Auto Scaling:Automatically mount an NAS file system to an ECS instance

Create the policy

1. Log on to the RAM console.

2. In the left-side navigation pane, choose Permissions > Policies.

3. Click Create Policy.

4. On the Create Policy page, click the JSON tab and enter the following policy document:

   {
       "Version": "1",
       "Statement": [
           {
               "Action": [
                   "ecs:DescribeInvocations",
                   "ecs:RunCommand",
                   "ecs:DescribeInvocationResults",
                   "ecs:DescribeInstances"
               ],
               "Resource": "*",
               "Effect": "Allow"
           },
           {
               "Action": [
                   "ess:CompleteLifecycleAction"
               ],
               "Resource": "*",
               "Effect": "Allow"
           }
       ]
   }

5. Set Name to ESSHookPolicyForAttachNAS, then click OK.

Attach the policy to the RAM role

1. In the left-side navigation pane, choose Identities > Roles.

2. Find OOSServiceRole and click Grant Permission in the Actions column.

3. In the Grant Permission panel, configure the following settings and click Grant permissions:

   Parameter	Value
   Resource Scope	Account
   Policies	ESSHookPolicyForAttachNAS (custom policy)

Create the lifecycle hook

1. Log on to the Auto Scaling console.

2. In the left-side navigation pane, click Scaling Groups.

3. In the top navigation bar, select your region.

4. Find your scaling group and click its ID or click Details in the Actions column.

5. On the details page, click the Lifecycle Hook tab, then click Create Lifecycle Hook.

6. Configure the following parameters and click OK: For Send Notification When Lifecycle Hook Takes Effect, configure the OOS template parameters:

   Set Timeout Period long enough for the mount operation to complete. If the timeout expires before the operation finishes, the lifecycle hook action fails. Estimate the time needed and add a buffer.

   Parameter	Value
   Name	ESSHookForAttachNAS
   Scaling Activity	Scale-out Event
   Timeout Period	300 (seconds)
   Default Execution Policy	Continue
   Send Notification When Lifecycle Hook Takes Effect	OOS Template > Public Templates > ACS-ESS-LifeCycleAttachNASFileSystemToInstance

   Parameter	Description	Example
   mountTargetDomain	Domain name of the NAS mount target	<your-mount-target-domain>
   MountDir	Directory on the ECS instance where the NAS file system is mounted	/mnt (default)
   FileSystemVersion	NFS protocol version: 0 for NFSv4, 1 for NFSv3	0
   RateControl	Execution rate: Batch-based Control or Concurrency-based Control	Concurrency-based Control
   OOSAssumeRole	The RAM role OOS assumes to run the template	OOSServiceRole

Trigger a scale-out event

Lifecycle hooks take effect only when scaling activities are triggered by executing scaling rules — not when you manually add or remove instances.

This example uses a simple scaling rule to trigger a scale-out.

1. On the scaling group details page, click the Scaling Rules and Event-triggered Tasks tab.

2. On the Scaling Rules tab, click Create Scaling Rule.

3. Configure the following settings and click OK:

   Parameter	Value
   Rule Name	Add1
   Rule Type	Simple Scaling Rule
   Operation	Add 1 Instances

4. Find the Add1 scaling rule and click Execute in the Actions column.

5. In the Execute Scaling Rule message, click OK.

Auto Scaling adds one ECS instance to the scaling group. The instance enters the Pending Add state while the ESSHookForAttachNAS lifecycle hook is active. During this window, Auto Scaling notifies OOS to run the ACS-ESS-LifeCycleAttachNASFileSystemToInstance template and mount the NAS file system.