As an administrator, you can put the site into Maintenance mode via the System Confugration.
This will redirect any page request to the maintance page except the following routes
- Sign In
- Sign Out
This is necessary because as an administrator you still need to be able to sign in in order to uncheck the option again.
Disable Maintenance Mode
Sign in as an administrator. Go to the System Configuration and uncheck the “Under Maintenance” switch, then click Apply .