i need to put my site into maintenance mode when some work is being done on the app servers.
add this rewrite to all vhosts that need to be taken down. When the switch needs to happen, create /system/maintenance.html
delete the file, or rename it when the maintenance is finished.
RewriteCond /system/maintenance.html -f
RewriteRule ^.*$ /system/maintenance.html [L]
this solution will cause all your images/js/css files to redirect to the maintenance page. Modify the regex if that is a problem, otherwise, dont use any image/js/css on the maintenance.html page.