Merge pull request #320 from Itxaka/drop_blkid_block

Use udev for partition UUID

README.md

@@ -546,8 +546,10 @@ Each `ghw.Partition` struct contains these fields:
 * `ghw.Partition.Disk` is a pointer to the `ghw.Disk` object associated with
   the partition. This will be `nil` if the `ghw.Partition` struct was returned
   by the `ghw.DiskPartitions()` library function.
-* `ghw.Partition.UUID` is a string containing the volume UUID on Linux, the
-  partition UUID on MacOS and nothing on Windows.
+* `ghw.Partition.UUID` is a string containing the partition UUID on Linux, the
+  partition UUID on MacOS and nothing on Windows. On Linux
+  systems, this is derived from the `ID_PART_ENTRY_UUID` udev entry for the
+  partition.
 
 ```go
 package main

pkg/block/block_linux.go

@@ -10,7 +10,6 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -209,7 +208,7 @@ func diskPartitions(ctx *context.Context, paths *linuxpath.Paths, disk string) [
 		}
 		size := partitionSizeBytes(paths, disk, fname)
 		mp, pt, ro := partitionInfo(paths, fname)
-		du := diskPartUUID(ctx, fname)
+		du := diskPartUUID(paths, disk, fname)
 		label := diskPartLabel(paths, disk, fname)
 		if pt == "" {
 			pt = diskPartTypeUdev(paths, disk, fname)
@@ -268,37 +267,16 @@ func diskPartTypeUdev(paths *linuxpath.Paths, disk string, partition string) str
 	return util.UNKNOWN
 }
 
-func diskPartUUID(ctx *context.Context, part string) string {
-	if !ctx.EnableTools {
-		ctx.Warn("EnableTools=false disables partition UUID detection.")
-		return ""
-	}
-	if !strings.HasPrefix(part, "/dev") {
-		part = "/dev/" + part
-	}
-	args := []string{
-		"blkid",
-		"-s",
-		"PARTUUID",
-		part,
-	}
-	out, err := exec.Command(args[0], args[1:]...).Output()
+func diskPartUUID(paths *linuxpath.Paths, disk string, partition string) string {
+	info, err := udevInfoPartition(paths, disk, partition)
 	if err != nil {
-		ctx.Warn("failed to read disk partuuid of %s : %s\n", part, err.Error())
-		return ""
-	}
-
-	if len(out) == 0 {
-		return ""
+		return util.UNKNOWN
 	}
 
-	parts := strings.Split(string(out), "PARTUUID=")
-	if len(parts) != 2 {
-		ctx.Warn("failed to parse the partuuid of %s\n", part)
-		return ""
+	if pType, ok := info["ID_PART_ENTRY_UUID"]; ok {
+		return pType
 	}
-
-	return strings.ReplaceAll(strings.TrimSpace(parts[1]), `"`, "")
+	return util.UNKNOWN
 }
 
 func diskIsRemovable(paths *linuxpath.Paths, disk string) bool {

pkg/block/block_linux_test.go

@@ -288,6 +288,37 @@ func TestDiskTypeUdev(t *testing.T) {
 	}
 }
 
+func TestDiskPartUUID(t *testing.T) {
+	if _, ok := os.LookupEnv("GHW_TESTING_SKIP_BLOCK"); ok {
+		t.Skip("Skipping block tests.")
+	}
+	baseDir, _ := ioutil.TempDir("", "test")
+	defer os.RemoveAll(baseDir)
+	ctx := context.New()
+	ctx.Chroot = baseDir
+	paths := linuxpath.New(ctx)
+	partUUID := "11111111-1111-1111-1111-111111111111"
+
+	_ = os.MkdirAll(paths.SysBlock, 0755)
+	_ = os.MkdirAll(paths.RunUdevData, 0755)
+
+	// Emulate a disk with one partition with uuid
+	_ = os.Mkdir(filepath.Join(paths.SysBlock, "sda"), 0755)
+	_ = os.Mkdir(filepath.Join(paths.SysBlock, "sda", "sda1"), 0755)
+	_ = ioutil.WriteFile(filepath.Join(paths.SysBlock, "sda", "sda1", "dev"), []byte("259:0\n"), 0644)
+	_ = ioutil.WriteFile(filepath.Join(paths.RunUdevData, "b259:0"), []byte(fmt.Sprintf("E:ID_PART_ENTRY_UUID=%s\n", partUUID)), 0644)
+	uuid := diskPartUUID(paths, "sda", "sda1")
+	if uuid != partUUID {
+		t.Fatalf("Got uuid %s but expected %s", uuid, partUUID)
+	}
+
+	// Check empty uuid if not found
+	uuid = diskPartUUID(paths, "sda", "sda2")
+	if uuid != util.UNKNOWN {
+		t.Fatalf("Got uuid %s, but expected %s label", uuid, util.UNKNOWN)
+	}
+}
+
 // TestLoopDevicesWithOption tests to see if we find loop devices when the option is activated
 func TestLoopDevicesWithOption(t *testing.T) {
 	if _, ok := os.LookupEnv("GHW_TESTING_SKIP_BLOCK"); ok {