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gcloud compute instance-groups managed abandon-instances

NAME
gcloud compute instance-groups managed abandon-instances - abandon instances owned by a managed instance group
SYNOPSIS
gcloud compute instance-groups managed abandon-instances NAME --instances=INSTANCE,[INSTANCE,…] [--region=REGION     | --zone=ZONE] [GCLOUD_WIDE_FLAG …]
DESCRIPTION
gcloud 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
These variants are also available: 
gcloud alpha compute instance-groups managed abandon-instances
 
gcloud beta compute instance-groups managed abandon-instances
 
gcloud preview compute instance-groups managed abandon-instances