Add basic logic needed to correctly mount the VHD when initializing a server.

internal/vhd/vhd.go

@@ -43,6 +43,7 @@ type CfgOption func(d *Disk) *Disk
 
 // Disk represents the underlying virtual disk for the instance.
 type Disk struct {
+	// The total size of the disk allowed in bytes.
 	size      int64
 	diskPath  string
 	mountAt   string
@@ -51,8 +52,8 @@ type Disk struct {
 }
 
 // New returns a new Disk instance. The "size" parameter should be provided in
-// megabytes of space allowed for the disk. An additional slice of option
-// callbacks can be provided to programatically swap out the underlying filesystem
+// bytes of space allowed for the disk. An additional slice of option callbacks
+// can be provided to programatically swap out the underlying filesystem
 // implementation or the underlying command exection engine.
 func New(size int64, diskPath string, mountAt string, opts ...func(*Disk)) *Disk {
 	if diskPath == "" || mountAt == "" {
@@ -181,7 +182,10 @@ func (d *Disk) Allocate(ctx context.Context) error {
 	} else if err != nil {
 		return errors.Wrap(err, "vhd: failed to check for existence of root disk")
 	}
-	cmd := d.commander(ctx, "fallocate", "-l", fmt.Sprintf("%dM", d.size), d.diskPath)
+	// We use 1024 as the multiplier for all of the disk space logic within the
+	// application. Passing "K" (/1024) is the same as "KiB" for fallocate, but
+	// is different than "KB" (/1000).
+	cmd := d.commander(ctx, "fallocate", "-l", fmt.Sprintf("%dK", d.size / 1024), d.diskPath)
 	if _, err := cmd.Output(); err != nil {
 		msg := "vhd: failed to execute fallocate command"
 		if v, ok := err.(*exec.ExitError); ok {

internal/vhd/vhd_test.go

@@ -62,14 +62,14 @@ func newMockDisk(c CommanderProvider) *Disk {
 	if c != nil {
 		w = c
 	}
-	return New(100, "/foo", "/bar", WithFs(afero.NewMemMapFs()), WithCommander(w))
+	return New(100 * 1024 * 1024, "/foo", "/bar", WithFs(afero.NewMemMapFs()), WithCommander(w))
 }
 
 func Test_New(t *testing.T) {
 	t.Run("creates expected struct", func(t *testing.T) {
-		d := New(100, "/foo", "/bar")
+		d := New(100 * 1024 * 1024, "/foo", "/bar")
 		assert.NotNil(t, d)
-		assert.Equal(t, int64(100), d.size)
+		assert.Equal(t, int64(100 * 1024 * 1024), d.size)
 		assert.Equal(t, "/foo", d.diskPath)
 		assert.Equal(t, "/bar", d.mountAt)
 
@@ -360,7 +360,7 @@ func TestDisk_Allocate(t *testing.T) {
 				output: func() ([]byte, error) {
 					called = true
 					assert.Equal(t, "fallocate", name)
-					assert.Equal(t, []string{"-l", "100M", "/foo"}, args)
+					assert.Equal(t, []string{"-l", "102400K", "/foo"}, args)
 					return nil, nil
 				},
 			}