Moving a live site with minimal downtime
Abstract
This article will explain how to move a live and running site from one server to another with minimal downtime. Please note, that in order to follow you will need ssh permissions on both servers and high-level permissions (root) on the server to which you are transferring.
Overview of the procedure
When transferring a live site from one server (a shared hosting account for example) to another server (a VPS or dedicated) a major concern is downtime of the live website. In order for the website to get transferred you would need to copy the webite over to the new server and change the DNS pointers to the new server for the domain your website uses. For a static website this is as easy as that, but what if your website is dynamic and users can change database records and upload images to the website. A simple copy of the website will not work, because some images and database records will be lost.
To avoid this problem we are going to mount all the directories, that users are able to update using NFS and will allow network access to the mysql database from the old server.
For the example I will be using the debian operating system. You will be able to follow easily using other setups as well.
Preparing the new server
Ok, so you received a new server and now you need to prepare it for the website. I will not discuss the process f configuring Apache/PHP/MySQL or any other technology your website uses, as this is very user specific.
First you need to install the NFS tools. On Debian the packages you will need are nfs-server and nfs-client. You need to install them. After they are installed you will see, that an /etc/exports file appeared. This is where you will be adding mountable directories.
Let’s say I want to transfer a domain name example.com from the old server with IP of 62.62.62.62 and on the new server (63.63.63.63) I plan to use it at /home/admin/domains/example.com/public_html . Basically all the web-accessible files will be stored in the public_html directory.
I would recommend, for testing purposes to try and make this directory mountable and mount it on the old server. To do this add the following line to /etc/exports file
/home/admin/domains/example.com/public_html 62.62.62.62(rw,no_root_squash)
then type
/etc/init.d/nfs-kernel-server restart
Note, that your nfs restart script could be different.
This will allow the old server with IP 62.62.62.62 to mount the public_html directory.
Now, log in to the old server and mount this directory somewhere. I would like to mount it into /tmp/example.com
mkdir /tmp/example/com
mount 63.63.63.63:/home/admin/domains/example.com/public_html /tmp/example.com
At this point the folder will be mounted and ready. Now, you should put a maintenance notice on the website, so that users do not update it anymore while you are copying the website and the database to avoid any corruption of the system.
Start copying your website to the new server (copy the website to the /tmp/example.com directory. Since this is an NFS share it could take a while to copy, so use cp with -v parameter, so you could see the files being copied.
Database Copy
While the website is being copied you need to create a database dump on the old server. To do this simply login through the shell and type
mysqldump –user USERNAME –password DATABASE > database_dump.sql
This will dump all your data into the database_dump.sql file.
Copy this file to the new server using any method you prefer. Then on the new server type:
mysql –user USERNAME –password DATABASE < database_dump.sql
This will restore the database on the new server. It may take a long time to restore depending on your MySQL settings and the size of the database itself.
Enabling remote access to the new database server
By default MySQL does not allow remote connections and all users are created to be able to login only from the local server. To fix this you will need to grant all permissions to the database you use to the user, who could connect from the old server (62.62.62.62 in our case). To do this from the command line use:
grant all on DATABASE.* to USER@’62.62.62.62′ identified by ‘PASSWORD’
Now your old server can access the database at the new server.
Also, please check the mysql configuration file /etc/my.cnf or /etc/mysql/my.cnf and comment the line which says
skip-networking
otherwise you will not be able to use the networking at all with mysql.
Mounting updatable directories
Ok, so your website is now copied to the new server and you are ready to configure mountable directories.
Let’s assume, that in our case we have 1 updatable directory, which is images and it is in the root of the website.
You need to update the /etc/exports file with the following:
/home/admin/domains/example.com/public_html/images 62.62.62.62(rw,no_root_squash)
And commend out the other line we added previously to stop mounting the public_html folder and restart the nfs server.
Then go to the 62.62.62.62 server. I will assume, that the website was in /var/www/htdocs/example.com
You will need to type the following in order to mount the images directory:
mv /var/www/htdocs/example.com/images /var/www/htdocs/example.com/img_bkp
mkdir /var/www/htdocs/example.com/images
mount 63.63.63.63:/home/admin/domains/example.com/public_html/images /var/www/htdocs/example.com/images
Assign your permissions to the directory (depending on your setup you might need to change the owner of the directory as well).
Restarting the website and waiting
Now, you need to reconfigure the old website at 62.62.62.62 to use the new database server at 63.63.63.63. Configure the website respectively and fill in the username and password of the new mysql server and then remove the maintenance mode from the webite. It should continue working as normal, but the database and user updatable directories are now at the new server.
After this you can point the dns to the new server and once it propagates your website will be running off the new server. This usually takes 12-48 hours.
Tags: live site, moving, scaling, website transfer