fix for alpine's simpler blkid cmd

Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au>

util/util_linux.go

@@ -3,10 +3,15 @@
 package util
 
 import (
+	"bufio"
+	"bytes"
 	"os"
+	"os/exec"
+	"strings"
 	"syscall"
 
 	"github.com/docker/docker/pkg/mount"
+	"github.com/rancher/os/log"
 )
 
 func mountProc() error {
@@ -43,3 +48,32 @@ func Mount(device, directory, fsType, options string) error {
 func Unmount(target string) error {
 	return mount.Unmount(target)
 }
+
+func Blkid(label string) (deviceName, deviceType string) {
+	// Not all blkid's have `blkid -L label (see busybox/alpine)
+	cmd := exec.Command("blkid")
+	cmd.Stderr = os.Stderr
+	out, err := cmd.Output()
+	if err != nil {
+		log.Errorf("Failed to run blkid: %s", err)
+		return
+	}
+	r := bytes.NewReader(out)
+	s := bufio.NewScanner(r)
+	for s.Scan() {
+		line := s.Text()
+		log.Debugf("blkid: %s", cmd, line)
+		if !strings.Contains(line, `LABEL="`+label+`"`) {
+			continue
+		}
+		d := strings.Split(line, ":")
+		deviceName = d[0]
+
+		s1 := strings.Split(line, `TYPE="`)
+		s2 := strings.Split(s1[1], `"`)
+		deviceType = s2[0]
+		log.Debugf("blkid type of %s: %s", deviceName, deviceType)
+		return
+	}
+	return
+}