Monthly Archives: April 2009

MySQL: how to deny remote client access to MySQL temporarily

Say, you’re going to do a “dump” and you don’t want remote clients to alter the current data…

Here’s a simple trick to deny access to remote clients temporarily.

1. open your MySQL configuration file, my.cnf (in CentOS / Red Hat, located in /etc/my.cnf)
2. add skip-networking flag under [mysqld], like this:

[mysqld]
skip-networking

3. restart your MySQL server (in CentOS / Red Hat, run service mysqld restart)
4. Do a simple test to verify.

Note that this will affect remote clients only, local clients can still connect via Unix sockets.

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MySQL: 32-bit vs 64-bit OS

This is a classic mistake in deploying MySQL servers in stand-alone machines, deploying it in a >3GB memory 64-bit capable machine with a 32-bit linux OS. It’s quite an epidemic actually that even hosting sites are committing this “mistake”. It’s no surprise that even us suffered the same fate in our previous MySQL servers… (we have a valid reason though)

What’s wrong with 32-bit, you say?

Simply put, MySQL won’t be able to use the remaining memory at all. MySQL is a single process, 32-bit + single process = memory limit for each process is… sounds familiar?

Anyway, you can find more information from this blog [mysqlperformanceblog.com].

If you want to check if you have a 64-bit capable cpu, you can check the links below:
http://processorfinder.intel.com/
http://www.cpuid.com/

Just look for the AMD64 or EM64T flag.