From 28d012ea007b3146cc7542277a097c8adc5504fd Mon Sep 17 00:00:00 2001
From: Vincent Batts <vbatts@hashbangbash.com>
Date: Tue, 4 Apr 2017 15:57:35 -0400
Subject: [PATCH 1/2] containerd: add access to default config

when wanting to craft a custom config, but based on the default config,
add a route to output the containerd config to a tempfile.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>
---
 cmd/containerd/config.go | 16 +++++++++++++++-
 cmd/containerd/main.go   | 16 +++++++++++++++-
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/cmd/containerd/config.go b/cmd/containerd/config.go
index 65e4018..82187f7 100644
--- a/cmd/containerd/config.go
+++ b/cmd/containerd/config.go
@@ -1,6 +1,11 @@
 package main
 
-import "github.com/BurntSushi/toml"
+import (
+	"bytes"
+	"io"
+
+	"github.com/BurntSushi/toml"
+)
 
 func defaultConfig() *config {
 	return &config{
@@ -58,6 +63,15 @@ func (c *config) decodePlugin(name string, v interface{}) error {
 	return c.md.PrimitiveDecode(p, v)
 }
 
+func (c *config) WriteTo(w io.Writer) (int64, error) {
+	buf := bytes.NewBuffer(nil)
+	e := toml.NewEncoder(buf)
+	if err := e.Encode(c); err != nil {
+		return 0, err
+	}
+	return io.Copy(w, buf)
+}
+
 type grpcConfig struct {
 	Socket string `toml:"socket"`
 	Uid    int    `toml:"uid"`
diff --git a/cmd/containerd/main.go b/cmd/containerd/main.go
index fa0bffd..f9b5f5c 100644
--- a/cmd/containerd/main.go
+++ b/cmd/containerd/main.go
@@ -3,6 +3,7 @@ package main
 import (
 	_ "expvar"
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	_ "net/http/pprof"
 	"os"
@@ -60,7 +61,7 @@ func main() {
 	app.Flags = []cli.Flag{
 		cli.StringFlag{
 			Name:  "config,c",
-			Usage: "path to the configuration file",
+			Usage: "path to the configuration file (Use 'default' to output the default toml)",
 			Value: "/etc/containerd/config.toml",
 		},
 		cli.StringFlag{
@@ -148,6 +149,19 @@ func main() {
 }
 
 func before(context *cli.Context) error {
+	if context.GlobalString("config") == "default" {
+		fh, err := ioutil.TempFile("", "containerd-config.toml.")
+		if err != nil {
+			return err
+		}
+		if _, err := conf.WriteTo(fh); err != nil {
+			fh.Close()
+			return err
+		}
+		fh.Close()
+		log.G(global).Infof("containerd default config written to %q", fh.Name())
+		os.Exit(0)
+	}
 	if err := loadConfig(context.GlobalString("config")); err != nil &&
 		!os.IsNotExist(err) {
 		return err

From 93417d446c82626ebdf59014b109086cd24a8304 Mon Sep 17 00:00:00 2001
From: Vincent Batts <vbatts@hashbangbash.com>
Date: Tue, 4 Apr 2017 15:31:35 -0400
Subject: [PATCH 2/2] containerd: missing config creates a default

This fixes silently ignore the config file not existing as well.

```bash
sudo ./bin/containerd --config farts
$ sudo ./bin/containerd --config farts
INFO[0000] config "farts" does not exist. Creating it.   module=containerd
INFO[0000] starting containerd boot...                   module=containerd
INFO[0000] starting debug API...                         debug="/run/containerd/debug.sock" module=containerd
INFO[0000] loading monitor plugin "cgroups"...           module=containerd
INFO[0000] loading runtime plugin "linux"...             module=containerd
INFO[0000] loading snapshot plugin "snapshot-overlay"...  module=containerd
INFO[0000] loading grpc service plugin "content-grpc"...  module=containerd
INFO[0000] loading grpc service plugin "metrics-grpc"...  module=containerd
INFO[0000] loading grpc service plugin "runtime-grpc"...  module=containerd
INFO[0000] loading grpc service plugin "healthcheck-grpc"...  module=containerd
INFO[0000] loading grpc service plugin "rootfs-grpc"...  module=containerd
INFO[0000] starting GRPC API server...                   module=containerd
INFO[0000] containerd successfully booted in 0.001465s   module=containerd
^C$ cat farts
state = "/run/containerd"
root = "/var/lib/containerd"
snapshotter = "overlay"
subreaper = false

[grpc]
  socket = "/run/containerd/containerd.sock"
  uid = 0
  gid = 0

[debug]
  socket = "/run/containerd/debug.sock"
  level = "info"

[metrics]
  address = ""
```

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>
---
 cmd/containerd/main.go | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/cmd/containerd/main.go b/cmd/containerd/main.go
index f9b5f5c..2a4135c 100644
--- a/cmd/containerd/main.go
+++ b/cmd/containerd/main.go
@@ -162,10 +162,22 @@ func before(context *cli.Context) error {
 		log.G(global).Infof("containerd default config written to %q", fh.Name())
 		os.Exit(0)
 	}
-	if err := loadConfig(context.GlobalString("config")); err != nil &&
-		!os.IsNotExist(err) {
+	err := loadConfig(context.GlobalString("config"))
+	if err != nil && !os.IsNotExist(err) {
 		return err
+	} else if err != nil && os.IsNotExist(err) {
+		log.G(global).Infof("config %q does not exist. Creating it.", context.GlobalString("config"))
+		fh, err := os.Create(context.GlobalString("config"))
+		if err != nil {
+			return err
+		}
+		if _, err := conf.WriteTo(fh); err != nil {
+			fh.Close()
+			return err
+		}
+		fh.Close()
 	}
+
 	// the order for config vs flag values is that flags will always override
 	// the config values if they are set
 	if err := setLevel(context); err != nil {