[Solved]Snow Leopard (OS X 10.6.2) can’t boot after upgrading to 10.6.2

After upgrading to Snow Leopard (OS X) 10.6.2 from 10.6.1, I found that my system could not boot, no matter what option I chose at the boot prompt (-x, -v, -s etc). After trying for nearly half an hour, I was about to give up. Finally, I tried replacing the kernel and it rocked! I think I should share my solution here because I couldn’t find something like that on Google.

What I did:
Replacing the kernel of OS X 10.6.2 by OS X 10.6. You can find the old kernel from your backup (if you have), or from the Snow Leopard installation disk.


  1. Grab your OS X 10.6 installation disk.
  2. Boot the system using the external DVD-Rom or USB Flash Drive.
  3. After booting to the installation screen, select your language and continue.
  4. Open Terminal
  5. Type the following:
cp /mach_kernel /Volumes/XXX/

where XXX is the name of your system directory. If you are not sure how to find it, you can try to run:


Warning(Side Effect):
When the system upgrades to OS X 10.6.2, it upgrades both the kernel (the brain) and the apps (the body) to 10.6.2. Now, we are downgrading the brain back to 10.6. It may cause unexpected behavior because the brain and the body are speaking different languages. You can think about the problem this way: The brain is speaking an old language while the body understands the new language only. Will they get along together? May be. Only Apple knows the answer.

So do it at your own risk.

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Installing Apache on Snow Leopard (OS X 10.6)

The Apache web server comes with the OS X is a bit out dated. So I decided to install a new one. After I tried installing it using mac port, it kept giving error.

Finally, I built the Apache from source, and it worked!

Grep Apache from here.

Download the file, where the link should look something like:

Unix Source: httpd-2.2.14.tar.gz

Run the following command in terminal:

tar -zxvf httpd-2.2.14.tar.gz

cd httpd-2.2.14



sudo make install

That’s it! Now, let’s test the webserver.

First, let’s disable the Apache that shipped with the OS X (Not the one you just install!). You can simply do it by going to:

System Preferences -> Sharing -> Web Sharing

Go back to Terminal. Make sure the default web server is not running:

sudo apachectl stop

Now, let’s verify the installations:

/usr/local/apache2/bin/apachectl -v

You should see something like this:

Server version: Apache/2.2.14 (Unix)
Server built:   Oct 24 2009 20:53:45

Now, let’s start the web server:

sudo /usr/local/apache2/bin/apachectl start

Open your browsers and access to http://localhost/.
You should see something like:

It works!

Have fun!


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Does the most popular imply the best?

Today, I had a discussion with my co-worker on the best languages for web applications. While I argued that Perl, and Ruby performs better than PHP, my co-worker had an opposite opinion. He believed that PHP is the best language overall because it is widely used. It brings me to think of a question, does the most popular imply the best?

Let’s answer this question by examples:

Category Most Popular The Best Why The Best?
OS (Desktop) Windows OS X User friendly, secure, stability, and performance.
OS (Server) Linux, Windows Server FreeBSD Fast, stable, secure, simple design, and centralize management.
Browsers Internet Explorer, Firefox Safari Fast, secure, stable
Programming languages (Desktop/GUI) C#, Java C, C++ Fast, secure
Programming languages (Web/Server) PHP, ASP Ruby, Python, Perl Fast, fewer lines of code.
Database MySQL, Oracle Berkeley DB, Tokyo Cabinet Fast I/O, simple design, smaller size of the database file.
Software company to work for Microsoft Start-up Rewards, opportunity to grow

I think there are several reasons why the most popular things are not the best.

1. Most popular thing is always backed by the best marketing strategies. Marketing strategies is simply a way to let people know about the product and convince them to use it. It has nothing to do with the quality of the product at all.

Example: The ads of Internet Explorer 8 look very attractive. Is it the most secure browser ever?

2. Most people are followers. They are not good in selecting good products from bad products(i.e., filtering the noise). They believe that the choice form most people (most popular) should be the best one. This is similar to election. The choice of most people is more likely to be better.

Example: Is MySQL really the best database?

3. Different people have different preferences. So a popular product must have the general taste. For example, an extremely hot and spicy food may be better to the body, but it is not as popular as a mild one, because the number of people that can take extremely hot and spicy food is smaller.

Example: Linux is very easy to configure comparing to FreeBSD (GUI vs command line) from the end-user perspective, but it is less powerful and stable overall.


Think twice before your move.

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Performance Benchmark: FreeBSD vs Ubuntu vs OS X, which one is better?

If you cannot decide whether you should go with FreeBSD or Ubuntu (or Linux), check out this article: FreeBSD or Linux in 6 Simple Questions

Recently I am working on building a web farm which is formed by three ancient time computers (The sum of their ages is older than me). Therefore, I need to pick an operating system to make them running efficient enough. Basically here are my criterias:

  • It must be secure. (Sorry, Microsoft Windows, I tried installing Windows Server and the OS got infected by virus in 20 minutes after connecting to Web.)
  • It must be stable and require no reboot. (I have a very good experience with FreeBSD. My longest record of uptime is 6 months so far.)
  • It must be efficient and effective on performance.

So after trying different operating systems, I ran down to three choices: FreeBSD 8, Ubuntu 10 and OS X.

And I finally go with FreeBSD 8. Before I talked about why I kick the Ubuntu and OS X away, let me discuss what methodology I used.

First Test: Extreme Computation

I write a program to calculate the value of pi using Monte-Carlo simulations. For those who are not familiar with this simulation method, basically it try to repeat a calculation for n times and try to determine the value of pi based on the results of calculations. This calculation will use all available CPU resources.

Here is the result from a computer: Pentium II 400MHz + 160MB

  • FreeBSD 8.1 ~ 5 seconds
  • FreeBSD 4.11~ 10 seconds
  • Ubuntu 10.04 ~ 8 seconds
  • OS X 10.3.9 ~ 11 seconds

The result is very obvious, FreeBSD 8.1 is the best candidate in this test. However, the result of my program only gives a very small portion of the picture. So I decide to run another test:

Second Test: Apache Benchmark

No test is better than the real world test drive. Since my primary purpose is for web server, so I decide to test the performance on how Apache perform on different operating systems. My test is pretty simple, I basically ask the Apache Benchmark client to download a page from the test server. The page does three things:

  1. Display a picture
  2. Insert a record into MySQL database
  3. Retrieve the current count from MySQL database

This way I can test the overall performance on how the system handles the file I/O, database I/O and computations.

So the result is pretty interesting (1000 total requests and 100 concurrent requests)

  • FreeBSD 8.1 ~ 200 requests/sec, no failure
  • FreeBSD 4.11~ 150 requests/sec, approx. 20% failure.
  • Ubuntu 10.04 ~ 180 requests/sec, no failure
  • OS X 10.3.9 ~ 160 requests/sec, approx. 50% failure.

I am not surprised with the result because FreeBSD 8 really does a very good job in kernel optimization. Since kernel is the heart(or brain) of all computations, an OS with good kernel is expected to give good results always.

So, I finally pick FreeBSD 8 as the core OS of my web farm, and I am loving it.

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Installing Apache, PHP, MySQL and MemCached on OS X

This is my note on how to to install Apache, PHP and MySQL on a an OS X box. Although some of these applications are come with the operating systems, it is always good to know how to upgrade them to the latest version.

1. Apple Developer Tools and Mac Port

Before installing Mac Port, you will need the Apple Developer Tools. You can download it from the Apple Developer’s Network.

After installing Apple Developer’s Tools, you can install Mac Port. You can get it from the here.

Update Mac Port

sudo port selfupdate

Add the Mac Port path in the profile: ”’~/.bash_profile”’:

export PATH=/opt/local/bin:$PATH

MySQL:Mac Port
Install MySQL from Mac Port:

sudo port install mysql5

Go to the [http://dev.mysql.com/downloads/mysql/5.0.html#macosx-dmg MySQL’s website] to download the package.

Setup the a master password for root user:

/usr/local/mysql/bin/mysqladmin -u root password 'new-password'

Add the MySQL path in the profile: ”’~/.bash_profile”’:

export PATH=/usr/local/mysql/bin:$PATH

Apache:Mac Port

Install Apache from Mac Port:

sudo port install apache2

Open the configuration file: ”’/opt/local/etc/rc.conf”’ and add the following at the end of the file:


PHP:Mac Port

Install PHP from Mac Port:

sudo port install php5 +apache2 +mysql5 +pear 

When that is done, register PHP 5 with Apache 2:

cd /opt/local/apache2/modules
sudo /opt/local/apache2/bin/apxs -a -e -n "php5" libphp5.so

And create a php.ini file (which you can edit to configure PHP 5):

sudo cp /opt/local/etc/php.ini-dist /opt/local/etc/php.ini


Edit the Apache configuration file ”’/opt/local/apache2/conf/httpd.conf”’ and add the following lines to the end of the file:

AddType application/x-httpd-php .php
AddType application/x-httpd-php-source .phps

Replace this line:

DirectoryIndex index.html

by the following:

DirectoryIndex index.php index.html


If the MySQL is installed from package rather than from Mac Port, we need to modify the mysql.default_socket value.

Open ”’/opt/local/etc/php.ini”’:

mysql.default_socket = /tmp/mysql.sock


Install MemCached from Mac Port:

 sudo port install memcached
 sudo port install php5-memcache

We need to enable MemCached in PHP5.

First, we need to add the following in ”’/opt/local/etc/php.ini:”’:

extension = memcache.so

Run the following command to start MemCached:

sudo /opt/local/bin/memcached -d -u nobody

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