Verify FS availability

Author: ashald

Vagrantfile

@@ -1,5 +1,5 @@
 Vagrant.configure(2) do |config|
   config.vm.box = "ubuntu/trusty64"
   config.vm.provision :docker
-  config.vm.provision "shell", inline: "apt update && apt install -y jq xfsprogs"
+  config.vm.provision "shell", inline: "apt-get update && apt-get install -y jq xfsprogs"
 end

main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"os"
+	"os/exec"
 
 	"github.com/alexflint/go-arg"
 	"github.com/rs/zerolog"
@@ -11,11 +12,8 @@ import (
 	v "github.com/docker/go-plugins-helpers/volume"
 )
 
-const (
-	socketAddress = "/run/docker/plugins/docker-volume-loopback.sock"
-)
-
 type config struct {
+	Socket      string `arg:"--socket,env:SOCKET,help:path to the plugin UNIX socket under /run/docker/plugins/"`
 	StateDir    string `arg:"--state-dir,env:STATE_DIR,help:dir used to keep track of currently mounted volumes"`
 	DataDir     string `arg:"--data-dir,env:DATA_DIR,help:dir used to store actual volume data"`
 	MountDir    string `arg:"--mount-dir,env:MOUNT_DIR,help:dir used to create mount-points"`
@@ -26,6 +24,7 @@ type config struct {
 var (
 	logger = zerolog.New(os.Stdout)
 	args   = &config{
+		Socket:      "/run/docker/plugins/docker-volume-loopback.sock",
 		StateDir:    "/run/docker-volume-loopback",
 		DataDir:     "/var/lib/docker-volume-loopback",
 		MountDir:    "/mnt",
@@ -37,16 +36,35 @@ var (
 func main() {
 	arg.MustParse(args)
 
+	if args.Debug {
+		zerolog.SetGlobalLevel(zerolog.DebugLevel)
+	}
+
 	logger.Info().
-		Str("socket-address", socketAddress).
+		Str("socket-address", args.Socket).
 		Interface("args", args).
 		Msg("initializing plugin")
 
-	if args.Debug {
-		zerolog.SetGlobalLevel(zerolog.DebugLevel)
+	_, errXfs := exec.LookPath("mkfs.xfs")
+	if errXfs != nil {
+		logger.Warn().
+			Err(errXfs).
+			Msg("mkfs.xfs is not available, please install 'xfsprogs' to be able to use xfs filesystem")
+	}
+
+	_, errExt4 := exec.LookPath("mkfs.ext4")
+	if errExt4 != nil {
+		logger.Warn().
+			Err(errExt4).
+			Msg("mkfs.ext4 is not available, please install 'e2fsprogs' to be able to use ext4 filesystem")
+	}
+	if errXfs != nil && errExt4 != nil {
+		logger.Fatal().
+			Msg("Neither of supported filesystems (xfs, ext4) are available")
+		os.Exit(1)
 	}
 
-	d, err := driver.NewDriver(driver.Config{
+	driverInstance, err := driver.NewDriver(driver.Config{
 		StateDir:    args.StateDir,
 		DataDir:     args.DataDir,
 		MountDir:    args.MountDir,
@@ -55,16 +73,16 @@ func main() {
 	if err != nil {
 		logger.Fatal().
 			Err(err).
-			Msg("failed to initialize loopback volume driver")
+			Msg("failed to initialize 'docker-volume-loopback' driver")
 		os.Exit(1)
 	}
 
-	h := v.NewHandler(d)
-	err = h.ServeUnix(socketAddress, 0)
+	handler := v.NewHandler(driverInstance)
+	err = handler.ServeUnix(args.Socket, 0)
 	if err != nil {
 		logger.Fatal().
 			Err(err).
-			Str("socket-address", socketAddress).
+			Str("socket-address", args.Socket).
 			Msg("failed to server volume plugin api over unix socket")
 		os.Exit(1)
 	}

plugin/config.json

@@ -28,10 +28,16 @@
             "Name": "DEFAULT_SIZE",
             "Settable": ["value"],
             "Value": "1GiB"
+        },
+        {
+            "Description": "Path to the plugin UNIX socket",
+            "Name": "SOCKET",
+            "Settable": [],
+            "Value": "/run/docker/plugins/docker-volume-loop.sock"
         }
     ],
     "Interface": {
-        "Socket": "docker-volume-loopback.sock",
+        "Socket": "docker-volume-loop.sock",
         "Types": ["docker.volumedriver/1.0"]
     },
     "Linux": {