Recently, because of a mandatory VPS move I had an opportunity to migrate all my sites from apache to nginx. My old box was in a messy state and setting up a new box from scratch was always going to be fun. Here in this post, I will walk you through all the steps that helped me migrate seamlessly. Specially, how did I setup the new box ensuring zero downtime on the sites.

Ensuring zero downtime while migration:
By the time I will pin up various pieces on my new vps box, I didn’t want my site visitors to see an under-maintenance page. To ensure zero downtime, I usually follow these steps:

• Setup the new vps with nginx, php-fastcgi, etc as described later in the post
• To verify the setup on new vps, edit the local host file depending upon your operating system

  /private/etc/hosts (mac)
  /etc/hosts (ubuntu)
  C:WindowsSystem32driversetchosts (windows)
  

  Go ahead and add the following host entry:

  99.198.122.216 abhinavsingh.com

  where, 99.198.122.216 is my new vps ip address and abhinavsingh.com is a vhost configured to handle by nginx on my new vps

• Now, whenever I visit http://abhinavsingh.com in my browser, my local machine will point it to my new vps box. However, all other visitors will still be served by apache on old vps.
• After verifying the setup, I simply remove previously added host setting on my local box and update the DNS settings for my site at godaddy.

To start with, just add up the required host setting on your local system.

Installing Nginx and configuring vhosts:
Follow these steps to install nginx webserver:

• Update and upgrade apt-get and install nginx

  sudo apt-get update
  sudo apt-get upgrade
  sudo apt-get install nginx

• Configure vhost for nginx by creating a file /etc/nginx/sites-available/mysite.com as follows:

  server {
          listen   80;
          server_name  mysite.com;
          access_log  /var/log/nginx/mysite.access.log;
  
          root   /var/www/mysite;
          index  index.php index.html index.htm;
  
          location / {
          }
  }

• Enable vhost by creating a symlink as follows:

  cd /etc/nginx/sites-enabled
  ln -s /etc/nginx/sites-available/mysite.com mysite.com
  sudo /etc/init.d/nginx restart

• Assuming you have configured your local host file correctly, try visiting http://mysite.com and your browser will take it to the new vps

Setting up php-fastcgi and xcache:
Here are the steps to configure php-fastcgi and how to ensure php-fastcgi is up and running even after system reboot. We will also configure xcache for better performance.

• sudo apt-get install php5-cgi php5-cli php5-xcache
• Download php-fastcgi default config and place it at /etc/default/php-fastcgi
• Download php-fastcgi init.d script and place it at /etc/init.d/php-fastcgi
• Add php-fastcgi init.d as startup script

  update-rc.d -f php-fastcgi defaults

• Update following fields inside /etc/php5/conf.d/xcache.ini:

  xcache.admin.user = "admin"
  xcache.admin.pass = "pass"
  xcache.size  =  128M
  xcache.count = 4

  xcache.count should ideally be equal to cat /proc/cpuinfo |grep -c processor

• Setup xcache admin interface:

  cd /var/www
  ln -s /usr/share/xcache/admin xcache

• Update /etc/php5/cgi/php.ini as per your requirements and start php-fastcgi process

  sudo /etc/init.d/php-fastcgi start

• Visit xcache admin panel http://vps_ip_address/xcache

Stitching php-fastcgi and nginx vhosts:
Now lets enable php for vhosts configured with nginx:

• Download nginx fastcgi param config file and place it at /etc/nginx/fastcgi.conf
• Update /etc/nginx/sites-available/mysite.com with following config:

  location ~ .php$ {
                  fastcgi_pass    127.0.0.1:9000;
                  fastcgi_index   index.php;
                  fastcgi_param   SCRIPT_FILENAME /var/www/mysite$fastcgi_script_name;
                  include         /etc/nginx/fastcgi.conf;
          }
  

• Restart nginx and we are done

Here we complete the vps setup and vhost configurations. Verify the new vps setup and once satisfied update site’s DNS settings. Another challenge involving migration from apache to nginx includes rewriting apache .htaccess rewrite rules for nginx. However, I will keep that for another post.