diff --git a/internal/manifest/manifest.go b/internal/manifest/manifest.go
index 89ca4b9b..893c96f4 100644
--- a/internal/manifest/manifest.go
+++ b/internal/manifest/manifest.go
@@ -334,6 +334,7 @@ func fastValidate(options *WriteOptions) (err error) {
 		}
 		sliceExist[slice.String()] = true
 	}
+	hardLinkGroups := make(map[uint64][]*ReportEntry)
 	for _, entry := range options.Report.Entries {
 		err := validateReportEntry(&entry)
 		if err != nil {
@@ -344,7 +345,38 @@ func fastValidate(options *WriteOptions) (err error) {
 				return fmt.Errorf("path %q refers to missing slice %s", entry.Path, slice.String())
 			}
 		}
+		if entry.HardLinkId != NON_HARD_LINK {
+			e := entry
+			hardLinkGroups[e.HardLinkId] = append(hardLinkGroups[e.HardLinkId], &e)
+		}
+	}
+	// Entries within a hard link group must have same content.
+	var linkIDs []uint64
+	for id := range hardLinkGroups {
+		linkIDs = append(linkIDs, id)
+	}
+	sort.Slice(linkIDs, func(i, j int) bool {
+		return linkIDs[i] < linkIDs[j]
+	})
+	for i, id := range linkIDs {
+		if uint64(i+1) != id {
+			return fmt.Errorf("skipped hard link ID %d, but %d exists", i+1, id)
+		}
+		entries := hardLinkGroups[id]
+		if len(entries) == 1 {
+			return fmt.Errorf("hard link group %d has only one path: %s", id, entries[0].Path)
+		}
+		sort.Slice(entries, func(i, j int) bool {
+			return entries[i].Path < entries[j].Path
+		})
+		e0 := entries[0]
+		for _, e := range entries[1:] {
+			if e.Link != e0.Link || e.Mode != e0.Mode || e.SHA256 != e0.SHA256 || e.Size != e0.Size {
+				return fmt.Errorf("hard linked paths %q and %q have diverging contents", e0.Path, e.Path)
+			}
+		}
 	}
+
 	return nil
 }
 
diff --git a/internal/manifest/manifest_test.go b/internal/manifest/manifest_test.go
index 1259d819..521f3449 100644
--- a/internal/manifest/manifest_test.go
+++ b/internal/manifest/manifest_test.go
@@ -295,6 +295,16 @@ var generateManifestTests = []struct {
 				Size:        1234,
 				Slices:      map[*setup.Slice]bool{slice1: true},
 				FinalSHA256: "final-hash",
+				HardLinkId:  1,
+			},
+			"/hardlink": {
+				Path:        "/hardlink",
+				Mode:        0456,
+				SHA256:      "hash",
+				Size:        1234,
+				Slices:      map[*setup.Slice]bool{slice1: true},
+				FinalSHA256: "final-hash",
+				HardLinkId:  1,
 			},
 			"/link": {
 				Path:   "/link",
@@ -324,6 +334,16 @@ var generateManifestTests = []struct {
 			Size:        1234,
 			SHA256:      "hash",
 			FinalSHA256: "final-hash",
+			HardLinkId:  1,
+		}, {
+			Kind:        "path",
+			Path:        "/hardlink",
+			Mode:        "0456",
+			Slices:      []string{"package1_slice1"},
+			Size:        1234,
+			SHA256:      "hash",
+			FinalSHA256: "final-hash",
+			HardLinkId:  1,
 		}, {
 			Kind:   "path",
 			Path:   "/link",
@@ -355,6 +375,10 @@ var generateManifestTests = []struct {
 			Kind:  "content",
 			Slice: "package1_slice1",
 			Path:  "/file",
+		}, {
+			Kind:  "content",
+			Slice: "package1_slice1",
+			Path:  "/hardlink",
 		}, {
 			Kind:  "content",
 			Slice: "package1_slice1",
@@ -539,6 +563,56 @@ var generateManifestTests = []struct {
 		},
 	},
 	error: `internal error: invalid manifest: path "/dir" has invalid options: size set for directory`,
+}, {
+	summary: "Invalid path: skipped hard link ID",
+	report: &manifest.Report{
+		Root: "/",
+		Entries: map[string]manifest.ReportEntry{
+			"/file": {
+				Path:       "/file",
+				Slices:     map[*setup.Slice]bool{slice1: true},
+				HardLinkId: 2,
+			},
+		},
+	},
+	error: `internal error: invalid manifest: skipped hard link ID 1, but 2 exists`,
+}, {
+	summary: "Invalid path: hard link group has only one path",
+	report: &manifest.Report{
+		Root: "/",
+		Entries: map[string]manifest.ReportEntry{
+			"/file": {
+				Path:       "/file",
+				Slices:     map[*setup.Slice]bool{slice1: true},
+				HardLinkId: 1,
+			},
+		},
+	},
+	error: `internal error: invalid manifest: hard link group 1 has only one path: /file`,
+}, {
+	summary: "Invalid path: hard linked paths differ",
+	report: &manifest.Report{
+		Root: "/",
+		Entries: map[string]manifest.ReportEntry{
+			"/file": {
+				Path:       "/file",
+				Mode:       0456,
+				SHA256:     "hash",
+				Size:       1234,
+				Slices:     map[*setup.Slice]bool{slice1: true},
+				HardLinkId: 1,
+			},
+			"/hardlink": {
+				Path:       "/hardlink",
+				Mode:       0456,
+				SHA256:     "different-hash",
+				Size:       1234,
+				Slices:     map[*setup.Slice]bool{slice1: true},
+				HardLinkId: 1,
+			},
+		},
+	},
+	error: `internal error: invalid manifest: hard linked paths "/file" and "/hardlink" have diverging contents`,
 }, {
 	summary: "Invalid package: missing name",
 	packageInfo: []*archive.PackageInfo{{