Added wwctl container exec ... feature

internal/app/wwctl/container/exec/main.go

@@ -0,0 +1,40 @@
+// +build linux
+
+package exec
+
+import (
+	"fmt"
+	"github.com/hpcng/warewulf/internal/pkg/container"
+	"github.com/hpcng/warewulf/internal/pkg/wwlog"
+	"github.com/spf13/cobra"
+	"os"
+	"os/exec"
+	"syscall"
+)
+
+func CobraRunE(cmd *cobra.Command, args []string) error {
+
+	containerName := args[0]
+
+	if container.ValidSource(containerName) == false {
+		wwlog.Printf(wwlog.ERROR, "Unknown Warewulf container: %s\n", containerName)
+		os.Exit(1)
+	}
+
+	c := exec.Command("/proc/self/exe", append([]string{"container", "exec", "__child"}, args...)...)
+
+	//c := exec.Command("/bin/sh")
+	c.SysProcAttr = &syscall.SysProcAttr{
+		Cloneflags: syscall.CLONE_NEWUTS | syscall.CLONE_NEWPID | syscall.CLONE_NEWNS,
+	}
+	c.Stdin = os.Stdin
+	c.Stdout = os.Stdout
+	c.Stderr = os.Stderr
+
+	if err := c.Run(); err != nil {
+		fmt.Println("ERROR", err)
+		os.Exit(1)
+	}
+
+	return nil
+}