Migrating from one dedicated linux server to another?

My suggestion is to take backups of everything and restore it on the new server. Ie:

1. Dump databases and restore them on the new server
2. Copy webserver, database, email configs on the new one

Of course it requires a little downtime. There are some things you can do to make the downtime smaller:

1. Do a previous rsync for all email data, then after everything configured and tested stop the service on the old server, rsync only the new data and start the new server.
2. Use mysql replication to keep data on both servers until the time to 'switch'
3. The rsync approach can be used with all other data (even db, but I suggest you to use a dump or replication to minimize the choice of error).

Also remember that this is a procedure that needs to be carefully planned and executed or data loss may happen.

You may be interested in exploring the possibility to use FSArchiver, http://www.fsarchiver.org/Main_Page

A few relevant things I've learned by trial and error (mostly error):

• Document the steps as you go so you have a record the next time you do it (there will always be a next time). That way you won't forget any steps and it permits someone else to do it as well.
• If you can switch components piece by piece it will be easier to diagnose issues. For example, keep the mail/database on the original server and just move the web server to the new server. Skip this if your application cannot easily handle inter-server but it is something to consider if you need to scale your system to multiple servers. This method is particularly useful if you need to minimize downtime.
• I wouldn't try just copying the raw database files from one server to another unless you are sure the database supports it. If you just have a few 100MB of databases I would just create a dump on the old server and restore on the new one. For larger databases it will be significantly quicker to setup replication.
• If using rsync or scp to copy files from one server to another make sure the user you use has read permissions for all the files. For example, I once used rsync to copy over some files from /etc but didn't have read permissions for some files. By the time I found out some files were missing it was too late (the old server was wiped). Since then I have always used tar as root on the old server to backup directories and then rsync/scp the tar archive over.