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How to migrate your Linux Web site to another hosting company The Web site hosting business has become more competitive in recent
years. If you can find a better hosting deal, you may be able to save money
by switching hosting providers. But what's the best way to move your Web
site? What if you have a virtual private server (VPS) hosting several
domains? What about PHP and your SQL data? The thought of moving may be
daunting, but moving servers is not difficult if you plan properly. Here's
how.
A complete migration involves transferring the site data itself, meaning all
the HTML and possibly PHP and MySQL files and CGI programs. You also need to
modify the Domain Name System (DNS) information for the site and for the
routing of the site email. DNS holds information that translates IP
addresses to human-readable domain names. For Web site migration, the two
important DNS records are the address (A) record, which tells the browser
the IP address of the Web server, and the mail exchange (MX) record, which
tells mail servers how to route the email.
When you migrate your Web site to another hosting provider, you need to
update DNS to point browsers to the new location of your site. However, it
can take as long as 48 hours for DNS updates to propagate to all DNS servers
on the Internet. Part of your planning will be how to deal with that delay.
Often your domain name has been registered via a third-party domain name
registration company. When you move the site, your domain name company
remains the same, and only your Web hosting company changes. If your domain
name originaly came with hosting, you may need to contact your old hosting
company to see if you can separate the hosting package from the domain name.
The keys to a successful move are planning and preparation. Before the move
you should warn your users or customers of the forthcoming upgrade. Prepare
a "server down for upgrade" page for your old site. Note the IP addresses of
your new and old servers; these will come in handy when DNS is still in
flux.
Decide when to upgrade, meaning when your server is least busy. If you have
site statistics, use those to determine the best time. To reduce down time,
it is best to make the DNS changes several hours before you actually move
the domain. As long as your mail server is running on the new server, you
won't lose any email messages. If you have a static site, you can copy over
the data before you switch DNS and no one will ever know your hosting
provider changed. For a dynamic site you can out a skeleton site on your new
server until you make the full move.
The DNS changes you need to make involve updating the MX and A records to
point to your new server. To do that, you need to access the control panel
provided by the domain name registration company from which you obtained
your domain name.
The new MX record will need to point to the new server. Like A records, MX
records can take a while to propagate through the Internet. To avoid mail
loss you will need to check your old mailbox at least once a couple of days
after the move. You will also need to use the IP address of the old mail
server rather than its domain name, as you won't be able to rely on
mail.domain.com to check the old mailbox, as that will point to your new
server. Depending on how much control you have of your old server, you could
shut down the mail server after modifying the MX records, in which case
incoming mail would queue up until the new mail server is running, at which
point it would be delivered without problems.
Once you've handled the DNS information, it's time to tackle the data
itself. HTML and PHP files aren't hard to move; just use a good FTP program
and copy the data from one server to the other. If you have SSH access to
both of the servers you can copy the files directly. If you don't, you will
have to download the files to a local machine and then upload them to the
new server.
Moving databases is a bit more complex. Assuming you are using MySQL, there
are several ways to copy over the data. One is to do a dump of the data into
a file and then copy that file to the new server and populate the new
database. To do this you use the mysqldump command:
$ mysqldump -p -u username mydatabase > mydata.sql
Once copied onto the new server your can populate your new database with the
mysql command:
$ mysql -p -u username mydatabase < mydata.sql
If you don't have SSH access to your servers you won't be able to use these
MySQL commands, but you can still use a tool such as phpMyAdmin that handles
MySQL administration over the Web. phpMyAdmin has excellent dump and restore
features, though for the restore there is a maximum upload file size of
2,048KB. You can use compression to maximize your chances of squeezing all
of your data into 2MB. [what if you have more than 2MB, as many of our
readers will? - Lee, I have altered the next paragraph to clarify this]
If you lack SSH access and you have too much data for phpMyAdmin to handle,
look into a MySQL synchronization tool called SQLyog Job Agent (SJA).
If all else fails you will need to ask the support team of your old hosting
company to dump your database for you. Then you will need to ask the support
team of your new hosting company to populate the new database.[Lee, I have
added this paragraph in case readers don't have ssh, can't use phpMyAdmin
and can't use SJA.]
If you have a site with dynamic data, such as an e-commerce site, you need
to make special provisions for the DNS update delays. As the DNS changes
propagate through the Internet some people will see your new site and others
your old. This could cause problems for you. Imagine a customer placing an
order on your old site after you have moved all the data over to your new
site.
There are two [different] ways you can deal with this problem. [Lee, this is
an either-or] First, stop taking orders on the old site once you have
started the move. At the checkout stage display a polite notice asking
customers to come back in a couple of hours, after which they should be
taken to the new site. If you don't have that kind of control over your site
then the best thing is to close down the old site by replacing its
index.html with a notice saying the server is down for upgrades and will be
back soon. An alternative solution is to use a synchronization tool like SJA
to make sure any changes made on the old site get propagated to the new one.
Finally, watch out for incompatibilities between the software on your old
server and that on the new. Try to make sure that any difference in versions
of crucial software like MySQL and PHP won't cause any problems.
If you host a VPS installation then you probably have several domains to
migrate. The problems are the same, but there is more work to do. If you
have a VPS you should warn your customers in plenty of time about the
upcoming move. Call it a server upgrade, as this will cause less worry.
An advantage of having a VPS is that you have more control of your sites.
You probably have SSH access and you can do things like shutting down the
mail server during the transition. However, if you are hosting domains for
others, then there is the problem of passwords. When you move to the new
server you will need to re-create domains and user accounts, but you won't
have access to the passwords set by your customers. Generally you will need
to issue your customers new passwords. Again, plenty of advanced warning
will help ease the pain.
If your VPS uses Plesk 7 Reloaded then migration becomes a lot easier. This
software includes a great (though still experimental) tool called the
Migration Manager that supports migrating from remote servers using Plesk
2.5.x, 5.x, 6.x, and 7.x, as well as Confixx 2, Ensim 3.5.x, and cPanel 9.
To use the Migration Manager you need to enter the remote host address (it
is best to use the IP address), the login name (normally root) and the
password. After that you set the remote system type (Plesk, cPanel, etc.)
and click Next. The Migration Manager will then send an agent to the remote
server and offer you a list of domains and clients on the remote server. If
you migrate a client it will bring over the client data (like username and
password) and all the domains belonging to that client. If you import a
domain you will have to have a client account ready on the new server to
take ownership of the imported domain.
Although experimental, for standard cases Migration Manager should work
well. In a recent real-life migration, 95% of the domains [I moved for a
client] migrated without a problem. There was one domain that had more than
100 subdomains that failed; They had to be copied over by hand!
When moving servers you need to keep downtime to a minimum. If you plan
properly your users may not even notice that you have switched servers. If
possible, perform a trial run of the actual move. No one will see your new
site because you won't update DNS yet. To enable you to see your new site,
edit the /etc/hosts file on your client and add your domain name (including
the www) with the new IP address. You should also restart your browser.
Don't forget to remove this entry when you have finished experimenting.
About the Author
Gary Sims has a degree in Business Information Systems from a British
university. He worked for 10 years as a software engineer and is now a
freelance Linux writer and
founder of Low Price Hosting
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