Improve error handling in runc

The error handling on the runc cli is currenly pretty messy because
messages to the user are split between regular stderr format and logrus
message format.  This changes all the error reporting to the cli to only
output on stderr and exit(1) for consumers of the api.

By default logrus logs to /dev/null so that it is not seen by the user.
If the user wants extra and/or structured loggging/errors from runc they
can use the `--log` flag to provide a path to the file where they want
this information.  This allows a consistent behavior on the cli but
extra power and information when debugging with logs.

This also includes a change to enable the same logging information
inside the container's init by adding an init cli command that can share
the existing flags for all other runc commands.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

events.go

@@ -35,7 +35,7 @@ information is displayed once every 5 seconds.`,
 	Action: func(context *cli.Context) {
 		container, err := getContainer(context)
 		if err != nil {
-			logrus.Fatal(err)
+			fatal(err)
 		}
 		var (
 			stats  = make(chan *libcontainer.Stats, 1)
@@ -74,7 +74,7 @@ information is displayed once every 5 seconds.`,
 		}()
 		n, err := container.NotifyOOM()
 		if err != nil {
-			logrus.Fatal(err)
+			fatal(err)
 		}
 		for {
 			select {

exec.go

@@ -9,7 +9,6 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/Sirupsen/logrus"
 	"github.com/codegangsta/cli"
 	"github.com/opencontainers/specs"
 )
@@ -80,11 +79,11 @@ following will output a list of processes running in the container:
 	},
 	Action: func(context *cli.Context) {
 		if os.Geteuid() != 0 {
-			logrus.Fatal("runc should be run as root")
+			fatalf("runc should be run as root")
 		}
 		status, err := execProcess(context)
 		if err != nil {
-			logrus.Fatalf("exec failed: %v", err)
+			fatalf("exec failed: %v", err)
 		}
 		os.Exit(status)
 	},

main.go

@@ -49,6 +49,7 @@ func main() {
 		},
 		cli.StringFlag{
 			Name:  "log",
+			Value: "/dev/null",
 			Usage: "set the log file path where internal debug information is written",
 		},
 		cli.StringFlag{
@@ -72,6 +73,7 @@ func main() {
 		deleteCommand,
 		eventsCommand,
 		execCommand,
+		initCommand,
 		killCommand,
 		listCommand,
 		pauseCommand,
@@ -86,7 +88,7 @@ func main() {
 			logrus.SetLevel(logrus.DebugLevel)
 		}
 		if path := context.GlobalString("log"); path != "" {
-			f, err := os.Create(path)
+			f, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
 			if err != nil {
 				return err
 			}
@@ -103,6 +105,6 @@ func main() {
 		return nil
 	}
 	if err := app.Run(os.Args); err != nil {
-		logrus.Fatal(err)
+		fatal(err)
 	}
 }

main_unsupported.go

@@ -2,10 +2,7 @@
 
 package main
 
-import (
+import "github.com/codegangsta/cli"
-	"github.com/Sirupsen/logrus"
-	"github.com/codegangsta/cli"
-)
 
 var (
 	checkpointCommand cli.Command
@@ -16,5 +13,5 @@ var (
 )
 
 func runAction(*cli.Context) {
-	logrus.Fatal("Current OS is not supported yet")
+	fatalf("Current OS is not supported yet")
 }

restore.go

@@ -3,7 +3,6 @@
 package main
 
 import (
-	"fmt"
 	"os"
 	"syscall"
 
@@ -124,7 +123,7 @@ func restoreContainer(context *cli.Context, spec *specs.LinuxSpec, config *confi
 		logrus.Error(err)
 	}
 	if status == libcontainer.Running {
-		fatal(fmt.Errorf("Container with id %s already running", id))
+		fatalf("Container with id %s already running", id)
 	}
 
 	setManageCgroupsMode(context, options)

spec.go

@@ -13,7 +13,6 @@ import (
 	"strings"
 	"syscall"
 
-	"github.com/Sirupsen/logrus"
 	"github.com/codegangsta/cli"
 	"github.com/opencontainers/runc/libcontainer/cgroups"
 	"github.com/opencontainers/runc/libcontainer/configs"
@@ -163,14 +162,14 @@ var specCommand = cli.Command{
 			}
 		}
 		if err := checkNoFile(specConfig); err != nil {
-			logrus.Fatal(err)
+			fatal(err)
 		}
 		data, err := json.MarshalIndent(&spec, "", "\t")
 		if err != nil {
-			logrus.Fatal(err)
+			fatal(err)
 		}
 		if err := ioutil.WriteFile(specConfig, data, 0666); err != nil {
-			logrus.Fatal(err)
+			fatal(err)
 		}
 	},
 }

start.go

@@ -6,7 +6,6 @@ import (
 	"os"
 	"runtime"
 
-	"github.com/Sirupsen/logrus"
 	"github.com/codegangsta/cli"
 	"github.com/coreos/go-systemd/activation"
 	"github.com/opencontainers/runc/libcontainer"
@@ -63,12 +62,12 @@ is a directory with a specification file and a root filesystem.`,
 		}
 
 		if os.Geteuid() != 0 {
-			logrus.Fatal("runc should be run as root")
+			fatalf("runc should be run as root")
 		}
 
 		status, err := startContainer(context, spec)
 		if err != nil {
-			logrus.Fatalf("Container start failed: %v", err)
+			fatalf("Container start failed: %v", err)
 		}
 		// exit with the container's exit status so any external supervisor is
 		// notified of the exit with the correct exit status.
@@ -76,8 +75,12 @@ is a directory with a specification file and a root filesystem.`,
 	},
 }
 
-func init() {
+var initCommand = cli.Command{
-	if len(os.Args) > 1 && os.Args[1] == "init" {
+	Name: "init",
+	Usage: `init is used to initialize the containers namespaces and launch the users process.
+    This command should not be called outside of runc.
+    `,
+	Action: func(context *cli.Context) {
 		runtime.GOMAXPROCS(1)
 		runtime.LockOSThread()
 		factory, _ := libcontainer.New("")
@@ -85,7 +88,7 @@ func init() {
 			fatal(err)
 		}
 		panic("libcontainer: container init failed to exec")
-	}
+	},
 }
 
 func startContainer(context *cli.Context, spec *specs.LinuxSpec) (int, error) {

utils.go

@@ -152,15 +152,31 @@ func containerPreload(context *cli.Context) error {
 
 // loadFactory returns the configured factory instance for execing containers.
 func loadFactory(context *cli.Context) (libcontainer.Factory, error) {
-	root := context.GlobalString("root")
+	var (
+		debug = "false"
+		root  = context.GlobalString("root")
+	)
+	if context.GlobalBool("debug") {
+		debug = "true"
+	}
 	abs, err := filepath.Abs(root)
 	if err != nil {
 		return nil, err
 	}
+	logAbs, err := filepath.Abs(context.GlobalString("log"))
+	if err != nil {
+		return nil, err
+	}
 	return libcontainer.New(abs, libcontainer.Cgroupfs, func(l *libcontainer.LinuxFactory) error {
 		l.CriuPath = context.GlobalString("criu")
 		return nil
-	})
+	},
+		libcontainer.InitArgs(os.Args[0],
+			"--log", logAbs,
+			"--log-format", context.GlobalString("log-format"),
+			fmt.Sprintf("--debug=%s", debug),
+			"init"),
+	)
 }
 
 // getContainer returns the specified container instance by loading it from state
@@ -180,6 +196,8 @@ func getContainer(context *cli.Context) (libcontainer.Container, error) {
 // fatal prints the error's details if it is a libcontainer specific error type
 // then exits the program with an exit status of 1.
 func fatal(err error) {
+	// make sure the error is written to the logger
+	logrus.Error(err)
 	// return proper unix error codes
 	if exerr, ok := err.(*exec.Error); ok {
 		switch exerr.Err {
@@ -196,14 +214,14 @@ func fatal(err error) {
 			}
 		}
 	}
-	if lerr, ok := err.(libcontainer.Error); ok {
-		lerr.Detail(os.Stderr)
-		os.Exit(1)
-	}
 	fmt.Fprintln(os.Stderr, err)
 	os.Exit(1)
 }
 
+func fatalf(t string, v ...interface{}) {
+	fatal(fmt.Errorf(t, v...))
+}
+
 func getDefaultImagePath(context *cli.Context) string {
 	cwd, err := os.Getwd()
 	if err != nil {