gcloud alpha compute instance-groups managed abandon-instances

NAME: gcloud alpha compute instance-groups managed abandon-instances - abandon instances owned by a managed instance group
SYNOPSIS: gcloud alpha compute instance-groups managed abandon-instances NAME --instances=INSTANCE,[INSTANCE,…] [--region=REGION | --zone=ZONE] [GCLOUD_WIDE_FLAG …]
DESCRIPTION: (ALPHA) gcloud alpha compute instance-groups managed abandon-instances abandons one or more instances from a managed instance group, thereby reducing the targetSize of the group. Once instances have been abandoned, the currentSize of the group is automatically reduced as well to reflect the change.
Abandoning an instance does not reboot or delete the underlying virtual machine instances, but just removes the instances from the instance group. If you would like to delete the underlying instances, use the delete-instances command instead.
The command returns the operation status per instance, which might be FAIL, SUCCESS, or MEMBER_NOT_FOUND. MEMBER_NOT_FOUND is returned only for regional groups when the gcloud command-line tool wasn't able to resolve the zone from the instance name.
For a more detailed overview of how abandoning instances from a managed instance group works, see Abandoning instances from a MIG.
POSITIONAL ARGUMENTS: NAME

Name of the managed instance group to operate on.
REQUIRED FLAGS: --instances=INSTANCE,[INSTANCE,…]

Names of instances to abandon.
OPTIONAL FLAGS: At most one of these can be specified:

--region=REGION

Region of the managed instance group to operate on. If not specified, you might be prompted to select a region (interactive mode only).
A list of regions can be fetched by running:
gcloud compute regions list

Overrides the default compute/region property value for this command invocation.

--zone=ZONE

Zone of the managed instance group to operate on. If not specified, you might be prompted to select a zone (interactive mode only).
A list of zones can be fetched by running:
gcloud compute zones list

Overrides the default compute/zone property value for this command invocation.
GCLOUD WIDE FLAGS: These flags are available to all commands: --access-token-file, --account, --billing-project, --configuration, --flags-file, --flatten, --format, --help, --impersonate-service-account, --log-http, --project, --quiet, --trace-token, --user-output-enabled, --verbosity.
Run $ gcloud help for details.
NOTES: This command is currently in alpha and might change without notice. If this command fails with API permission errors despite specifying the correct project, you might be trying to access an API with an invitation-only early access allowlist. These variants are also available:
gcloud compute instance-groups managed abandon-instances

gcloud beta compute instance-groups managed abandon-instances