Tech Tots

Logging request parameters in CodeIgniter

2011-12-16T14:34:00.001+08:00

The application I'm currently working on provides services to mobile devices. As such, I need to constantly check what values the mobile devices are POST-ing to the application. Instead of adding a call to all functions in the controllers to perform this task, I decided to implement a hook in the application. Hooks are supported in CodeIgniter (more info here). Here's my hook class to perform

Copying a running VM to external host

2011-12-16T14:10:00.001+08:00

Friend had a small incident the other day where KVM/QEMU seg-faulted and lost communication with a running VM. The VM was still running but it isn't writing to persistent storage. We decided to do a live backup of the running VM. Although this is definitely NOT recommended, we were left with no other choice as shutting down the VM would mean losing all changes made. The VM is running Linux

Using mysqldump to export CSV file

2011-12-15T22:17:00.000+08:00

By default, mysqldump outputs SQL table dumps. If you ever need to export a table (or even a database) in CSV format using only mysqldump, here's the quick and easy way without using any additional clients: mysqldump -u root -p --fields-terminated-by="," --fields-enclosed-by="" --fields-escaped-by="" --no-create-db --no-create-info --tab="." information_schema CHARACTER_SETS mysqldump will

Using logback to log to a syslog server

2011-12-12T16:44:00.001+08:00

In my previous posts, we've configured a rsyslogd server to accept remote connections via TCP/UDP as well as a rsyslogd instance to write to a remote rsyslogd server. We'll now take this further by logging to the rsyslogd server we've configured earlier using the logback library (http://logback.qos.ch/). Besides the logback JAR files, you'll need to grab the latest SLF4J libraries as well

rsyslog: Logging to remote server

2011-12-12T15:20:00.001+08:00

Now that we've setup the rsyslogd server to accept incoming connections (NOTE: UDP somehow didn't work. I had to configure rsyslogd to listen to TCP instead); we can now configure the "client" rsyslogd instance to log to a remote server. In the "client" server, we'll need to edit the same configuration file /etc/rsyslog.conf. I've added the highlighted lines below: [...] ############### ####

rsyslog: Enabling remote logging service in Ubuntu

2011-12-12T11:47:00.001+08:00

Newer versions of Ubuntu (since 9.10 according to rsyslog wiki: http://wiki.rsyslog.com/index.php/Ubuntu) comes with rsyslog instead of sysklogd. Was trying to enable it via the sysklogd way by adding the "-r" option in the startup script. That obviously didn't work :) What you'll need to do is just uncomment 2 lines in the /etc/rsyslog.conf file: # provides UDP syslog reception $ModLoad

CSS3 Generator

2011-12-08T22:33:00.001+08:00

I'm currently implementing (or rather trying to implement :P) a site with HTML5 and CSS3. Found a very nifty site which helps in generating cross browser CSS3 effects e.g. shadows, border radius, etc: http://css3generator.com/ Give it a try and see if it helps you as much as it helped me :)

Barebones JSF2 Eclipse project

2011-12-08T09:09:00.000+08:00

Quick view on minimal libraries required to get a JSF2 project running in Eclipse (should work everywhere else): com.springsource.javax.servlet.jsp-2.1.0.jar ==> Obtained from Spring framework dependencies package com.springsource.javax.servlet.jsp.jstl-1.1.2.jar ==> Obtained from Spring framework dependencies package javax.faces.jar ==> Obtained from http://javaserverfaces.java.net/.

Setting up Hadoop in clustered mode in Ubuntu

2011-12-08T08:53:00.000+08:00

Overview This entry details the steps I took to setup Hadoop in a clustered setup in Ubuntu 11.10. Hadoop version 0.20.205.0 was used to setup the environment. The Hadoop cluster consists of 3 servers/nodes: node616 ==> namenode, tasktracker, datanode, jobtracker, secondarynamenode node617 ==> datanode, jobtracker node618 ==> datanode, jobtracker In an actual production setup, thet namenode

Connecting to remote MySQL via SSH in Ubuntu

2011-12-06T23:29:00.000+08:00

I had to access my MySQL server via SSH tunnel on my Ubuntu desktop machine. First up, setup ssh to tunnel the server's MySQL port (default 3306) to my Ubuntu's desktop machine port 13306: ssh mylogin@myserver.com -p 4265 -L 13306:127.0.0.1:3306 However, when I tried accessing port 13306 on my Ubuntu desktop, it failed: $ mysql -u root -p -P 13306Enter password:ERROR 1045 (28000): Access

Commercial Use Free Fonts

2011-11-04T14:34:00.000+08:00

Stumbled upon an awesome website offering commercial use free fonts: http://www.fontsquirrel.com/ It also provides @font-face kits (CSS3) where you can upload a font file and it'll generate the necessary files for you to use in your CSS3 styles. Awesome!!!!

Installing Open Nebula 3.0 on Ubuntu 10.04

2011-10-06T22:03:00.000+08:00

Downloaded the .deb file from Open Nebula website (http://dev.opennebula.org/packages/opennebula-3.0.0/Ubuntu-10.04/opennebula_3.0.0-1_amd64.deb) Installed it but gave some problems hence had to do the following steps: dpkg -i opennebula_3.0.0-1_amd64.debapt-get install libmysqlclient16 libxmlrpc-c3apt-get -f install Once that's installed, the oned daemon will be started automatically.

EHCache with Spring AOP

2010-02-20T13:50:00.000+08:00

Building on the previous post (Spring AOP with @AspectJ annotations), we now add EHCache functionality to the Aspect class. We won't be adding any new Java class files, but we'll be modifying the existing class files. Here's a screenshot of the finished project in Eclipse. New elements are highlighted in red. Adding EHCache functionality Add the EHCache JAR file to the project. We'll

Spring AOP with @AspectJ annotations

2010-02-19T09:12:00.001+08:00

Here's a quick sample on how to use Spring's AOP feature with @AspectJ annotations. First off, please read the Spring Reference manual on AOP. This post is a copy and paste tutorial (hopefully I get it right :P). We begin by creating a normal Java Project in Eclipse. I've named it "springtest". You can name it whatever you like. Here's a screenshot of the project in Eclipse: Take note of

Load balancing OpenVPN connections via IPVS (Linux Virtual Server)

2010-01-21T11:57:00.000+08:00

First Steps First off, I've performed the setup and configuration on my own local PC using VirtualBox VMs. Network for all the VMs are set to bridge mode. Here's how the servers are configured: director--------Fedora 12VIP=eth0:0 192.168.1.150RIP=eth0 192.168.1.200ovpnserver1-----------UbuntuRIP=eth0 192.168.1.201VIP=lo:0 192.168.1.150 (no arp)ovpnserver2-----------UbuntuRIP=eth0

Mounting an NTFS partition in a folder

2010-01-19T12:13:00.000+08:00

To mount an NTFS partition in a folder similar to what's done in Unix systems, do the following: Go to the "Run..." screen and type in compmgmt.msc. Click on "Disk Management". Right click on the volume you want to use and select "Change Drive Letter and Paths..." Click "Add". Another window will be displayed like below: Click on the second radio box "Mount in the following empty NTFS

Connecting to MQ using Spring without WAS

2010-01-14T16:10:00.002+08:00

Here's how to connect to MQ using spring without WAS. First, here's the properties value for the connection settings: # MQ related values mq.jms.qcf=IBMMQQCF mq.jms.request.queue=TEST.REQUEST.QUEUE # Connection details mq.host.url=192.168.1.200:1415/SYSTEM.DEF.SVRCONN mq.factoryclass=com.ibm.mq.jms.context.WMQInitialContextFactory # Authentication details mq.auth=simple

Installing Shorewall in Ubuntu

2010-01-14T10:31:00.001+08:00

I started off with the simple command: # apt-get install shorewall shorewall-doc Thought everything was installed properly. But I got the following error instead: # shorewall start Compiling... No shorewall compiler installed Seems I'm missing one more package: # apt-get install shorewall-perl Once the shorewall-perl package is you should get the following output: #

Configuring OpenVPN + FreeRADIUS + MySQL

2010-01-11T15:35:00.002+08:00

Here's a quick guide on how to configure OpenVPN to use FreeRADIUS for authentication. I've only tried it on Ubuntu Karmic. YMMV on other distros. Download the radiusplugin here http://www.nongnu.org/radiusplugin/. You'll have to compile it from source as there's currently no deb package for it. Compile steps below: # apt-get install libgcrypt11 libgcrypt11-dev build-essential # make The

Installing and configuring daloRADIUS

2010-01-11T03:22:00.002+08:00

With FreeRADIUS+MySQL installed, it's now turn to install daloRADIUS; a web-based management system for FreeRADIUS. Before installation, ensure that Apache, PHP and MySQL have been installed and running. You'll need PHP PEAR as well. Use the following command to install the required libs: # apt-get install php-pear # pear install DB Get the latest version of daloRADIUS from http://

Installing and configuring FreeRADIUS with MySQL authentication

2010-01-10T13:13:00.003+08:00

Here's a *near* step-by-step guide to setup FreeRADIUS with MySQL backed authentication done on Ubuntu 9.10 (Karmic). Start by installing the necessary deb files: # apt-get install freeradius freeradius-mysql Add the following lines to the /etc/freeradius/users file: abc Cleartext-Password := "123" Stop freeradius service just in case: /etc/init.d/freeradius stop Now test using the

Creating split RAR files via command line

2010-01-08T17:43:00.002+08:00

Command below creates split RAR files (e.g. file.part001.rar, file.part002.rar...) via the command line: $ rar a -m0 -v50000k

That creates files of 50,000k a piece without any compression (-m0). The most important option here is the -v option :)

Creating network aliases for single network interface

2010-01-08T17:31:00.000+08:00

First some assumptions: network interface is aliased to eth0 eth0 assigned to 192.168.1.1 Here's how you assign more than one IP to a single network interface in Ubuntu/Debian: # ifconfig eth0:0 192.168.1.2 up That's it. Wait for a while for the interface to become active and you'll be able to configure services to serve from that IP. To make the change permanent, edit the /etc/network/

.NET and Apache Axis Interop Problem

2010-01-08T16:56:00.004+08:00

I've been using Apache Axis for a long time to publish web services in Java apps. But recently, it's the first time that a .NET client is used to call the web services published via Axis. Although I do not have the exact error messages in the .NET client, the client mentioned they received "null" errors when parsing the response. First thing to do was to disable "multirefs" output. This can

Removing invalid/encoded characters from filenames

2010-01-06T16:09:00.001+08:00

If you see the following output in your file system: drwxrwxrwx 2 www-data www-data 4096 Jan 5 03:30 ?????? - ?Q?U?H-?X?Y??Like?t??? drwxrwxrwx 2 www-data www-data 4096 Jan 5 03:41 ???O?? ?@?????j?t??? It'll be difficult to work with the files. By using "detox", you can remove all invalid characters from the files/folders. In Ubuntu, simply perform the following command to install it:

List of installed packages in Ubuntu/Debian

2010-01-06T11:40:00.000+08:00

Use the following command to show the list of installed packages in Ubuntu/Debian: # dpkg --get-selections acl install acpi-support install acpid install adduser install aisleriot install [..] You can then use grep to look for the packages you want.

Grep in Windows

2010-01-06T09:47:00.001+08:00

Ever wanted to grep a string in Windows console? Here's how: c:\>netstat -an | findstr 50000 There are other options for findstr. You can check it out by typing "help findstr".

(L)AMP installation on Ubuntu

2010-01-05T20:29:00.001+08:00

Just got a new server up and running. Here are the commands to install Apache2, PHP5 and MySQL: # apt-get install apache2 libapache2-mod-php5 mysql-server-5.1 php5-mysql php5-mcrypt Make sure you do a restart. Sometimes the apt-get process doesn't restart Apache properly to ensure the PHP5 module is loaded. # /etc/init.d/apache2 restart

Compiling and installing libtorrent/rtorrent

2010-01-05T17:35:00.001+08:00

Here are the steps to compile and install libtorrent/rtorrent. The latest stable version of libtorrent/rtorrent is 0.12.6 and 0.8.6 respectively as of writing this article. The tarballs can be obtained here. Following commands must be run as root. # apt-get install build-essential libssl-dev libssl0.9.8 libsigc++-2.0-dev libncurses5-dev libncursesw5-dev libcurl4-openssl-dev libssl-dev

OpenVPN with pam_mysql username/password authentication

2010-01-03T18:27:00.002+08:00

Here's how I setup OpenVPN with pam_mysql using only username/password authentication (insecure, but really easy on the admin side :P). Target platform is Ubuntu Jaunty. For starters, you'll need the following installed: openvpn mysql - server installed and running Get the latest version of pam_mysql from http://pam-mysql.sourceforge.net/. Untar it into a working directory. The latest

Compiling openvpn-auth-ldap on Debian

2010-01-03T07:32:00.000+08:00

Here are the steps I followed to compile openvpn-auth-ldap plugin on Debian: apt-get install re2c apt-get install libldap2-dev apt-get install gobjc ./configure --prefix=/usr/local --with-openldap=/usr/include --with-openvpn=/usr/include/openvpn The libldap2-dev package is required for openldap header files while the gobjc package is required to satisfy sanity check on cpp. Openvpn's header

Opera Mini 5 Beta 2

2009-12-11T02:47:00.000+08:00

The new version of Opera Mini 5 Beta is out. It's no longer called Opera Mini but Opera Mobile. Either way, it's shaping up to be a really nice browser. Gone are the days of it being a J2ME app. It's now a native S60 application. Speed increase is very noticeable. Give it a go here: http://www.opera.com/mini/next/

Using 'ps' to find CPU intensive processes

2009-11-19T09:59:00.001+08:00

If you've been using 'top' to determine which processes use the most CPU resource, there's another way. Use 'ps' and sort the output via CPU. Here's the command: ps aux --sort -cp

Using whois To Search For Records

2009-10-15T16:45:00.000+08:00

Here's a nice tip to search for relevant records from a DNS using whois: whois -h "whois.apnic.net" -a "Google" This will search "whois.apnic.net" for all records matching "Google". Good stuff :)

Installing Virtualbox Guest Additions in Centos 5

2009-10-11T01:58:00.000+08:00

To install VBox's Guest Additions in CentOS 5, simply run the following commands:yum install gcc -yyum install kernel sources -yyum install kernel-devel -yReboot the system. Right after that, run the VBox additions .sh file.

XML Pretty Formatting

2009-10-09T16:14:00.000+08:00

I've had this problem for a long time. A huge XML document which is not formatted. Finally found the simplest solution... HTML Tidy library. Grab the EXE from SourceForge: http://tidy.sourceforge.net/. Then run the following command:tidy -xml -indent -quiet -o "output.xml" input.xmlThis will read the input.xml file and treat it as a well formed XML. No additional output will be displayed on

Extracting audio stream from an AVI file using mencoder

2008-07-22T23:00:00.000+08:00

If you ever need to extract the audio stream from an XVID/MP3 encoded file and save the audio stream back into MP3 format, here's the command to do it using mencoder:mencoder "${file}" -of rawaudio -oac mp3lame -ovc copy -o audio/"${file/%avi/mp3}"This commands saves the output in the audio directory. The portion ${file/%avi/mp3} uses bash string replacement to replace the avi to mp3 within the

MySQL: "Cannot insert new word" error

2008-07-22T11:36:00.000+08:00

The internal forum (powered by phpBB) I was using was suddenly giving me the error "cannot insert new word". Tailing /var/log/messages and MySQL error logs came up empty. After Googling a bit, it seems that the MySQL tables are corrupt. Running the SQL command below fixes the problem beautifully:repair table [tablename];

Kernel panic in Linux 2.6.26 on VirtualBox

2008-07-21T13:23:00.000+08:00

I've been trying to get Intrepid Ibex Alpha 1 & 2 to boot on VirtualBox in a Linux host; but due to what it seems like a kernel bug, I've been unable to do so. If you're interested to see the development/status of this bug, click here.

HTML Cache Headers

2008-07-21T11:26:00.000+08:00

I've always get burnt for setting the wrong HTTP headers for cache control. So here's the braindump of what these headers are and what to set them to. The RFC for HTTP header field definitions is located here. Note that it's always better to set the headers both in the HTTP-EQUIV META tags as well as to set it via the headers as some browsers have problems parsing the HTTP-EQUIV META tags.There

Cache Control Settings

2008-07-21T00:55:00.000+08:00

I've always get burnt for setting the wrong HTTP headers for cache control. So here's the braindump of what these headers are and what to set them to. The RFC for HTTP header field definitions is located here.Note that it's always better to set the headers both in the HTTP-EQUIV META tags as well as to set it via the headers as some browsers have problems parsing the HTTP-EQUIV META tags.There

Restarting NetworkManager in (K)ubuntu

2008-07-20T21:55:00.000+08:00

If NetworkManager's acting up on your (K)ubuntu installation, you can restart 2 daemons instead of performing a reboot. Here's what you do:sudo /etc/dbus-1/event.d/25NetworkManager restartsudo /etc/dbus-1/event.d/26NetworkManagerDispatcher restartOnce that's done, wait for a while for the daemon to refresh itself. Then try to re-associate your machine with an AP.

Backup fun with netcat (nc)

2008-07-03T23:26:00.000+08:00

Was asked to help on backing up files in one server and then transfer the image to another server. Sounds simple, but unfortunately the server which files are to be backed up has very limited disk space and prevents me from creating a tar-ball. Instead of creating a tar-ball in the server, I used netcat (or known as nc) to stream the files over to another server while running the tar command. On

Configuring Huawei E220 USB GSM modem on Kubuntu Hardy

2008-07-03T23:11:00.000+08:00

Managed to get my hands on a repackaged Huawei E220 USB GSM modem provided by Maxis via their Maxis Broadband package. Since there's no instructions to install and use it on Linux (Windows and OSX instructions are provided), I decided to see how Linux will behave when it's plugged into the USB port.Lo and behold; my system's /var/log/messages when it's plugged in:Jul 3 10:56:50 mymachine kernel

Installing/Configuring kismet on Ubuntu

2008-07-01T11:46:00.000+08:00

Been experimenting with kismet over the weekend and was finally well enough to configure it after some quick digging.InstallationDo a simple apt-get to install kismet:apt-get install kismetThat's all there to it. Please note that the version in Ubuntu's repo is 2007-10-R1-2build1. It's a lot older than the one currenly available for download i.e. Kismet-2008-05-R1.ConfigurationIf you run kismet

Intrepid Ibex Alpha 1

2008-06-29T22:43:00.000+08:00

The first alpha of the next Ubuntu version code named "Intrepid Ibex" is now available! Get the release info and the release notes here. Gonna download it and try it out on a VM. Let's see what's new in a few :)I'm downloading Kubuntu 8.10a1 as I type this. However, seems like only the "alternate" version is available. Strange...

Argument list too long

2008-06-26T14:08:00.000+08:00

Ever tried to do a "rm *" on a directory and got the error "argument list too long"? Use xargs and chain the commands!ls | xargs rmFound this gem here: http://www.shell-fu.org/lister.php?id=251

UPDATE...FROM

2008-06-26T09:37:00.000+08:00

The UPDATE...FROM SQL statement saved me tonnes of time during a previous system migration. Using the FROM clause in an UPDATE statement allows you to pull data from one or more tables into the data you're updating.Say you have a table with 10,000 user records (let's call it tbl_migration_1) which you'd like to find the last login time which is stored in the master user table (let's call it

Using CURL to obtain superflous HTTP verbs

2008-06-25T11:56:00.000+08:00

Instead of using netcat or telnet to check a website for allowing superflous HTTP verbs, CURL makes it simpler:curl -X OPTIONS -I An example of the output is shown below:# curl -X OPTIONS -I http://thestar.com.myHTTP/1.1 200 OKAllow: OPTIONS, TRACE, GET, HEADContent-Length: 0Server: Microsoft-IIS/6.0Public: OPTIONS, TRACE, GET, HEAD, POSTX-Powered-By: ASP.NETDate: Wed, 25 Jun 2008 03: