Where is the maintenance mode value in the database?

Question

I know the maintenance mode value used to be in the variables table, but in D8 that table is replaced by (or joined with) the config table, but I couldn't find any row with that name.

Where is it located now?

Answer 1

It's no longer a part of the config system; it's a part of the state system which is stored in the key_value table as a part of the state collection.

Answer 2

For Drupal 8 and 9:

First check the system.maintenance_mode value:

SELECT `value` FROM `key_value` 
WHERE `name` = 'system.maintenance_mode'

Then update the value:

UPDATE `key_value` 
SET `value` =   'b:0;'
WHERE `name` = 'system.maintenance_mode' AND `value` =  'b:1;'

Then empty all tables starting with "cache":

TRUNCATE `cachetags`;
TRUNCATE `cache_bootstrap`;
TRUNCATE `cache_config`;
TRUNCATE `cache_container`;
TRUNCATE `cache_data`;
TRUNCATE `cache_default`;
TRUNCATE `cache_discovery`;
TRUNCATE `cache_dynamic_page_cache`;
TRUNCATE `cache_entity`;
TRUNCATE `cache_menu`;
TRUNCATE `cache_page`;
TRUNCATE `cache_render`;
TRUNCATE `cache_toolbar`;

Answer 3

An alternative (depending on your use case) is to use drush:

drush sset system.maintenance_mode 0
drush cr