The Update.State enumerated type defines the various states the appliance update can be in.
UP_TO_DATE : The appliance is up to date.
UPDATES_PENDING : A new update is available.
STAGE_IN_PROGRESS : The appliance update is in progress of downloading an update.
INSTALL_IN_PROGRESS : The appliance update is in progress of installing an update.
INSTALL_FAILED : The appliance update failed and cannot recover.
ROLLBACK_IN_PROGRESS : The appliance update failed and recovery is in progress.
Enumeration: UP_TO_DATE, UPDATES_PENDING, STAGE_IN_PROGRESS, INSTALL_IN_PROGRESS, INSTALL_FAILED, ROLLBACK_IN_PROGRESS,