How to turn Magento 2 Maintenance Mode ON or OFF?

To enable maintenance mode you should create var/.maintenance.ip file. This file can contain a list of IP addresses. If an entry point is accessed using HTTP and the client IP address corresponds to one of the entries in that list, then maintenance mode is off.

Command usage::

bin/magento maintenance:enable
bin/magento maintenance:disable

To enable maintenance mode for all clients except 192.0.2.10 and 192.0.2.11:

bin/magento maintenance:enable --ip=192.0.2.10 --ip=192.0.2.11

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In order to put your Magento 2 store in maintenance mode, you need to create one .maintenance.flag file and upload it under var folder at root of your Magento 2 installation.

If var/.maintenance.flag does not exist, Magento operates normally, and maintenance mode is off.

More for information read this post

You can enable disable maintenance mode and exempt IP-addresses enable disable for using below command.

Maintenance mode Enable:

php bin/magento maintenance:enable

Maintenance mode Disable:

php bin/magento maintenance:disable

Maintenance mode Enable List of exempt IP-addresses

php bin/magento maintenance:enable --ip=192.0.3.26 --ip=192.0.4.27

Maintenance mode remove List of exempt IP-addresses

php bin/magento maintenance:disable --ip=none

Hope it help!