The updates to your Chrome OS are based on your company’s corporate device policy. We recommend you use the Google Admin Panel to configure Chrome OS to update automatically. The update channel should always be set to Stable to ensure optimal functionality. Inside this panel, updates can also be set to run during off-peak hours when the device is not in use. This will allow any critical updates, bug fixes, and new features to be installed on the system.
To perform the update:
Open Google Admin > Device Management > Chrome Management
Chrome management will allow administrators to customize update settings such as only updating Chrome OS to stable versions and to set update schedules for different groups.
For more information please see the Google article found here.