diff --git a/README.md b/README.md
index 40fe491..bc9727f 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ This repository contains resources and configuration scripts for building a cust
 
 ## Supported OS
 
-* CentOS 7.6/7.7
+* CentOS 7.6/7.7/7.8/7.9
 * Aliyun Linux 2 (Alibaba Cloud Linux 2)
 
 ## Setup
@@ -15,16 +15,6 @@ You must have [Packer](https://www.packer.io/) installed on your local system. F
 
 For more information, see [Alibaba Cloud builder](https://www.packer.io/docs/builders/alicloud-ecs.html) in the Packer documentation.
 
-## Building the OS Image
-
-Execute following scripts in your shell
-
-```
-export ALICLOUD_ACCESS_KEY=XXX
-export ALICLOUD_SECRET_KEY=XXX
-packer build examples/ack-centos.json
-```
-
 ## Build ACK-Optimized-OS image
 
 Execute following scripts in your shell
@@ -35,6 +25,16 @@ export ALICLOUD_SECRET_KEY=XXX
 packer build examples/ack-optimized-os.json
 ```
 
+## Building the OS Image
+
+Execute following scripts in your shell
+
+```
+export ALICLOUD_ACCESS_KEY=XXX
+export ALICLOUD_SECRET_KEY=XXX
+packer build examples/ack-centos.json
+```
+
 ## Building in the kubernetes
 
 ```shell script
diff --git a/examples/ack-aliyunlinux2.json b/examples/ack-aliyunlinux2.json
index 51002e2..0ac1fd0 100644
--- a/examples/ack-aliyunlinux2.json
+++ b/examples/ack-aliyunlinux2.json
@@ -2,7 +2,7 @@
   "variables": {
     "region": "cn-hangzhou",
     "image_name": "test_image{{timestamp}}",
-    "source_image": "aliyun_2_1903_x64_20G_alibase_20200904.vhd",
+    "source_image": "aliyun_2_1903_x64_20G_alibase_20210120.vhd",
     "instance_type": "ecs.g6.large",
     "access_key": "{{env `ALICLOUD_ACCESS_KEY`}}",
     "secret_key": "{{env `ALICLOUD_SECRET_KEY`}}"
diff --git a/examples/ack-centos-using-existing-vpc-vswitch.json b/examples/ack-centos-using-existing-vpc-vswitch.json
index b70bcb3..dcd3ed9 100644
--- a/examples/ack-centos-using-existing-vpc-vswitch.json
+++ b/examples/ack-centos-using-existing-vpc-vswitch.json
@@ -2,7 +2,7 @@
   "variables": {
     "region": "cn-hangzhou",
     "image_name": "test_image{{timestamp}}",
-    "source_image": "centos_7_7_x64_20G_alibase_20200426.vhd",
+    "source_image": "centos_7_9_x64_20G_alibase_20210128.vhd",
     "instance_type": "ecs.g6.large",
     "vpc_id": "vpc-xxxxxx",
     "vswitch_id": "vsw-xxxxxx",
diff --git a/examples/ack-centos.json b/examples/ack-centos.json
index b3bb714..5a79efc 100644
--- a/examples/ack-centos.json
+++ b/examples/ack-centos.json
@@ -2,7 +2,7 @@
   "variables": {
     "region": "cn-hangzhou",
     "image_name": "test_image{{timestamp}}",
-    "source_image": "centos_7_7_x64_20G_alibase_20200426.vhd",
+    "source_image": "centos_7_9_x64_20G_alibase_20210128.vhd",
     "instance_type": "ecs.g6.large",
     "access_key": "{{env `ALICLOUD_ACCESS_KEY`}}",
     "secret_key": "{{env `ALICLOUD_SECRET_KEY`}}"
diff --git a/examples/ack-kubernetes.json b/examples/ack-kubernetes.json
index 8db552b..a0f2257 100644
--- a/examples/ack-kubernetes.json
+++ b/examples/ack-kubernetes.json
@@ -2,7 +2,7 @@
   "variables": {
     "region": "{{env `REGION`}}",
     "image_name": "test_image{{timestamp}}",
-    "source_image": "centos_7_7_x64_20G_alibase_20200426.vhd",
+    "source_image": "centos_7_9_x64_20G_alibase_20210128.vhd",
     "instance_type": "ecs.g6.large",
     "access_key": "{{env `ALICLOUD_ACCESS_KEY`}}",
     "secret_key": "{{env `ALICLOUD_SECRET_KEY`}}",
@@ -42,4 +42,4 @@
       ]
     }
   ]
-}
\ No newline at end of file
+}
diff --git a/examples/ack-optimized-os.json b/examples/ack-optimized-os.json
index 11cad5c..ae72ff1 100644
--- a/examples/ack-optimized-os.json
+++ b/examples/ack-optimized-os.json
@@ -2,7 +2,7 @@
   "variables": {
     "region": "cn-hangzhou",
     "image_name": "ack-optimized_image{{timestamp}}",
-    "source_image": "aliyun_2_1903_x64_20G_alibase_20200904.vhd",
+    "source_image": "aliyun_2_1903_x64_20G_alibase_20210120.vhd",
     "instance_type": "ecs.g6.large",
     "access_key": "{{env `ALICLOUD_ACCESS_KEY`}}",
     "secret_key": "{{env `ALICLOUD_SECRET_KEY`}}"