You can use either esxcli or vicfg-hostops to enter/exit maintenance mode.

esxcli

• Enter: esxcli system maintenanceMode set --enable true
• Exit: esxcli system maintenanceMode set --enable false

vicfg-hostops

• Enter: vicfg-hostops --operation enter
• Exit: vicfg-hostops --operation exit

Note that you can use vicfg-hostops --operation info to check whether the host is finished with entering maintenance mode or is still busy.

PowerCLI

After connecting to the host or vCenter server:

• Enter: Get-VMHost <name-of-host> | Set-VMHost -State Maintenance
• Exit: Get-VMHost <name-of-host> | Set-VMHost -State Connected