Drupal-powered websites can be put into an “offline mode.” This is much better than most alternatives (such as taking the web server offline), especially for search engines, as the message and HTTP status codes given to users and robots alike will tell them to patiently come back later.
I’ve found that putting the site into offline mode makes database backups go much faster on heavily trafficked sites (which is obvious). However, for a particular site I was working with, this needed to be done in an automated manner, and on a dedicated database server that did not have access to the Drupal installation.
Most people take their Drupal sites offline through Drupal’s web-based administration interface. They can also be put offline through the Drupal Shell. Neither were suitable for me: the former cannot be automated easily, and the latter requires access to the Drupal installation. Fortunately, Drupal sites can easily be taken offline by setting things in the database, which can easily be done via bash scripts and the command-line MySQL client.
Given your database user is my_db_user, password my_password, and database my_drupal_db, the backup script would look something similar to:
\#!/bin/bash \# Take site offline mysql --user my_db_user --password=my_password my_drupal_db << EOF UPDATE variable SET value='s:1:"1";' WHERE name = 'site_offline'; DELETE FROM cache WHERE CID = 'variables'; EOF \# Do stuff here while the site is offline (e.g. backup) \# Bring site online mysql --user my_db_user --password=my_password my_drupal_db << EOF UPDATE variable SET value='s:1:"0";' WHERE name = 'site_offline'; DELETE FROM cache WHERE CID = 'variables'; EOF
Update: The original version of this article had some problems on some setups with the variables table being cached. I added another SQL statement to make sure this cache is flushed so the site actually reflects its configuration.
Update: This method really doesn’t work that well, and the more I think about it, there isn’t a way to get around writing something that interacts with Drupal. I’m working on a script that will be more fool-proof.