GUO Jian's Technical Blog

Configure gtalk in pidgin

2010-11-28T20:03:00.000-08:00

Basic Tab
Protocol: xmpp
Username ; username_only (no need for @gmail)
Domain: gmail.com
Resource: Home
Password: Your_GMAIL_ Password

Advance tab
Force old (port 5223) SSL: Checked
Allow plaintext auth over unencrypted streams: Un-Checked
Connect Port: 443
Connect Server: talk.google.com
File Transfer For Proxies: Leave blank or proxy.jabber.org

Proxy type
Use Global Proxy Settings

create shared C library

2010-11-23T22:21:00.001-08:00

How to create and use your own shared C library using gcc? This can be done in 4 steps.

write your library code, say sum.c with header file sum.h, and save them in your library folder, say ~/local/lib for the source, and ~/local/include for the header file.
compile it using gcc

gcc -I ~/local/include -c sum.c

This will produce a object file sum.o
create a static library named "hash", do

ar rcs libhash.a sum.o

More than one *.o files can be included in single library
you are ready to use it by :
- include the "sum.h"
- compile it using gcc -I ~/local/include -L ~/local/lib -lhash ...
To save typing -I xxx and -L xxx every time to use the library, save the path for auto lookup by adding the following lines to ~/.bashrc or ~/.bash_profile:

# for header files
export C_INCLUDE_PATH=~/local/include:$C_INCLUDE_PATH
# for linking library
exprot LD_LIBRARY_PATH=~/local/lib:$LD_LIBRARY_PATH
export LIBRARY_PATH=~/local/lib:$LIBRARY_PATH

For more readings on differences of shared and static library, see here.

Timing in C

2010-11-18T21:50:00.000-08:00

#include <sys/time.h>
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>

typedef uint64_t u64;
static inline u64 T2L()
{
  struct timeval tv;
  gettimeofday(&tv, NULL);
  return 1000000ULL * tv.tv_sec + tv.tv_usec;
}

static u64 _t_start_;
u64 tstart()
{
  _t_start_ = T2L();
  return _t_start_;
}

u64 tdiff()
{
  return T2L() - _t_start_;
}

void ptdiff()
{
  u64 d = T2L() - _t_start_;
  printf("%lu sec %lu usec\n", d/1000000, d%1000000);
}

My Experience with Latex

2010-07-12T00:01:00.000-07:00

Most of the papers on Maths, especially those with mathematical formulas, are typeset with Latex. Here I list some of tips:

To include images with different formats:
- PDF, one can use pdflatex to compile
- ps, eps, use latex
Sometimes, when one has to latex (because of some other packages used), one can convert the formats of the images, using the command
convert
To draw and include pictures, as I mentioned in previous posts, I use JPicEdt for editing to pst files, and then include them by

\include{picture.pst}

However, when pst format is used for Latex, one has to use three steps to compile:

latex -> dvi2ps -> ps2pdf

in order to get the PDF file.

reinstalled ubuntu 9.10

2010-05-31T08:58:00.000-07:00

Here is what I do to customize it according to my working package:

sudo apt-get update
Chinese Support:
sudo apt-get install ibus ibus-qt4 ibus-pinyin
im-switch -s ibus
vim: my favorite editor and copy my customized .vimrc file
sudo apt-get install vim
To add me to sudoer list, and enable the nopasswd function to avoid keep keying in the password. see: /etc/sudoers
Customize my firefox:
- enable the add-on Xmarks, and greasemonkey for downloading google PDF documents
- sudo aptitude install ubuntu-restricted-extras (flashplayer)
- sudo apt-get install sun-java6-jre sun-java6-plugin sun-java6-fonts(jre)
IM - pidgin with integrated skype
- sudo apt-get install pidgin
- download http://www.skype.com/go/getskype-linux-beta-ubuntu-32
- http://eion.robbmob.com/skype4pidgin.deb
- sudo dpkg -i *.deb
workspace: kile, latex, etc
- sudo apt-get install kile jabref rapidsvn meld okular
- configure rapidsvn to use kile and meld
- download and install: http://downloads.sourceforge.net/jpicedt/jpicedt-install_1_4_1_03_20071021.jar?download
- add llncs.cls to /usr/share/texmf/tex/latex/guojian/; sudo texhash
Eclipse with C/C++
- sudo apt-get install eclipse
- Help >> Install New Software, select "Galileo Update Site - http://download.eclipse.org/releases/galileo/", and choose "Eclipse C/C++ Development Tools"
Lastly, copy my customized .bashrc, download from: here

That's all for today :-)

Install Chinese input method

2009-11-07T01:51:00.000-08:00

Recent ubuntu versions switch to use ibus as the system input. ibus supports chinese well also, so I switch from scim. To install

sudo apt-get install ibus ibus-qt4 ibus-pinyin
im-switch -s ibus

clone ubuntu to new disk

2009-10-24T02:40:00.000-07:00

source is from here.

"I always make this, booting from Ubuntu live cd and using dd to make a copy from older disk to newer disk

Assuming /dev/hda size is <>

Open a terminal and type:

sudo -i

fdisk -l

dd if=/dev/hda of=/dev/hdb

Replace /dev/hda with your Ubuntu Drive
Replace /dev/hdb with the drive you wish to copy TO!

check & double check the fdisk -l output

Unplug the older disk and keep it as secure backup of your current installation for a while and plug the new hard disk as primary and boot your pc.
After you can put your old disk as secondary on the same pc or use it on a different pc (it usually works, you might need to reconfigure graphics layer) .

Then booting from Ubuntu live cd and using System → Administration → Partition editor, increase the just copied partitition size to fill new disk size (bigger than previous disk).

This is my usual Ubuntu cloning method...

Hope this helps"

Write paper using Latex under ubuntu

2009-10-23T09:55:00.001-07:00

To write a paper using Latex under ubuntu

kile - good editor using KDE for latex
jabref - maintain reference bib file
jPicEdt - draw graph
RapidSVN - graphic svn client
meld - graphic diff tool
okular - document preview

To install all

sudo apt-get install kile jabref jpicedt rapidsvn meld okular
jPicEdt can be downloaded from here

Note rapidsvn does not use meld automatically, needs to configure manually

Install Skype

2009-10-23T09:48:00.000-07:00

download from here for 32-bit or here for 64-bit
sudo dpkg -i skype-ubuntu-intrepid_2.1.0.47-1_i386.deb

(Optional) To integrate skype with pidgin

sudo apt-get install pidgin skype4pidgin

Creating/Adding Swap on Fly

2009-10-23T09:35:00.000-07:00

Source is from here.

sudo dd if=/dev/zero of=/swap_file bs=1M count=1000
sudo chown root:root /swap_file
sudo chmod 600 /swap_file
sudo mkswap /swap_file
sudo swapon /swap_file
sudo gedit /etc/fstab

/swap_file none swap sw 0 0

Comments:

create a file named "swap_file" with size 1000MB
change the ownership to "root"
change the access so that it can be read and write by owner only
make it be to "swap" type
turn on the swap
edit the sytem file so that the swap is mounted when system is started

Installing Windows under Ubuntu -- QEMU

2009-09-07T02:18:00.000-07:00

Original source is from here.

*note: KQEMU is the QEMU Accelorator
REMEMBER: If it's not covered here RTFM....

Step 1) Compile and setup of Qemu and KQemu
Step 2) Installation of GuestOS [ Windows 98se in this example ]
Step 3) Setup of Tun/Tap network interface on host and guest OS.
Step 4) NAT setup to allow guestOS access to the internet.

Brief Description:
QEMU is an Open-Source Emulator that emulates x86 arch as well as several others.... allowing for guestOS's to be installed inside the host OS.
QEMU is available for Linux, Mac, and Windows. We'll be covering the Linux Package in this HowTo.
For more information on QEMU visit the projectpage @ http://fabrice.bellard.free.fr/qemu/

What you'll need:
+ QEMU source tarball from http://fabrice.bellard.free.fr/qemu/
+ KQEMU binary tarball from http://fabrice.bellard.free.fr/qemu/
+ linux-headers package
+ IPTables ( should already be installed ) package
+ libsdl1.2-dev package
+ Tun/Tap package
+ uml-utilities package
+ windows98 install cd and valid windows98 serial.
+ GCC-3.4 package

Ok, so this is the first HowTo i've wrote in quite a long time. First for ubuntu, and Qemu..

################################################## ##############
[ Step 1 ] - Compilation and Installation of KQEMU and QEMU

Outlined here is the steps taken to compile and setup Qemu and Kernel Module KQemu

A) Download the latest source tarball of QEMU from http://fabrice.bellard.free.fr/qemu/download.html current version is 0.8.1
B) Download the latest binary of KQEMU from http://fabrice.bellard.free.fr/qemu/qemu-accel.html

C) Move the tarballs to your /usr/local/src directory and deflate
#> sudo mv qemu-version.tar.gz /usr/local/src/
#> sudo mv kqemu-version.tar.gz /usr/local/src/

deflate...
#> sudo gunzip qemu-version.tar.gz; sudo tar -xvf qemu-version.tar
#> sudo gunzip kqemu-version.tar.gz; sudo tar -xvf kqemu-version.tar

D) Install linux-headers for your current kernel version.
If you don't know your current kernel version you can do `uname -r` at the shell to find out...

#> sudo apt-get install linux-headers-`uname -r`

E) Install GCC-3.4 [ qemu complains on GCC-4 ] and libsdl1.2-dev

#> sudo apt-get install gcc-3.4 libsdl1.2-dev

locate the installed gcc-3.4 binary using whereis
#> whereis gcc-3.4

it should be located in /usr/bin/ if not found at all installation failed. repeat step E.
make a note of it's location. you're going to need it in step F

F) Configure and Compile QEMU and KQEMU

change directories to your qemu-source you deflated in step C
#> cd /usr/local/src/qemu-version
#> sudo ./configure --cc=/usr/bin/gcc-3.4 [ remember the location of it from step E? ]

once configuration is completed run make and make install to compile and install... do so as follows

#> sudo make
#> sudo make install

verify that QEMU installed correctly...
#> whereis qemu

change directories to your kqemu-source you deflated in step C, and configure make and make install

#> cd /usr/local/src/kqemu-version
#> sudo ./configure
#> sudo make
#> sudo make install

verify that device node /dev/kqemu exists
if not...execute following commands

#> sudo mknod /dev/kqemu c 250 0
#> sudo chmod 666 /dev/kqemu

Active module KQEMU
#> sudo modprobe kqemu
Verify that it loaded properly
#> lsmod | grep kqemu
If it failed to show up. issue a dmesg | tail to see what the error was
#> dmesg | tail
Anyway... continuing...

[ Step 1 Completed ]
################################################## ################

[ Step 2 ] Installing Guest OS
*notes: you can use either the actual install CD or an ISO made from the original install disk, I used an iso.
you can also use the dd command with the seek option to create your hard disk image file, in place of qemu-img create
for convenience we're going to use the qemu-img binary installed with QEMU

*help: Run qemu/qemu-img without any arguements to view it's help

A) Create the Hard Drive Image File to use as HDA
choose the directory you wish to store your disk images you can use mkdir to create a new one. I use ~/qemu
#> cd ~/qemu
A brief rundown of what we're executing here....
qemu-img create [filename] [-f format( raw, vvfat, cloop,... )] [size G(gigs), M(megs) ]
#> qemu-img create win98.img -f raw 2G
Ok, we've created the 2G image file to install windows98se into....now we load QEMU to boot from the cdrom/iso file specified to start installation

#> qemu -hda win98.img -cdrom /dev/cdrom -boot d -localtime -net nic -net tap
Now QEMU should boot from CD, just follow the steps to complete the installation...

Once installation has completed now we can move onto Step 3
[ Step 2 Complete ]
################################################## ################

[ Step 3 ] Setting up TUN/TAP network interface on HostOS and GuestOS

A) Install uml-utilities via apt
#> sudo apt-get install uml-utilities
B) Load kernel module tun
#> sudo modprobe tun66.202.65.50
C) Create the /dev/net/tun device node
#> mkdir /dev/net
#> mknod /dev/net/tun c 10 200
D) Setup the tap0 interface, with an ip address i use 192.168.100.1 for this.
Create the tap0 interface using tunctl
#> sudo tunctl

Give it an IP-Address
#> sudo ifconfig tap0 192.168.100.1 up
Make sure it was configured properly...
#> ifconfig

You should see tap0 with an inet addr: 192.168.100.1 and a Mask: 255.255.255.0
If there is no mask set...sometimes this happens don't know why but it's happend....do this
#> sudo ifconfig tap0 192.168.100.1 netmask 255.255.255.0 up

Ok, we're done with the HOST side of this

E) Setting up the GuestOS's network configuration

If you don't have QEMU booted into windows already then do so by this command...
#> qemu -hda win98.img -boot c -net nic -net tap &

Once windows has loaded goto your Control panel and open Network Settings
At the configuration tab Select TCP/IP and click properties

In the Properties window
- Select the IP Address Tab
select specify an IP address
enter 192.168.100.2 as your ip address
enter 255.255.255.0 as your subnet mask
- Select the Gateway Tab
add a new gateway as 192.168.100.1
- Select Ok
Select Ok
Now you will be promted for a restart....restart and you should be able to ping the guestOS from the hostOS

F) Testing the network connection
from a terminal
#> ping 192.168.100.2 -c 4
You should reach 192.168.100.2 if not, verify you followed every step.

Make sure you can Ping the Host from the guest

on Windows from a dosprmpt
#> ping 192.168.100.1 -n 4
You should reach 192.168.100.1 if not, verify you followed every step correctly.

[ Step 3 Complete ]
################################################## ###############

[ Step 4 Setting up NAT to allow GuestOS access to the internet ]
*note: i'm going to go ahead and assume you have iptables already installed.

A) Load Required Kernel Modules
#> sudo modprobe ip_tables
#> sudo modprobe iptable_nat
#> sudo modprobe ip_nat_ftp
#> sudo modprobe ip_nat_irc

B) Enable IP-Forwarding
as root run
#> echo "1" > /proc/sys/net/ipv4/ip_forward

If you get your IP Address Dynamically e.g. PPP0 (Dial-up)
as root run
#> echo "1" > /proc/sys/net/ipv4/ip_dynaddr

Enable SNAT (MASQUERADE) functionality on eth0/ppp0
*note: replace eth0 with ppp0 for dialup

#> sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

C) Setup DNS on guestOS
*note: this is for windows98se, methods aren't listed for other OS's

You can retrieve your DNS Server Ip's from your /etc/resolv.conf file after connected to the internet.

#> sudo cat /etc/resolv.conf

In windows, goto control panel -> networking -> TCP/IP Properties -> DNS Configuration
Select Enable DNS

Set Host to your gateway address, i set mine to 192.168.100.1 for my gateway
Set Domain to your Domain i just set it to one of the DNS servers IP Address's
Add your ISP DNS Servers to the DNS List..

Ok, reboot! everything should work fine now..
[ Step 4 Complete ]

After following these steps you should have a working Qemu using the KQEMU accelerator as well as Tun/Tap Virtual Network forwarding Requests from the guest to the internet.
If something isn't working, double check to make sure you set it up correctly.

Check System

2009-09-07T02:08:00.000-07:00

Here I list some common commands used for checking system utilization:

top -- check the information of most resource consuming threads
cat /proc/cpuinfo -- check the CPU information
cat /proc/meminfo (or free -m) -- check the memory information
ps -- report a snapshot of the current processes
df -h -- check the disk information
du -h -- check the size of current directory
kill -- kill process, for example when some program is dead. use -9 to force kill, or pkill (program name) in case you can't find process id.

To be updated for more ...

ssh login without password

2009-07-03T05:04:00.000-07:00

First log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:

a@A:~> ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa):
Created directory '/home/a/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A

Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):

a@A:~> ssh b@B mkdir -p .ssh
b@B's password:

Finally append a's new public key to b@B:.ssh/authorized_keys and enter b's password one last time:

a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys'
b@B's password:

From now on you can log into B as b from A as a without password:

a@A:~> ssh b@B hostname
B

Eclipse with C++

2009-06-04T23:39:00.000-07:00

In ubuntu,

sudo apt-get install eclipse eclipse-cdt

A script to downgrade svn versions

2009-06-03T20:27:00.000-07:00

I got an error saying "This client is too old to work with working copy '...' ". How can I fix it without upgrading Subversion?

Sometimes the working copy metadata format changes incompatibly between minor releases. For example, say you have a working copy created with Subversion 1.4.4, but one day you decide to try out Subversion 1.5.0. Afterwards, you attempt to switch back to 1.4.4, but it doesn't work — it just gives the above error.

This is because 1.5.0 upgraded your working copy format to support some new features (in this case, changelists, the keep-local flag, and variable-depth directories). Although 1.4.4 doesn't know anything about these new features, it can at least recognize that the working copy format has been upgraded to something higher than it can handle.

1.5.0 upgraded the working copy for a good reason: it realizes that 1.4.4 does not know about these new features, and that if 1.4.4 were to meddle with the working copy metadata now, important information might be lost, possibly causing corruption (see issue #2961, for example).

But this automatic upgrade behavior can be annoying, if you just want to try out a new release of Subversion without installing it permanently. For this reason, we distribute a script that can downgrade working copies when doing so is safe:

http://svn.collab.net/repos/svn/trunk/tools/client-side/change-svn-wc-format.py

Run that script with the "--help" option to see how to use it. As future versions of Subversion are released, we will try to keep this FAQ entry up-to-date with potential downgrade scenarios and their implications.

Evolution - Global Catalog server name

2009-06-03T20:04:00.000-07:00

To discover the Global Address List/Active Directory in Outlook:

Open a new email message in Outlook.
Click on the "To:" button to get the "Select Names" dialog
Put "Show Names from the" to "Global Address List".
Right-click on the "Global Address List" to get "Properties". This opens a dialog with the name of the Global Address List server and the path. You just need the server name.