whale: `--cidfile`: Write the container ID to the file
+- :nerd_face: `--pidfile`: file path to write the task's pid. The CLI syntax conforms to Podman convention.
 
 Shared memory flags:
 - :whale: `--shm-size`: Size of `/dev/shm`

cmd/nerdctl/run.go

@@ -255,6 +255,10 @@ var runCommand = &cli.Command{
 			Name:  "shm-size",
 			Usage: "Size of /dev/shm",
 		},
+		&cli.StringFlag{
+			Name:  "pidfile",
+			Usage: "file path to write the task's pid",
+		},
 	},
 }
 
@@ -526,7 +530,13 @@ func runAction(clicontext *cli.Context) error {
 			return err
 		}
 	}
-	ilOpt, err := withInternalLabels(ns, name, hostname, stateDir, netSlice, ports, logURI, anonVolumes)
+
+	var pidFile string
+	if clicontext.IsSet("pidfile") {
+		pidFile = clicontext.String("pidfile")
+	}
+
+	ilOpt, err := withInternalLabels(ns, name, hostname, stateDir, netSlice, ports, logURI, anonVolumes, pidFile)
 	if err != nil {
 		return err
 	}
@@ -589,9 +599,11 @@ func runAction(clicontext *cli.Context) error {
 			return err
 		}
 	}
+
 	if err := task.Start(ctx); err != nil {
 		return err
 	}
+
 	if flagD {
 		fmt.Fprintf(clicontext.App.Writer, "%s\n", id)
 		return nil
@@ -800,7 +812,7 @@ func withContainerLabels(clicontext *cli.Context) ([]containerd.NewContainerOpts
 	return []containerd.NewContainerOpts{o}, nil
 }
 
-func withInternalLabels(ns, name, hostname, containerStateDir string, networks []string, ports []gocni.PortMapping, logURI string, anonVolumes []string) (containerd.NewContainerOpts, error) {
+func withInternalLabels(ns, name, hostname, containerStateDir string, networks []string, ports []gocni.PortMapping, logURI string, anonVolumes []string, pidFile string) (containerd.NewContainerOpts, error) {
 	m := make(map[string]string)
 	m[labels.Namespace] = ns
 	if name != "" {
@@ -830,6 +842,11 @@ func withInternalLabels(ns, name, hostname, containerStateDir string, networks [
 		}
 		m[labels.AnonymousVolumes] = string(anonVolumeJSON)
 	}
+
+	if pidFile != "" {
+		m[labels.PIDFile] = pidFile
+	}
+
 	return containerd.WithAdditionalContainerLabels(m), nil
 }
 

pkg/labels/labels.go

@@ -57,6 +57,10 @@ const (
 	// LogURI is the log URI
 	LogURI = Prefix + "log-uri"
 
+	// PIDFile is the `nerdctl run --pidfile`
+	// (CLI flag is "pidfile", not "pid-file", for Podman compatibility)
+	PIDFile = Prefix + "pid-file"
+
 	// AnonymousVolumes is a JSON-marshalled string of []string
 	AnonymousVolumes = Prefix + "anonymous-volumes"
 )

pkg/ocihook/ocihook.go

@@ -25,6 +25,8 @@ import (
 	"os"
 	"path/filepath"
 
+	"github.com/containerd/containerd/cmd/ctr/commands"
+
 	pkgapparmor "github.com/containerd/containerd/pkg/apparmor"
 	gocni "github.com/containerd/go-cni"
 	"github.com/containerd/nerdctl/pkg/dnsutil/hostsstore"
@@ -150,6 +152,12 @@ func newHandlerOpts(state *specs.State, dataStore, cniPath, cniNetconfPath strin
 		return nil, errors.Errorf("unexpected network type %v", netType)
 	}
 
+	if pidFile := o.state.Annotations[labels.PIDFile]; pidFile != "" {
+		if err := commands.WritePidFile(pidFile, state.Pid); err != nil {
+			return nil, err
+		}
+	}
+
 	if portsJSON := o.state.Annotations[labels.Ports]; portsJSON != "" {
 		if err := json.Unmarshal([]byte(portsJSON), &o.ports); err != nil {
 			return nil, err