diff --git a/MD/centos.sh b/MD/centos.sh
index d3d1c88..5d0e898 100644
--- a/MD/centos.sh
+++ b/MD/centos.sh
@@ -1,76 +1,93 @@
 #!/usr/bin/bash
-list(){
-echo "--------------------------------------"
-echo "------------性能优化工具箱------------"
-echo "------------1.更换YUM源---------------"
-echo "------------2.关闭防火墙--------------"
-echo "------------3.时间同步----------------"
-echo "------------4.创建用户----------------"
-echo "------------5.安装软件----------------"
-echo "------------6.EXIT--------------------"
+
+# 输出菜单
+list() {
+    echo "--------------------------------------"
+    echo "------------性能优化工具箱------------"
+    echo "--------------------------------------"
+    echo "1. 更换 YUM 源"
+    echo "2. 关闭防火墙"
+    echo "3. 时间同步"
+    echo "4. 创建用户"
+    echo "5. 安装常用软件"
+    echo "6. 退出"
+    echo "--------------------------------------"
 }
-yuan(){
-	rm -rf /etc/yum.repos.d/*
-	curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo &>/dev/null
-	curl -o /etc/yum.repos.d/epel.repo https://mirrors.aliyun.com/repo/epel-7.repo &>/dev/null
-	yum clean all
-	yum makecache fast
+
+# 更换 YUM 源
+yuan() {
+    echo "正在更换 YUM 源..."
+    rm -rf /etc/yum.repos.d/*
+    if curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo &>/dev/null && \
+       curl -o /etc/yum.repos.d/epel.repo https://mirrors.aliyun.com/repo/epel-7.repo &>/dev/null; then
+        yum clean all
+        yum makecache fast
+        echo "YUM 源更换完成！"
+    else
+        echo "YUM 源更换失败，请检查网络或链接。"
+    fi
 }
-fire(){
-	systemctl stop firewalld
-	systemctl disable firewalld
-	setenforce 0 #临时关闭
-	sed -ri s/SELINUX=enforcing/SELINUX=disabled/g /etc/selinux/config  #永久关闭
+
+# 关闭防火墙
+fire() {
+    echo "正在关闭防火墙..."
+    systemctl stop firewalld
+    systemctl disable firewalld
+    setenforce 0 # 临时关闭 SELinux
+    sed -ri 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/selinux/config  # 永久关闭 SELinux
+    echo "防火墙已关闭，SELinux 已禁用（需重启生效）。"
 }
-timed(){
-	yum -y install ntpdate &>/dev/null
-	ntpdate aliyun.com
+
+# 时间同步
+timed() {
+    echo "正在安装和同步时间..."
+    if yum -y install ntpdate &>/dev/null; then
+        ntpdate ntp1.aliyun.com
+        echo "时间同步成功！"
+    else
+        echo "时间同步失败，请检查网络连接或 YUM 配置。"
+    fi
 }
-user(){
-	read -p "请输入你要创建的用户名字:" name
-	useradd $name
-	userpasswd=`echo $RANDOM`
-	echo $userpasswd|passwd --stdin $name &>/dev/null
-	if [ $? -eq 0 ];then
-		echo "用户名：$name的密码：$userpasswd">>/opt/user.txt
-		echo "用户创建成功"
-	else
-		exit
-		fi
+
+# 创建用户
+user() {
+    read -p "请输入要创建的用户名：" name
+    if id "$name" &>/dev/null; then
+        echo "用户 $name 已存在，请勿重复创建。"
+    else
+        useradd "$name"
+        userpasswd=$(openssl rand -base64 8)
+        echo "$userpasswd" | passwd --stdin "$name" &>/dev/null
+        if [ $? -eq 0 ]; then
+            echo "用户名：$name，密码：$userpasswd" >> /opt/user.txt
+            echo "用户 $name 创建成功，密码已存储在 /opt/user.txt 中。"
+        else
+            echo "用户创建失败，请检查系统配置。"
+        fi
+    fi
 }
-anzhuang(){
-	yum -y install vim lsof unzip wget &>/dev/null
+
+# 安装常用软件
+anzhuang() {
+    echo "正在安装常用软件（vim、lsof、unzip、wget）..."
+    if yum -y install vim lsof unzip wget &>/dev/null; then
+        echo "常用软件安装完成！"
+    else
+        echo "软件安装失败，请检查 YUM 源配置。"
+    fi
 }
-while :
-do
-list
-read -p "请输入您的选项：" num
-case $num in
-1)
-	yuan
-	sleep 3
-;;
-2)
-	fire
-	sleep 3
-;;
-3)
-	timed
-	sleep 3
-;;
-4)
-	user
-	sleep 3
-;;
-5)
-	anzhuang
-	sleep 3
-;;
-6)
-	exit
-;;
-*)
-	echo "请您按要求输入:(12345)"
-;;
-esac
+
+# 主循环
+while true; do
+    list
+    read -p "请输入您的选项（1-6）：" num
+    case $num in
+    1) yuan; sleep 2 ;;
+    2) fire; sleep 2 ;;
+    3) timed; sleep 2 ;;
+    4) user; sleep 2 ;;
+    5) anzhuang; sleep 2 ;;
+    6) echo "退出工具箱，感谢使用！"; exit ;;
+    *) echo "输入无效，请输入数字 1-6 选择功能。"; sleep 2 ;;
+    esac
 done