When you create a CentOS system, you must manually configure a YUM repository to install common software on the system. A YUM repository is a collection of software packages. Different versions of CentOS require different YUM repositories. Resource Orchestration Service (ROS) allows you to automate the configuration of YUM repositories for different versions of CentOS by creating stacks based on templates that define mappings.

Step 1: Edit a template

Mappings are defined in the following template. The mappings contain the URLs of YUM repositories for multiple versions of CentOS. When you create an Elastic Compute Service (ECS) instance and initialize the system for the instance, the Fn::FindInMap function returns the URL of the YUM repository that matches the version of the image specified by InstanceImageId. 

ROSTemplateFormatVersion: '2015-09-01'
Description: Creates ECS Centos system instance, and set yum repo.
Metadata:
  ALIYUN::ROS::Interface:
    ParameterGroups:
      - Parameters:
          - VSwitchZoneId
          - InstanceImageId
          - InstanceType
          - SystemDiskSize
          - InstancePublicIP
          - InstancePassword
          - SystemDiskCategory
        Label:
          default: ECS
    TemplateTags:
      - Creates VPC ECS instance
Parameters:
  SystemDiskCategory:
    Type: String
    Label:
      en: System Disk Type
    Description:
      en: '<font color=''blue''><b>Optional values:</b></font><br>[cloud_efficiency: <font color=''green''>Efficient Cloud Disk</font>]<br>[cloud_ssd: <font color=''green''>SSD Cloud Disk</font>]<br>[cloud_essd: <font color=''green''>ESSD Cloud Disk</font>]<br>[cloud: <font color=''green''>Cloud Disk</font>]<br>[ephemeral_ssd: <font color=''green''>Local SSD Cloud Disk</font>]'
    AllowedValues:
      - cloud_efficiency
      - cloud_ssd
      - cloud
      - cloud_essd
      - ephemeral_ssd
    Default: cloud_ssd
  InstanceImageId:
    Type: String
    Default: centos_7
    AllowedValues:
      - centos_6
      - centos_7
      - centos_8
    Description:
      en: Image ID,support [centos_6,centos_7,centos_8]
    Label:
      en: Image
  InstanceType:
    Type: String
    Description:
      en: 'Fill in the specifications that can be used under the VSwitch availability zone;</b></font><br>general specifications: <font color=''red''><b>ecs.c5.large</b></font><br>note: a few zones do not support general specifications<br>see detail: <a href=''https://www.alibabacloud.com/help/en/doc-detail/25378.html'' target=''_blank''><b><font color=''blue''>Instance Specification Family</font></a></b>'
    Label:
      en: Instance Type
    AssociationProperty: ALIYUN::ECS::Instance::InstanceType
    AssociationPropertyMetadata:
      ZoneId: VSwitchZoneId
  InstancePassword:
    NoEcho: true
    Type: String
    Description:
      en: Server login password, Length 8-30, must contain three(Capital letters, lowercase letters, numbers, ()`~!@#$%^&*_-+=|{}[]:;'<>,.?/ Special symbol in).
    AllowedPattern: '[0-9A-Za-z\_\-\&:;''<>,=%`~!@#\(\)\$\^\*\+\|\{\}\[\]\.\?\/]+$'
    Label:
      en: Instance Password
    ConstraintDescription:
      en: Length 8-30, must contain three(Capital letters, lowercase letters, numbers, ()`~!@#$%^&*_-+=|{}[]:;'<>,.?/ Special symbol in).
    MinLength: 8
    MaxLength: 30
  InstancePublicIP:
    Type: Boolean
    Description:
      en: Whether to assign a common IP.
    Label:
      en: Allocate Public IP
    Default: false
  VSwitchZoneId:
    AssociationProperty: ALIYUN::ECS::Instance:ZoneId
    Type: String
    Description:
      en: Availability Zone ID.<br><b>note: <font color='blue'>before selecting, please confirm that the Availability Zone supports the specification of creating ECS resources,which is recommended to be different from other VSwitch Availability Zone</font></b>
    Label:
      en: VSwitch Availability Zone
  SystemDiskSize:
    Default: 40
    Type: Number
    Description:
      en: 'System disk size, range of values: 40-500, units: GB.'
    Label:
      en: System Disk Space
Mappings:
  YumMap:
    centos_6:
      YumSource: http://mirrors.aliyun.com/repo/Centos-6.repo
    centos_7:
      YumSource: http://mirrors.aliyun.com/repo/Centos-7.repo
    centos_8:
      YumSource: http://mirrors.aliyun.com/repo/Centos-8.repo
Resources:
  RosConditionHandle:
    Type: ALIYUN::ROS::WaitConditionHandle
  RosWaitCondition:
    Type: ALIYUN::ROS::WaitCondition
    DependsOn: EcsInstance
    Properties:
      Timeout: 1800
      Count: 1
      Handle:
        Ref: RosConditionHandle
  EcsVSwitch:
    Type: ALIYUN::ECS::VSwitch
    Properties:
      VpcId:
        Ref: EcsVpc
      ZoneId:
        Ref: VSwitchZoneId
      CidrBlock: 192.168.0.0/24
  EcsInstance:
    Type: ALIYUN::ECS::Instance
    Properties:
      UserData:
        Fn::Sub:
          - |
            #!/bin/bash
            mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
            curl -o /etc/yum.repos.d/CentOS-Base.repo ${yum_repo}
            yum clean all
            yum makecache
            ${ros-notify} -d '{"data" : "Install Centos success."}'
          - ros-notify:
              Fn::GetAtt:
                - RosConditionHandle
                - CurlCli
            yum_repo:
              Fn::FindInMap:
                - YumMap
                - Ref: InstanceImageId
                - YumSource
      IoOptimized: optimized
      PrivateIpAddress: 192.168.0.1
      VpcId:
        Ref: EcsVpc
      SecurityGroupId:
        Ref: EcsSecurityGroup
      VSwitchId:
        Ref: EcsVSwitch
      ImageId:
        Ref: InstanceImageId
      AllocatePublicIP:
        Ref: InstancePublicIP
      InstanceType:
        Ref: InstanceType
      SystemDiskSize:
        Ref: SystemDiskSize
      SystemDiskCategory:
        Ref: SystemDiskCategory
      Password:
        Ref: InstancePassword
  EcsSecurityGroup:
    Type: ALIYUN::ECS::SecurityGroup
    Properties:
      VpcId:
        Ref: EcsVpc
      SecurityGroupIngress:
        - PortRange: '-1/-1'
          Priority: 1
          SourceCidrIp: 0.0.0.0/0
          IpProtocol: all
          NicType: intranet
      SecurityGroupEgress:
        - PortRange: '-1/-1'
          Priority: 1
          IpProtocol: all
          DestCidrIp: 0.0.0.0/0
          NicType: intranet
  EcsVpc:
    Type: ALIYUN::ECS::VPC
    Properties:
      CidrBlock: 192.168.0.0/16
      VpcName:
        Fn::Join:
          - '-'
          - - StackId
            - Ref: ALIYUN::StackId
Outputs:
  EcsInstanceId:
    Value:
      Fn::GetAtt:
        - EcsInstance
        - InstanceId

Step 2: Create a stack

  1. Log on to the ROS console.
  2. In the left-side navigation pane, click Stacks.
  3. In the upper-left corner of the page, select the region in which you want to create a stack from the drop-down list.
  4. On the Stacks page, click Create Stack and select Use New Resources (Standard) from the drop-down list.
  5. In the Select Template step, select Select an Existing Template. Set Template Import Method to Enter Template Content, enter the YAML template content you edited in Step 1 into the Template Content code editor, and then click Next.
  6. In the Configure Template Parameters step, set Stack Name and the following parameters.
    ParameterDescriptionExample
    VSwitch Availability ZoneThe zone ID of the resource. Qingdao Zone C
    ImageThe image ID of the ECS instance.

    Default value: centos_7.

    For more information, see Image overview.

    		centos_7
    Instance TypeThe instance type of the ECS instance.

    Select a valid instance type. For more information, see Overview of instance families.

    		ecs.c5.large
    System Disk SpaceThe system disk size of the ECS instance.

    Valid values: 40 to 500.

    Unit: GB

    		40
    Allocate Public IPSpecifies whether to allocate a public IP address to the ECS instance.
    • If you turn on Allocate Public IP, the system allocates a public IP address.
    • If you turn off Allocate Public IP, the system does not allocate a public IP address.
    		Turn on Allocate Public IP
    Instance PasswordThe password that is used to log on to the ECS instance. Test_12****
    System Disk TypeThe system disk category of the ECS instance. Valid values:
    • cloud_efficiency: ultra disk
    • cloud_ssd: standard SSD
    • cloud_essd: enhanced SSD (ESSD)
    • cloud: basic disk
    • ephemeral_ssd: local SSD

    For more information, see Disks.

    		cloud_efficiency
  7. Click Create.
  8. View the stack status on the Stack Information tab of the stack management page. After the stack is created, click the Outputs tab to obtain the ID of the ECS instance.
  9. Connect to the ECS instance in the ECS console to view the YUM repository.
    For more information about how to connect to an ECS instance, see Overview.

Step 3: View resources

  1. Log on to the ROS console.
  2. In the left-side navigation pane, click Stacks.
  3. On the Stacks page, click the ID of the stack that you created.
  4. On the stack management page, click the Resources tab to view resources.
    The following table describes the resources in this example.
    ResourceQuantityDescriptionSpecifications
    ALIYUN::ECS::Instance1Creates an ECS instance.
    • A single instance of the following specifications is created:
    • InstanceType: ecs.c5.large
    • SystemDiskCategory: cloud_efficiency
    • SystemDiskSize: 40 (Unit: GB)
    • AllocatePublicIP: true
    Note For more information about the resource charges, see the pricing schedule on the official website or the product pricing documentation.