Create a fixed-size instance group

You can create a group with a fixed number of instances. The group size is set manually. For more information, see Manually scaled groups.

Warning

When creating a group, keep the limits in mind. Not to disrupt the component Instance Groups, do not update or delete manually created resources: target group Load Balancer, virtual machines and disks. To do this, update or delete the instance group.

By default, all operations in Instance Groups are performed on behalf of a service account. If you don't have a service account, create one.

To create a fixed-size instance group:

Management console

CLI

API

To create a fixed-size instance group:

In the management console, select a folder to create your instance group in.
In the list of services, select Compute Cloud.
On the Virtual machines page, go to the Instance groups tab.
Click Create group.
Under Basic parameters:
- Enter a name and description of the instance group. Naming requirements:
  - The name must be unique within the folder.
  - The name may contain lowercase Latin letters, numbers, and hyphens.
  - The first character must be a letter. The last character can't be a hyphen.
  - The maximum length of the name is 63 characters.
  Note
  
  The VM name is used one time only when creating a VM, to generate the FQDN. If the FQDN is important to you, choose an appropriate name for the virtual machine at the creation stage. For more information about generating the FQDN, see Hostname and FQDN.
- Select a service account from the list or create a new one. To be able to create, update, and delete group instances, assign the editor role to the service account. All operations in Instance Groups are performed on behalf of the service account.
In the Allocation section, select the desired availability zones. Group instances may reside in different availability zones and regions. Learn more about Yandex.Cloud geography.
In the Instance template section, click Set to set the basic instance configuration:
- Select a public image.
- In the Disks section:
  - Select the disk type.
  - Specify the disk size.
    To add more disks, click Add disk.
- Under Computing resources:
  - Choose a platform.
  - Specify the guaranteed share and the necessary number of vCPUs and amount of RAM.
  - If necessary, make your VM preemptible.
    
    When creating a preemptible instance group, keep in mind that the virtual machines will terminate after 24 hours of continuous operation or earlier. It's possible that Instance Groups won't be able to restart them immediately due to insufficient resources. This may occur in the event of a drastic increase in Yandex.Cloud computing resource usage.
- Under Network settings:
  - Select the cloud network and the subnet. If the necessary subnet is not in the list, create it.
  - Specify if a public IP address is required.
  - Select the cloud network from the list, or specify its ID. If you don't have a network, click Create a new network to create one:
    - In the window that opens, enter a name for the new network and choose a subnet to connect the virtual machine to. Each network must have at least one subnet (if there's no subnet, create one). Then click Create.
  - In the Public IP field, choose a method for assigning an IP address:
    - Auto: Assign a random IP address from the Yandex.Cloud IP pool.
    - List: Select a public IP address from the list of previously reserved static addresses. For more information, see Making a dynamic public IP address static.
    - No address: Don't assign a public IP address.
  - If necessary, select DDoS protection.
- Under Access, specify the data required to access the VM:
  - Enter the username in the Login field.
  - Under SSH key, paste the contents of the public key file. You have to create a key pair for SSH connections on your own.
  - In the SSH key field, paste the contents of the public key file.
- Click Add.
Under Allow when creating and updating, specify:
- The number of instances that can exceed the group size.
- The number of instances the group size can be reduced by.
- The number of instances that can be created simultaneously.
- The number of instances that can be deleted simultaneously.
  
  For more information, see Deployment policy.
In the Scalability section:
- Select the scaling type. Currently, you can only create fixed-size groups.
- Specify the group size.
Click Create.
The instance group appears in the list.

If you don't have the Yandex.Cloud command line interface yet, install it.

The folder specified in the CLI profile is used by default. You can specify a different folder using the --folder-name or --folder-id parameter.

View a description of the create instance group command in the CLI:
```
$ yc compute instance-group create --help
```
Check whether there are networks in the folder:
```
$ yc vpc network list
```
If there aren't any, create one.

Select one of the public images (for example, CentOS 7).

To get a list of available images, run the following command:

$ yc compute image list --folder-id standard-images
+----------------------+-------------------------------------+--------------------------+----------------------+--------+
|          ID          |                NAME                 |          FAMILY          |     PRODUCT IDS      | STATUS |
+----------------------+-------------------------------------+--------------------------+----------------------+--------+
...
| fdvk34al8k5nltb58shr | centos-7-1549279494                 | centos-7                 | dqni65lfhvv2den5gtv9 | READY  |
| fdv7ooobjfl3ts9gqp0q | windows-2016-gvlk-1548913814        | windows-2016-gvlk        | dqnnc72gj2ist3ktjj1p | READY  |
| fdv4f5kv5cvf3ohu4flt | ubuntu-1604-lts-1549457823          | ubuntu-1604-lts          | dqnnb6dc7640c5i968ro | READY  |
...
+----------------------+-------------------------------------+--------------------------+----------------------+--------+

Create a YAML file with any name (for example, specification.yaml).

In the created file, indicate the following:

General information about the group:

name: first-fixed-group
service_account_id: <ID>
description: "This instance group was created from YAML config"

Keys:

Key	Value
`name`	A name for the instance group. The name must be unique within the folder. The name may contain lowercase Latin letters, numbers, and hyphens. The first character must be a letter. The last character can't be a hyphen. The maximum length of the name is 63 characters.
`service_account_id`	ID of the service account.
`description`	A description of the instance group.

Instance template, for example:

instance_template:
    platform_id: standard-v1
    resources_spec:
        memory: 4g
        cores: 1
    boot_disk_spec:
        mode: READ_WRITE
        disk_spec:
            image_id: fdvk34al8k5nltb58shr
            type_id: network-hdd
            size: 32g
    network_interface_specs:
        - network_id: c64mknqgnd8avp6edhbt
          primary_v4_address_spec: {}
    scheduling_policy:
        preemptible: false

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

Name	Example of a YAML file entry:
Kilobyte	1073741824k
Megabyte	1048576m
Gigabyte	1024g
Terabyte	1t

Keys (the table contains the keys that directly define the instance parameters):

Key	Value
`platform_id`	Platform ID.
`memory`	Amount of memory (RAM).
`cores`	Number of processor cores (vCPUs).
`mode`	Disk access mode. - `READ_ONLY`: read-only access. - `READ_WRITE`: read/write access.
`image_id`	CentOS 7 public image ID.
`type_id`	Disk type.
`size`	Disk size.
`network_id`	The `default-net` ID.
`primary_v4_address_spec`	IPv4 specification. Only IPv4 is currently available. You can allow public access to group instances by specifying the IP version for the public IP address. For more information, see Template description in a YAML file.
`scheduling_policy`	Scheduling policy configuration.
`preemptible`	A flag that enables the creation of preemptible instances. If the value is `true`, a preemptible instance is created, if `false` (default), a regular instance is created. When creating a preemptible instance group, keep in mind that the instances will terminate after 24 hours of continuous operation or earlier. It's possible that Instance Groups won't be able to restart them immediately due to insufficient resources. This may occur in the event of a drastic increase in Yandex.Cloud computing resource usage.

Policies:

deploy_policy:
    max_unavailable: 1
    max_expansion: 0
scale_policy:
    fixed_scale:
        size: 3
allocation_policy:
    zones:
        - zone_id: ru-central1-a

Keys:

Key	Value
`deploy_policy`	Deployment policy for instances in the group.
`scale_policy`	Scaling policy for instances in the group.
`allocation_policy`	Policy for allocating instances across zones and regions.

Full code for the specification.yaml file:

name: first-fixed-group
service_account_id: ajed6ilf11qg839dcl1e
description: "This instance group was created from YAML config"
instance_template:
    platform_id: standard-v1
    resources_spec:
        memory: 4g
        cores: 1
    boot_disk_spec:
        mode: READ_WRITE
        disk_spec:
            image_id: fdvk34al8k5nltb58shr
            type_id: network-hdd
            size: 32g
    network_interface_specs:
        - network_id: c64mknqgnd8avp6edhbt
          primary_v4_address_spec: {}
deploy_policy:
    max_unavailable: 1
    max_expansion: 0
scale_policy:
    fixed_scale:
        size: 3
allocation_policy:
    zones:
        - zone_id: ru-central1-a

Create an instance group in the default folder:
```
$ yc compute instance-group create --file specification.yaml
```
This command creates a group of three similar instances with the following characteristics:
- Named first-fixed-group.
- Running CentOS 7.
- In the default-net network.
- In the ru-central1-a availability zone.
- With a single vCPU and 4 GB RAM.
- With a 32 GB network HDD.

Use the API method create.