fix: write runtime PID file when provided

Ensure the PID is written to the runtime-provided --pid-file after
container creation. This allows supervisors like conmon to track and
reap the container process correctly, preventing early cleanup or EOF
failures. This change also ensures that Podman can reliably start urunc
containers.

Signed-off-by: sidneychang <2190206983@qq.com>

Author: sidneychang

cmd/urunc/create.go

@@ -258,6 +258,13 @@ func createUnikontainer(cmd *cli.Command, uruncCfg *unikontainers.UruncConfig) (
 	if err != nil {
 		return err
 	}
+	// OCI runtimes are expected to write the PID to the provided pid-file.
+	// Without it, the supervising runtime cannot track/reap the process and cleanup may fail.
+	if pidFile := cmd.String("pid-file"); pidFile != "" {
+		if err := unikontainers.WritePidFile(pidFile, containerPid); err != nil {
+			return err
+		}
+	}
 
 	// execute CreateRuntime hooks
 	err = unikontainer.ExecuteHooks("CreateRuntime")

pkg/unikontainers/utils.go

@@ -131,6 +131,11 @@ func loadSpec(bundleDir string) (*specs.Spec, error) {
 	return &spec, nil
 }
 
+// WritePidFile is a public wrapper used by cmd to satisfy OCI pid-file expectations.
+func WritePidFile(path string, pid int) error {
+	return writePidFile(path, pid)
+}
+
 // writePidFile writes the content of pid to the file defined by path
 func writePidFile(path string, pid int) error {
 	var (