Tech Blog

It was all relatively painless and it's quite amazing how far Wine has come.

Installing Lego Digital Designer

Go to the Lego Digital Designer site and download the Windows version.

I got LDD 3.1.3 which was the latest version available at the time.

Now - to make it all work you need to install Wine and I used the latest version from the wine PPA team.

Add the wine ppa:

You'll then see:

Now to update the list of available software:

And then install wine and winetricks

Wine lets you run Windows software on other operating systems, in this case Ubuntu.

Wine tricks provides a simple way to install native versions of some of the libraries that are not 100% compatible - by looking at the Wine App DB I discovered that it had problems with missing font's (Tahoma) and scrolling which was fixed by installing Quartz.

Then install double click on the install file for LDD and it should be up an running in no time.

If you get a warning about it not being Executable you may need to right click on the application and select Properties - and then from the Permissions tab select "Allow executing file as program"

Son is now very happy with Lego Digital Designer :-)

The find utility has an option to find a file newer than another file. By creating and empty file with a specific creation date we can do the search:

To show all files newer than 2010-01-01 use:

Or to create a tar archive of them use xargs like so:

Easy. Mark

These are:

• Logging to DB instead of log files
• Runtime configuration of logging.

Logging to DB instead of log files

Coming from a web development background rather than a sysadmin background I'm far more comfortable manipulating and analysing data using SQL. So to be able to log all the queries or just the slow queries for an application to the db during application development or load testing is a huge benefit.

To enable logging to DB you can add the following to your my.cnf

The logs will be written to the 'slow_log' and 'general_log' tables in the mysql database.

Note - logging to tables has more overhead than logging to file, so would suggest using it primarily for development purposes.

Full details of the options are on the mysql manual on log tables

Runtime configuration of logging.

This allows you to turn on and off logging without restarting MySQL - which just saves a little bit of time and makes it much nicer for debugging problems.

To turn on the logging of all queries run:

And to turn them both off use:

If you also want to see queries not using indexes in the slow query log you can set the following variable:

Hope it helps, Mark

To do this I used a SSH sock proxy like I have previously blogged about.

So I fired this up so that I could review the site I wanted to look at. It worked a charm through firefox but there is no where to set up the proxy in jmeter.

To make it work you need to let the JVM know what proxy to use like so:

No jmeter will use the socks proxy on port 8080 on my local machine. Nice.

About Learnosity

Our service:

• Makes it practical for students to practice Oral and Aural skills
• Is efficient and effective for teachers, as they can listen to each student individually at a time to suit them
• Can be used for homework assignments or “High Stakes Assessments”

We are continuing to grow our core development team and we need another great developer to help us keep up with demand.

We need someone who can:

• Use Javascript or Actionscript to create great user interfaces
• Develop highly scalable web applications
• Cut code with the best in the world

You will also need to be:

• energetic with a butt kicking attitude
• ready to create cutting edge web 2.0 apps
• keen to continue learning new technologies
• able to have a conversation with non technical people

You'll need:

• 3 or more years of programming experience
• Expert in at least on Client side language (Actionscript or AJAX)
• Expert in at least one Server side language (eg PHP, Java, ColdFusion, etc)
• Understanding of Object Oriented design
• Understanding of XHTML and CSS

It would be good if you have:

• A degree in Computer Science, Engineering or similar.
• been working with open source tools
• been playing around with iPhone/Android applications
• experience with some of Linux/VOIP/SIP/Asterisk/Jabber/XMPP

This is a full time role and you will be working in a casual workplace with flexible hours in the Sydney CBD.

If this sounds like the job for you, email a covering letter explaining why you'll be great and your resume to mark@learnosity.com - no agencies please.

Seem to be on a roll with Sox tonight. Also figured out how to normalise audio files nicely.

The first thing to do with sox is to get it to calculate the max volume adjustment possible:

This will return a number like: 4.234

You can then call sox again using this number:

And if you're feeling particularly good you can put the whole command on a single line as follows:

Easy when you know how.

However, this time I finally managed to get past all the hurdles and jump through all the hoops to make this work.

Scenario is a follows. Audio file is comes in in alaw or ulaw format and we want to trim any silence before and after it.

First step is to convert it from alaw to pcm encoded wav file as SOX has issues filtering silence in alaw files

Then we do the trimming in one fell swoop.

A huge thanks to this article for giving such a thorough overview of the how silence detection works in sox.

Too easy, when you know how :-)

This sets turns it on for everything except gif,jpeg,png or mp3, as these are already well compressed.

Cheers, Mark

In order to come up with a reliable solution to this we decided to use the SSH server we had available and tunnel the windows sharing across the local port forwards, much simpler and more reliable.

Thanks to this article it was a breeze to set up.

Steps are as follows:

• Create loopback adapter on windows
• Configure loopback adapter on windows
• Reboot
• Configure SSH connection
• Test it all out

Create loopback adapter on windows

We'll give your computer an additional (fake) IP address, and we'll port forward to that address instead of the computer's real IP. Windows XP will continue to do file sharing on the real IP address. We'll assign it an IP of 10.0.0.1 (that's what we configured putty to use above.)

1. System->Control Panel->Add Hardware
2. Yes, Hardware is already connected
3. Add a new hardware device (at bottom of list)
4. Install the hardware that I manually select
5. Network adapters
6. Microsoft , Microsoft Loopback Adapter
7. (Go through the installation procedure.)

Configure loopback adapter on windows

1. Open your new fake ethernet adapter (Network Connections) , enter a made-up IP address (I suggest 10.0.0.1, which is a privately routable address that most folk don't use.)
2. Enable Client for Microsoft Networks.
3. Disable File and Printer Sharing for Microsoft Networks
4. Enable Interent Protocol (TCP/IP)
5. Click on properties for TCP/IP.
6. Enter your chosen IP address (10.0.0.1), subnet mask (255.255.255.0). You can leave gateway blank.
7. Under advanced->WINS, Enable LMHosts Lookup and Disable NetBIOS over TCP/IP

Reboot

Configure SSH connection

• Download Putty
• Enter IP address
• Enter Auth Key (if using SSH keys)
• Enter Port forwards for: (these connect the ports on you local machine to
  • 10.0.0.1:137 to 127.0.0.1:137
  • 10.0.0.1:138 to 127.0.0.1:138
  • 10.0.0.1:139 to 127.0.0.1:139
  • 10.0.0.1:445 to 127.0.0.1:445
• Save the config.

Test it all out

• Open putty, load the settings and connect.
• Open Exporer and type in: \\10.0.0.1\

You should now be connected to your remote windows system over a secure encrypted tunnel.

Cheers, Mark

Running the command df was showing lots of free space.

However, a quick google on cp "no space left on device" turned up the suggestion to try:

This showed up the problem straight away - I had run out of inodes.

Once the problem is identified it is generally easy to resolve, so I figured out that there was a cron job that was running a wget task and not discarding the output, and so had saved 600,000+ files in their home directory.

However, when I tried to delete them I encountered another problem:

There were so many files that I couldn't use standard delete commands.

Another quick google turned up this gem:

I ran the following command to check that I was going to delete the correct files:

One final thing was to fix up the cron job that was causing the problem. Adding the parameter --delete-after to wget kept the directory nice and clean.

All fixed. One of the things this has reinforced for me is how important it is to have /home on a seperate partition. If this had not been the case then the problem would have taken longer to happen (due to larger filesystem) but would have been more destructive - as all systems and processes would not have been able to create new files.