Instance template

When creating a group, you need to describe an instance template, which is the basic instance configuration used for deploying all instances in the group.

Both the template and policy description are provided to the CLI in a YAML file using the --file flag when creating or updating an instance group. This is a convenient method to provide values that consist of multiple strings. For more information, see Create a fixed-size instance group.

You can set variable values for the instance template. For more information, see Variables in an instance template.

Computing resourcesComputing resources

When describing a template, you specify the computing resources to allocate to each instance, i.e., the number and guaranteed performance of processor cores (vCPUs) and the amount of RAM. You can choose the computing resources that are appropriate for the expected load. For more information, see vCPU performance levels.

You can also use a template to enable creating preemptible instances, which are cheaper than regular ones. Preemptible instances can only be autohealed if the computing resources in the availability zone allow for this. If the resources are insufficient, Instance Groups will resume autohealing as soon as the resources become available; this, however, may take a long time.

DisksDisks

Each instance must have at least one disk attached, which is a boot disk. Each boot disk is created automatically and attached to a single instance when creating an instance group. For more information, see Disks.

You can also attach additional disks to each instance. You can create an additional disk along with an instance group. You can create an empty disk or restore it from a snapshot or an image. You can only attach or detach additional disks when creating or updating a group. You can update secondary disks by updating YAML specification.

NetworkNetwork

When creating a group, you can:

• Set the network for the entire group.
• Set subnets for each instance in the group.

You can create a group without specifying any subnets for its instances if the availability zone selected for each instance contains exactly one subnet for the specified network.

You can also configure a public IP address for each instance. This allows the instance to connect to other services over the internet. For more information, see VM networking.

You can specify the appropriate security groups in a template or configure them individually for each instance in the group.

MetadataMetadata

You can use a template to describe the metadata for the instances in the group. For example, you can use the user-data key to describe the system users to be created on new instance startup. For more information about the metadata supported by Compute Cloud, see VM metadata.

Template description in a YAML fileTemplate description in a YAML file

A template describes the configuration of the base instance. It is defined in the instance_template key in a YAML file.

Here is how a YAML file entry may look like:

...
instance_template:
  platform_id: standard-v3
  resources_spec:
    memory: 2G
    cores: 2
    core_fraction: 20
  boot_disk_spec:
    mode: READ_WRITE
    disk_spec:
      image_id: jk9ib7ecsbrj********
      type_id: network-hdd
      size: 50G
  secondary_disk_specs:
    - name: disk-2
      mode: READ_WRITE
      disk_spec:
        preserve_after_instance_delete: false
        type_id: network-hdd
        size: 21474836480
  network_interface_specs:
    - network_id: adv1rq7pmi05********
      subnet_ids:
        - u8zxv2v5f3rr********
      primary_v4_address_spec: {
        one_to_one_nat_spec: {
          ip_version: IPV4
        }
      }
  placement_policy:
    placement_group_id: rmppvhrgm77g********
  metadata:
    user-data: |-
      #cloud-config
      write_files:
        - path: /var/lib/cloud/scripts/per-boot/01-run-load-generator.sh
          permissions: '0555'
          content: |
            #!/bin/bash
            docker run -d --net=host -p 80:80 openresty/openresty:alpine
      users:
        - name: my-user
          groups: sudo
          shell: /bin/bash
          sudo: 'ALL=(ALL) NOPASSWD:ALL'
          ssh-authorized-keys:
            - ssh-ed25519 AAAAB3...
...

By default, the disk size is specified in bytes. You can specify a different unit of measurement using the applicable suffix.

Keys (the table lists keys that directly define the base instance configuration):

For information about the technical restrictions of Instance Groups, see Quotas and limits in Compute Cloud.