2011-04-09, Sat

Problems while installing language-javascript and yesod

While trying to install yesod using the haskell cabal package manager, I encountered these errors.

   cabal: happy is required but it could not be found
   language-javascript-0.4.4 failed during the configuration step.
   The Exception was: ExitFailure 1

What was missing was an entry in my PATH variable to point to ~/.cabal/bin. To fix the problem, I added the following two lines to my ~/.bash_profile script

   export PATH

Save, and try again.

   $ cabal install yesod
Isaac Su

tags: cabal happy haskell install language-javascript yesod

Comment [1]


2011-01-28, Fri

join XVID AVI video files using the linux command line

So I had two AVI files that were curiously split into CD1 and CD2 folders in transit, and I wanted to watch them as a single file rather than switching between files halfway through the feature.

Here’s how you can do it using a nifty program called mencoder

      mencoder -oac copy -ovc copy -noodml -o ./joined.avi 
               path-to/file1.avi path-to/file2.avi

(all on a single line)

  • -oac copy transfer mode for audio
  • -ovc copy transfer mode for video
  • -noodml don’t write OpenDML index
  • -o ./joined.avi output file
  • path-to/file1.avi path-to/file2.avi files you want to join in that order.

To be able to use mencoder you’ll need to install it by typing this into a terminal.

On Debian/Ubuntu

      sudo aptitude install mencoder

On Redhat/Fedora

      sudo yum install mencoder
Isaac Su

tags: avi bash linux mencoder mpeg3 xvid



2011-01-08, Sat

Write or pipe a disk image directly from tar.gz using tar and dd

The other night I was wanting to dd a fresh copy of the ChromeOS image onto an SD card on my eeePC 701.

Problem was, There was only ~700mb of free space on the eeePC’s puny 4GB SSD drive, so there was no way I could fully extract the 1.6gb image before writing it out.

So here’s how you can dd a image file directly from within a tar.gz archive.

      tar xzOf ChromeOS-Flow.tar.gz | dd of=/dev/sdb bs=1M

Allow me to take you through the parameters for tar one at a time.

  • x extract
  • z pass it through the gzip filter (i.e. decompress it)
  • O send the output through to stdout
  • f parameter for the file we’re working with (as opposed to a stream)

The magic is in the O character which allows you to “|” pipe the output from tar directly to dd which then writes the stream straight to the block device (in this case /dev/sdb).

Isaac Su

tags: bash dd gzip linux stdout tar unix

Comment [4]


2010-11-26, Fri

phpMyAdmin delay when loading database list

The phpMyAdmin on my local dev machine would take around 5-10 seconds to load up the list of databases in the left frame.

The puzzling thing was that the delay would only come up after a relatively long period of inactivity on the part of the database server which means it’s probably some sort of a caching issue.

Upon consulting the Status tab, the Created_tmp_disk_tables variable was coming up red. The advice given was “you may want to increase the tmp_table_size value”.

It so happens, that was exactly what was needed to be fixed.

  1. Open up the my.ini file in a text editor.
  2. Look for the tmp_table_size variable.
    tmp_table_size=38M // This was mine
  3. Change it to something larger like
  4. Restart your MySQL service.
  5. Enjoy the instant speed bump!
Isaac Su

tags: database delay list mysql phpmyadmin speed



2010-05-20, Thu

How to convert a Public network to a Home or Work network in Windows 7

I’ve been working with VirtualBox’s Host-Only Network interface and noticed that Windows 7 automatically places the Host-Only Network interface under the “Public Network” category with no way to change it. Now this is annoying because each time I need to access my Virtual Machine, I’ll need to drop Windows Firewall on Public Network. Here’s how I fixed it.

It turns out, as a security measure, Windows 7 treats any network interface that doesn’t have a gateway set as an “Unidentified Network”. Consequently, all “Unidentified Networks” are placed in the Public Network. Here’s what you need to do to fix it.

  1. Open up the Network and Sharing Centre.
  2. Click on the network interface that you would like to convert to Home/Work. This should bring up the Status window for the said interface.
  3. Click the Details button. Note that there isn’t a value for IPv4 Default Gateway, though, in my case there is an IP Address for the IPv4 DHCP Server. Mine says – note that because it will be a safe dummy IP address to use.
  4. Close the Network Connection Details dialog box.
  5. Back on the network interface status window, click on Properties to bring up the Network Properties window.
  6. Select Internet Protocol Version 4 (TCP/IPv4) and click *Properties.
  7. Click on Advanced….
  8. Under Default gateways, click Add and enter a dummy Gateway IP Address (I used for mine).
  9. Add, OK, OK, OK and Close.
  10. A window should pop-up asking what category you would like to place the network interface under.
  11. Congratulations!
Isaac Su

tags: adapter firewall gateway home interface networking public unidentified windows-7 work

Comment [2]


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