To enter and exit maintenance mode

~ # esxcli <conn_options> system maintenanceMode set --enable true

After all virtual machines on the host have been suspended or migrated, the host enters maintenance mode. You cannot deploy or power on a virtual machine on hosts in maintenance mode.

To exit maintenance mode

~ # esxcli <conn_options> system maintenanceMode set --enable false 

To poweroff the system, it must be in maintenance mode:

~ # esxcli system shutdown poweroff --delay=10 --reason=reboot

Stop the VM, then for each vmdk:

~ # vmkfstools -i /vmfs/volumes/Storage1/examplevm/examplevm-000003.vmdk /vmfs/volumes/Storage2/examplevm_clone.vmdk -d thin