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Tag: OS

Solution: dd too slow on Mac OS X

Published 2013/10/09 by Daoyuan Li

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:

diskutil unmountDisk /dev/disk2
sudo dd bs=1m if=~/Downloads/2013-10-09.alice.img of=/dev/disk2

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

diskutil unmountDisk /dev/disk2
sudo dd bs=1m if=~/Downloads/2013-10-09.alice.img of=/dev/rdisk2

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.

[1] http://superuser.com/questions/631592/mac-osx-why-is-dev-rdisk-20-times-faster-than-dev-disk

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A “normal” sed on Mac

Published 2013/07/08 by Daoyuan Li

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

brew install gnu-sed

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

PATH="/usr/local/opt/gnu-sed/libexec/gnubin:$PATH"

And now you have a normal sed!

 

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OpenVPN client TLS-Auth problem on Windows

Published 2013/04/18 by Daoyuan Li

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):

client
dev tun
proto udp

# enter the server's hostname
# or IP address here, and port number
remote server_ip port_number

resolv-retry infinite
nobind
persist-key
persist-tun

# Use the full filepaths to your
# certificates and keys
ca "C:\\yabroad.tblk\\ca.crt"
cert "C:\\yabroad.tblk\\client.crt"
key "C:\\yabroad.tblk\\client.key"

key-direction 1

<tls-auth>
#
# 2048 bit OpenVPN static key
#
-----BEGIN OpenVPN Static key V1-----
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
-----END OpenVPN Static key V1-----
</tls-auth>


ns-cert-type server
comp-lzo
verb 1

When not using the above but using something like:

tls-auth ta.key 1  # which works for tunnelblick

The server log shows something like:

Thu Apr 18 20:55:26 2013 TLS Error: incoming packet authentication failed from [AF_INET] IP_ADDRESS:60454
Thu Apr 18 20:55:57 2013 Authenticate/Decrypt packet error: packet HMAC authentication failed
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Downgrade Preview in OS X Lion

Published 2012/04/23 by Daoyuan Li

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 Preview.app 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 Preview.app.

tar -pczf Preview.app.tar.gz /Applications/Preview.app
sudo rm -rf /Applications/Preview.app

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

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i386-jos-elf toolchain on OS X Lion

Published 2012/03/18 by Daoyuan Li

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 http://pdos.csail.mit.edu/6.828/2011/tools.html.

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:

wget http://ftpmirror.gnu.org/binutils/binutils-2.21.1.tar.bz2
wget ftp://ftp.gmplib.org/pub/gmp-5.0.4/gmp-5.0.4.tar.bz2
wget http://www.mpfr.org/mpfr-current/mpfr-3.1.0.tar.bz2
wget http://www.multiprecision.org/mpc/download/mpc-0.8.2.tar.gz
wget http://ftpmirror.gnu.org/gcc/gcc-4.5.1/gcc-core-4.5.1.tar.bz2
wget http://ftpmirror.gnu.org/gdb/gdb-6.8a.tar.gz

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

$ tar jxvf binutils-2.21.1.tar.bz2
$ cd binutils-2.21.1
$ ./configure --target=i386-jos-elf --disable-nls && make && sudo make install

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

$ mkdir -p libs/install
$ mv gmp-5.0.4.tar.bz2 mpfr-3.1.0.tar.bz2 mpc-0.8.2.tar.gz libs/
$ tar jxvf gmp-5.0.4.tar.bz2
$ mkdir gmp-build; cd gmp-build
$ ../gmp-5.0.4/configure --prefix=$(cd ../install && pwd)
$ make && sudo make install
$ cd ..
$ tar jxvf mpfr-3.1.0.tar.bz2
$ mkdir mpfr-build; cd mpfr-build
$ ../mpfr-3.1.0/configure --prefix=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-gmp=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/
$ make && sudo make install
$ cd ..
$ tar zxvf mpc-0.8.2.tar.gz
$ mkdir mpc-build; cd mpc-build
$ ./configure --prefix=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-gmp=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-mpfr=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/
$ make ; sudo make install
$ cd ..
$ tar jxvf gcc-core-4.5.1.tar.bz2
$ mkdir gcc-build; cd gcc-build
$ ../gcc-4.5.1/configure --target=i386-jos-elf --disable-nls --without-headers --with-newlib --disable-threads --disable-shared --disable-libmudflap --disable-libssp --with-gmp=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-mpfr=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/ --with-mpc=/Users/daoyuanli/Downloads/i386-elf-gcc/libs/install/
$ make ; sudo make install

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

Then make gdb:

$ tar zxvf gdb-6.8a.tar.gz
$ mkdir gdb-build; cd gdb-build
$ ../gdb-6.8/./configure --target=i386-jos-elf --program-prefix=i386-jos-elf- --disable-werror
$ make && sudo make install

QEMU is available in macports:

$ sudo port install qemu
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