How to Enable Maintenace Page (using redirect) on the Openstack Dashboard¶

Inside the OpenStack dashboard create the maintenance directory:
```
$ mkdir /var/www/maintenance/
```

Enter the maintenance directory and create an index.html that will be used as maintenance page:

 ------------
|  EXAMPLE   |
 ------------

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>
<head>
<meta http-equiv="Content-type" content="text/html;charset=UTF-8">
  <title>GARR cloud Maintenance</title>
  <style type="text/css">
    body { text-align: center; padding: 150px; }
    h1 { font-size: 50px; }
    body { font: 20px Helvetica, sans-serif; color: #333; }
    #article { display: block; text-align: left; width: 650px; margin: 0 auto; }
    a { color: #dc8100; text-decoration: none; }
    a:hover { color: #333; text-decoration: none; }
  </style>
</head>
<body>
  <div id="article">
    <h1>We&rsquo;ll be back soon!</h1>
    <div>
      <img width="100" src="GarrCloud.png" alt="GARR Cloud Logo" class="floating_element"/>
      <p>Sorry for the inconvenience but we&rsquo;re performing some maintenance at the moment. The running instances are unaffected. If you need to you can always contact us on <b>cloud-support AT garr.it</b>, otherwise we&rsquo;ll be back online shortly! </p>
      <p>&mdash; GARR cloud support</p>
    </div>
  </div>
</body>
</html>

Edit the file in /etc/apache2/sites-enabled/default-ssl.conf and after the line DocumentRoot /var/www insert the following code:

RewriteEngine on
#enable switch
RewriteCond %{DOCUMENT_ROOT}/enable-maintenance -f
#remove loop
RewriteCond %{REQUEST_URI} !^/maintenance*
#redirect
RewriteRule ^(.*)$ https://dashboard.cloud.garr.it/maintenance/index.html [R=302,L]

Create the configuration file /etc/apache2/conf-available/maintenance.conf as shown below:

Alias /maintenance /var/www/maintenance
<Directory /var/www/maintenance>
             Options Indexes FollowSymLinks MultiViews
             AllowOverride None
             Order allow,deny
             allow from all
</Directory>

Enable maintenance configuration:
```
$ a2enconf maintenance
```
Create an empty file named maintenance:
```
touch /var/www/enable-maintenance
```
Restart the Apache service:
```
$ sudo service apache2 restart
```