Linux Server Security, Second Edition

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

246

|

Chapter 8: Database Security

Starting with MySQL 4.0.3, many variables can be changed at runtime without

restarting the server. See http://dev.mysql.com/doc/mysql/en/Dynamic_System_

Variables.html.

Database Operation

Now that you’ve installed a reasonably secure version of the server in a reasonably

secure location, let’s look at how to run the thing securely.

MySQL Table Types

Many new developers of MySQL-backed web sites have been horrified to watch their

database fall over and sink into the swamp just as their site becomes popular.

Although MySQL has a reputation for speed, this is primarily in cases where data-

base reads greatly outnumber writes. Once the number of simultaneous writes

crosses some threshold, performance degrades most ungracefully.

This is a self-inflicted Denial of Service by the implementation of the default MySQL

table type: MyISAM. It locks the whole table with each write (INSERT, UPDATE, or

DELETE), pushing back all other requests. It’s like closing all check-in lines but one

at a busy airport terminal. Waits lengthen until the administrator must kill database

threads or restart the database server.

MySQL actually has multiple table types, each implementing a different storage

mechanism and behavior. You’ll usually deal with two: MyISAM and InnoDB.

MyISAM