htaccess: how to redirect all pages to a holding page

I have to put a site down for about half an hour while we put a second server in place. Using .htaccess, how can I re开发者_如何学Cdirect ANY request to domain.com to domain.com/holding_page.php?

Options +FollowSymlinks
RewriteEngine on
RewriteCond %{REQUEST_URI} !/holding_page.php$ 

RewriteRule $ /holding_page.php$l [R=307,L]

Use 307 (thanks Piskvor!) rather than 302 - 307 means:

The requested resource resides temporarily under a different URI. Since the redirection MAY be altered on occasion, the client SHOULD continue to use the Request-URI for future requests.

As I came across this problem, here is the solution I used (brief explanations in the comments):

RewriteEngine On
RewriteBase /

# do not redirect when using your IP if necessary
# edit to match your IP
RewriteCond %{REMOTE_ADDR} !^1\.1\.1\.1

# do not redirect certain file types if necessary
# edit to match the file types needed
RewriteCond %{REQUEST_URI} !\.(jpe?g?|png|gif|css)

# this holding page that will be shown while offline
RewriteCond %{REQUEST_URI} !^/offline\.html$

# use 503 redirect code during the maintenance job
RewriteRule ^(.*)$ /offline.html [R=503,L]
ErrorDocument 503 /offline.html

# bots should retry accessing your page after x seconds
# edit to match your maintenance window
Header always set Retry-After "3600"

# disable caching
Header Set Cache-Control "max-age=0, no-cache, no-store"

Besides the additional conditions and headers, the main idea is to use a 503 status code when you are doing a maintenance job.

The 503 code stands for Service Unavailable, which is exactly the case during the maintenance. Using this will also be SEO friendly as the bots won't index the 503 pages, and they will come back later-on after the specified Retry-After to look for the actual content.

Read more details here:

• Use a 503 HTTP status code (from a person who worked at Google) - https://plus.google.com/+PierreFar/posts/Gas8vjZ5fmB
• Redirect Site to Maintenance Page using Apache and HTAccess - http://www.shellhacks.com/en/Redirect-Site-to-Maintenance-Page-using-Apache-and-HTAccess
• HTTP 503: Handling site maintenance correctly for SEO - https://yoast.com/http-503-site-maintenance-seo/

This works better...

Options +FollowSymlinks
RewriteEngine on
RewriteCond %{REQUEST_URI} !/holding_page.php$ 
RewriteRule $ /holding_page.php [R=307,L]