Solution: dd too slow on Mac OS X

When I was cloning SD cards on Mac OS X using dd', it takes ages to get things done. I was using the following command:

It takes much less time when using /dev/rdisk2 instead of /dev/disk2:

The reason is that rdisks are "raw" thus resulting in a higher R/W speed, according to man hdiutil` [1]:

/dev/rdisk nodes are character-special devices, but are “raw” in the BSD sense and force block-aligned I/O. They are closer to the physical disk than the buffer cache. /dev/disk nodes, on the other hand, are buffered block-special devices and are used primarily by the kernel’s filesystem code.


A “normal” sed on Mac

The sed program on Mac is not a standard (GNU) one. To get the normal one, use brew:

After this, alter PATH. For example, add the following line to your ~/.bash_profile:

And now you have a normal sed!


OpenVPN client TLS-Auth problem on Windows

It seems that the OpenVPN Client on windows does not support TLS-Auth with a separate key file. So instead, you can paste your key contents in your openvpn client’s config file and use some thing like the following (inline ta.key):

When not using the above but using something like:

The server log shows something like:

GitHub couples

I’m feeling good today because of theses things:

  1. My mobile phone ran out of battery and the alarm clock didn’t ring this morning, but I still managed to get up just in time and caught the bus at the last minute — and arrived at the company at my usual time.
  2. My manager told me it looks positive to renew my contract and hopefully it will be one and half years. He also says he tries to get it done before the summer vacation, which makes my life a lot easier. Also he says it’s possible to save my holidays till winter. So I’ll be back in China for some time in winter this year.
  3. A very old lady managed to stop and got on the bus even though she waved her hand a bit late to the bus driver. The bus driver was polite and that what I like about Finland: people generally don’t get angry.
  4. Here’s one very funny and geeky picture I saw from xda-developers. In case the link gets invalidated later, the picture reads: “So, where did you two meet?” “Windows users: at the office” “Mac users: at Starbucks” “Linux users: GitHub”.


Downgrade Preview in OS X Lion

I’ve had enough with the slow Preview application in Lion. After some digging I found this tutorial to downgrade the Preview in Lion to the Snow Leopard version. Basically you need to have a copy of both the and /System/Library/PrivateFrameworks/MeshKit.framework from Snow Leopard. If you need to associate the default app to open pdf/png with the downgraded Preview, you have to delete the original

Update: after installing OS X updates you need to remove the again and put the SL to /Applications/ directory.

i386-jos-elf toolchain on OS X Lion

Yesterday friend and I decided to follow the MIT Operating System Engineering course together in order to get a deep understanding of OS’s. And today I started setting up the cross compling environment for the labs. At first I wanted to get the toolchain from macports, but unluckily it didn’t successfully build binutils on my Mac. As a result, I started building the toolchain from the source code, following the instructions at

The programs you need for the toolchain include binutils, gcc, and gdb. For compiling gcc you also need GMP, MPFR, and MPC. The source codes are available at:

Unzip them in a directory and build binutils, gcc, and gdb one by one.

In order to build gcc, GMP, MPFR and MPC needs to be built first.

Note that it’s essential to build gcc in a directory different from the source code directory to avoid compiling errors.

Then make gdb:

QEMU is available in macports: