diff --git a/cmd/fuserdb/main.go b/cmd/fuserdb/main.go
index 9283d82..6f10ee7 100644
--- a/cmd/fuserdb/main.go
+++ b/cmd/fuserdb/main.go
@@ -2,7 +2,6 @@ package main
 
 import (
 	"bytes"
-	"encoding/json"
 	"errors"
 	"flag"
 	"fmt"
@@ -46,18 +45,9 @@ func main() {
 		fmsg.Fatalf("cannot create output: %v", err)
 	}
 
-	type payload struct {
-		UserName      string `json:"userName"`
-		Uid           int    `json:"uid"`
-		Gid           int    `json:"gid"`
-		RealName      string `json:"realName"`
-		HomeDirectory string `json:"homeDirectory"`
-		Shell         string `json:"shell"`
-	}
-
 	for _, u := range users {
 		fidString := strconv.Itoa(u.fid)
-		for aid := 0; aid < 9999; aid++ {
+		for aid := 0; aid < 10000; aid++ {
 			userName := fmt.Sprintf("u%d_a%d", u.fid, aid)
 			uid := 1000000 + u.fid*10000 + aid
 			us := strconv.Itoa(uid)
@@ -69,27 +59,11 @@ func main() {
 				homeDirectory = varEmpty
 			}
 
-			fileName := userName + ".user"
-			if f, err := os.OpenFile(path.Join(*out, fileName), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644); err != nil {
-				fmsg.Fatalf("cannot create %s: %v", userName, err)
-			} else if err = json.NewEncoder(f).Encode(&payload{
-				UserName:      userName,
-				Uid:           uid,
-				Gid:           uid,
-				RealName:      realName,
-				HomeDirectory: homeDirectory,
-				Shell:         *shell,
-			}); err != nil {
-				fmsg.Fatalf("cannot serialise %s: %v", userName, err)
-			} else if err = f.Close(); err != nil {
-				fmsg.Printf("cannot close %s: %v", userName, err)
-			}
-			if err := os.Symlink(fileName, path.Join(*out, us+".user")); err != nil {
-				fmsg.Fatalf("cannot link %s: %v", userName, err)
-			}
+			writeUser(userName, uid, us, realName, homeDirectory, *shell, *out)
+			writeGroup(userName, uid, us, nil, *out)
 		}
 	}
 
-	fmsg.Printf("created %d entries", len(users)*10000)
+	fmsg.Printf("created %d entries", len(users)*2*10000)
 	fmsg.Exit(0)
 }
diff --git a/cmd/fuserdb/payload.go b/cmd/fuserdb/payload.go
new file mode 100644
index 0000000..fb24121
--- /dev/null
+++ b/cmd/fuserdb/payload.go
@@ -0,0 +1,64 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path"
+
+	"git.ophivana.moe/security/fortify/internal/fmsg"
+)
+
+type payloadU struct {
+	UserName      string   `json:"userName"`
+	Uid           int      `json:"uid"`
+	Gid           int      `json:"gid"`
+	MemberOf      []string `json:"memberOf,omitempty"`
+	RealName      string   `json:"realName"`
+	HomeDirectory string   `json:"homeDirectory"`
+	Shell         string   `json:"shell"`
+}
+
+func writeUser(userName string, uid int, us string, realName, homeDirectory, shell string, out string) {
+	userFileName := userName + ".user"
+	if f, err := os.OpenFile(path.Join(out, userFileName), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644); err != nil {
+		fmsg.Fatalf("cannot create %s: %v", userName, err)
+	} else if err = json.NewEncoder(f).Encode(&payloadU{
+		UserName:      userName,
+		Uid:           uid,
+		Gid:           uid,
+		RealName:      realName,
+		HomeDirectory: homeDirectory,
+		Shell:         shell,
+	}); err != nil {
+		fmsg.Fatalf("cannot serialise %s: %v", userName, err)
+	} else if err = f.Close(); err != nil {
+		fmsg.Printf("cannot close %s: %v", userName, err)
+	}
+	if err := os.Symlink(userFileName, path.Join(out, us+".user")); err != nil {
+		fmsg.Fatalf("cannot link %s: %v", userName, err)
+	}
+}
+
+type payloadG struct {
+	GroupName string   `json:"groupName"`
+	Gid       int      `json:"gid"`
+	Members   []string `json:"members,omitempty"`
+}
+
+func writeGroup(groupName string, gid int, gs string, members []string, out string) {
+	groupFileName := groupName + ".group"
+	if f, err := os.OpenFile(path.Join(out, groupFileName), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644); err != nil {
+		fmsg.Fatalf("cannot create %s: %v", groupName, err)
+	} else if err = json.NewEncoder(f).Encode(&payloadG{
+		GroupName: groupName,
+		Gid:       gid,
+		Members:   members,
+	}); err != nil {
+		fmsg.Fatalf("cannot serialise %s: %v", groupName, err)
+	} else if err = f.Close(); err != nil {
+		fmsg.Printf("cannot close %s: %v", groupName, err)
+	}
+	if err := os.Symlink(groupFileName, path.Join(out, gs+".group")); err != nil {
+		fmsg.Fatalf("cannot link %s: %v", groupName, err)
+	}
+}