Fedora Linux 12 is out today

Fedora Linux 12 is out today.

Here are the links to download Fedora 12:

  1. Download Fedora 12 64-Bit
  2. Download Fedora 12 32-Bit
  3. Download Fedora 12 PowerPC
  4. All versions

Suggestions:
I found that the downloading speed varies depends on which mirror you get. I suggest to test the download speed first, and re-try it (using a different mirror) if the speed is too slow.

For example, run the following command in terminal:

wget http://download.fedoraproject.org/pub/fedora/linux/releases/12/Fedora/x86_64/iso/Fedora-12-x86_64-DVD.iso

Which will show you the speed. Simply terminate the command and re-try it if the speed is too low.

Have fun with Fedora 12.

–Derrick

Our sponsors:

[Solved]Cisco RVS4000 4-port Gigabit Security Router – Slow

Recently we bought a Cisco RVS4000 4-port Gigabit Security Router and we noticed that the connection speed to the Internet was extremely slow. If we connected the server directly to the Internet (Without going through the Router), the download speed was around 80MBps, while the speed dropped down to 30 ~ 40MBps with the router with the default setting.

After disabling the IPS, the problem was gone!

Steps (IPS)- Required

  1. Go to the control panel (http://192.168.1.1)
  2. Go to the IPS tab
  3. Go to the Configuration Tab
  4. Disable the IPS function

Cisco RVS4000 4-port Gigabit Security Router - Slow Speed

Steps (Firewall) – Optional

  1. Go to the Firewall Tab
  2. Enable Firewall, DoS Protection and Block WAN Request
  3. Disable the rest

Cisco RVS4000 4-port Gigabit Security Router - Slow Speed

Looks like the IPS feature took too much resource from the router CPU.

–Derrick

Our sponsors:

Updated: What technologies (or toys) I am playing recently?

Recently I am playing the following technologies (toys):

  1. Tornado Web – Not sure how long will Apache + PHP last. Time to learn Python.
  2. Tokyo Cabinet & Tyrant – Another one of my long term plans to step away from SQL.
  3. PHP API for Tokyo Tyrant — I decide to write my own because I cannot find a good one.
  4. Moving my development platform from Windows to FreeBSD. My servers have been already on FreeBSD for many years. I think now is a good time to move my desktop systems to FreeBSD as well. Why not Linux? Oh Well…
  5. LUA – I may pick up Lua if time is permitted.

Looks like I will have a busy time other than shoveling the snow this Winter.

–Derrick

Our sponsors:

[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.

Steps:

  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:

df

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.

Our sponsors:

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

./configure

make

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!

–Derrick

Our sponsors:

It’s a pain to use Godaddy.com’s coupon!

Godaddy.com was running a sale today: $1.99 a domain name (Coupon Code: GEO199, no other purchase is necessary) for the first year. This is a very good deal so I decide to grab four domains from them. The pain began:

1. I couldn’t use the coupon code for four domains in the same order…

» Fine. I split the order into four. I didn’t have any problem on my first order.

2. I couldn’t use the coupon code on the same user account…

» Fine. I registered a new user account and tried again.

3. I couldn’t use the coupon code on the same browser…

» Fine. I cleaned up the cache and tried again.

4. I couldn’t use the coupon code from the same IP…

» Fine. I tried using a different IP…

5. I couldn’t use the coupon code with the same credit card…

» Fine. I tried using a different credit card…

6. Finally, I got four domains for $7.96. It’s a good deal but it already spent me half an hour.

Our sponsors:

Can’t send mail from Fedora Linux … Solved!

I was having problem today to send out an email from my Fedora 11 Linux box. By default, the mail server software, Sendmail, comes with the standard installation and no configuration is required. I didn’t understand why the Sendmail didn’t work.

After a very detail investigation, I finally found out why. Here are the steps I went through to solve the problem.

1. Make sure the Sendmail is running.

netstats -na | grep LISTEN

You should see something is running on port 25.

2. Make sure the stupid SELinux Firewall is disabled.

3. Make sure the Linux Firewall allows port 25.

4. Try to connect to the port 25.

telnet localhost 25

If you have trouble to connect to the port, that means something is not work.

5. Make sure you are not blocking port 25 at the system level:
In /etc/hosts.allow

sendmail: localhost: allow

That should work!

Our sponsors:

The Flying Saucer Balloon at Colorado

Why no one thought about taking a picture of the flying balloon using infra-red camera? The Raytheon one should do the work.

Click here to read the ridiculous story.

Our sponsors:

Area-Proportional Venn Diagram Tools

I was looking for tools to draw area-proportional Venn Diagram, but most of them either do not work in some cases or very difficult to use. Finally, I found a very very good one!

A very very nice tool to draw Area-Proportional Venn Diagram:
Area-Proportional Venn Diagram

http://bioinforx.com/free/bxarrays/venndiagram.php

I can also edit the Venn Diagram including labels, size and positions:
VennDiagram-02

So far this is the best I found on the web.

Our sponsors:

Interviewing a software engineer / developer / programmer

I am going to have a face-to-face interview with a candidate of a PHP programmer position this afternoon. I was told to prepare some technical questions for the interview.

If a candidate earns an face-to-face interview opportunity, that means his resume should have a very good match to the position requirement. However, people can put anything on their resumes, there is no way to tell whether the information on the resume is true or not (and referencees guarantee will give you good feedback on the candidates). That’s why a face-to-face interview is really important.

I will have around 30 minutes to 1 hour to interview a candidate, how can I get the most information from him to help myself making this decision?

After googling on the web, I found tons of information about how to interviewing a programmer, but most of them are related to really technical questions, such as “How do you solve this math puzzle?”, or “What’s the meaning of double-dollar variable in PHP?” etc. I think these questions are not efficient and effective enough to judge the skill of the candidates. Personally, I don’t like these types of questions at all because I think it does not help to judge a realistic performance of a person. I prefer some more realistic questions.

So, I end up designing a test by myself. It is nothing more than a simple html form (e.g., a form to update users’ contact information). The candidate will be asked to implement the functions to update the records. I think this is pretty closed to what I do in my work, i.e., Create, View, Update and Delete record.

Well, this question sounds pretty simple, and I think there are plenty of hidden traps. Here are what I expect in the codes:

  • Core function, i.e., Updating the record – 40%
  • Validating the inputs(e.g., don’t store a negative number into age column, make sure the ID exists etc) – 10%
  • Performance (e.g., Update the record only if the records have been changed by the users.) – 10%
  • Handling simultaneous update (e.g., lock the record before update) – 10%
  • Security (e.g., storing the configuration out of the web server scope, prevent online attack etc) – 10%
  • Development time(e.g., spending 2 hours ends up with very few features is not acceptable) – 10%
  • Think outside the box(e.g., Suggesting to use Ruby on Rails to shorten the development time, using jQuery for client-side validations etc.) – 10%

I believe that if a person can do great in a simple task, he will do great in a complex task. Unfortunately, it is not easy to look for a good programmer.

Updates (August 31, 2009):

The answers I received from the candidates are pretty interesting and filled with tons of surprise. Some of the answers go beyond my imaginations. Here are few examples:

  • One candidate sent me a package with all of the source codes. Unfortunately, none of the codes works. Apparently, he forgot the golden rule of software development: A software must work.
  • Another candidate sent me a package with tons of files. After I read the codes, I found that the codes were copied from other projects with very minor modifications. This kind of candidates should be avoided because cleaning up the code is a basic responsibility of a programmer.
  • A candidate has spent a lot of efforts on defining the variables (More than 20 variables were defined in the configuration sections), but he only put one line of comment (and no code implementations) inside the validation function, i.e.,
    //Validation goes here...

    He would impress me if he included at least one validation example.

  • One of the submitted answers is even more interesting (and ridiculous). It was created via some PHP-MySQL wizard websites. Although the result works fine (of course!), he does not receive any credit because his programming skills could not be proven.

So far, the best answer scores 60%. I don’t think this is an exciting result. If you found this useful, please let me know, thanks!

–Derrick

Our sponsors: