The partition currently in control of the boot process is the active partition, the other partition is the inactive partition with the alternate image. Use this command to manually change the next boot partition or image.
boot system [active|inactive|primary|secondary] {on <DEVICE-NAME>}
      boot system [active|inactive|primary|secondary] {on <DEVICE-NAME>}
         | system [active|inactive|primary|secondary] | Specifies the image used by the device to boot up 
 Note: You will need to
                           reload the device in order for the change to take effect. | 
| on <DEVICE-NAME> | Optional. Changes the next boot image or partition on a specified
                           device 
 Note: If no device is
                           specified, the logged device's next boot-up configuration is
                           changed. | 
ap510-133B38#show boot
--------------------------------------------------------------------------------
     IMAGE            BUILD DATE             INSTALL DATE          VERSION
--------------------------------------------------------------------------------
  Primary       12/06/2019 20:11:39     11/13/2019 06:30:58     7.3.0.0-037R
  Secondary     11/21/2019 17:49:55     11/20/2019 12:26:01     7.3.1.0-001D
--------------------------------------------------------------------------------
Current Boot       : Secondary
Next Boot          : Secondary
Software Fallback  : Enabled
ap510-133B38#
         ap510-133B38#boot system primary Updated system boot partition ap510-133B38#
ap510-133B38#show boot
--------------------------------------------------------------------------------
     IMAGE            BUILD DATE             INSTALL DATE          VERSION
--------------------------------------------------------------------------------
  Primary       12/06/2019 20:11:39     11/13/2019 06:30:58     7.3.0.0-037R
  Secondary     11/21/2019 17:49:55     11/20/2019 12:26:01     7.3.1.0-001D
--------------------------------------------------------------------------------
Current Boot       : Secondary
Next Boot          : Primary
Software Fallback  : Enabled
ap510-133B38#