Tutorial Proggraming Free

tutorial - What are TCP control bits

There are six ‘control bits’ defined in TCP, one or more of which is defined in each packet. The control bits are ‘SYN’, ‘ACK’, ‘PSH’, ‘URG’, ‘RST’, and ‘FIN’. TCP uses these bits to define the purpose and contents of a packet.

SYN bit is used in establishing a TCP connection to synchronize the sequence numbers between both endpoints.

ACK bit is used to acknowledge the remote host’s sequence numbers, declaring that the information in the acknowledgment field is valid.

PSH flag is set on the sending side, and tells the TCP stack to flush all buffers and send any outstanding data up to and including the data that had the PSH flag set. When the receiving TCP sees the PSH flag, it too must flush its buffers and pass the information up to the application.

URG bit indicates that the urgent pointer field has a valid pointer to data that should be treated urgently and be transmitted before non-urgent data.

RST bit tells the receiving TCP stack to immediately abort the connection.

FIN bit is used to indicate that the client will send no more data (but will continue to listen for data).

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source:http://linuxpoison.blogspot.com/2007/11/13578175806704.html

tutorial - HowTo chang the file modification time

Use touch to change a file’s timestamp without modifying its contents. Give the name of the file to be changed as an argument. The default action is to change the timestamp to the current time.

* To change the timestamp of file `nikesh’ to the current date and time, type:

$ touch nikesh

To specify a timestamp other than the current system time, use the `-d’ option, followed by the date and time that should be used enclosed in quote characters. You can specify just the date, just the time, or both.

* To change the timestamp of file `nikesh’ to `17 May 2006 14:16′, type:

$ touch -d ‘17 May 2006 14:16′ nikesh

* To change the timestamp of file `nikesh’ to `14 May’, type:

$ touch -d ‘14 May’ nikesh

* To change the timestamp of file `nikesh’ to `14:16′, type:

$ touch -d ‘14:16′ nikesh

source:http://linuxpoison.blogspot.com/2007/11/13578175801881.html

tutorial - Add Microsoft True Type Fonts into Linux

If you are a regular user of windows and have switched to linux recently, then sure you are going to miss some important things from your windows machine. One such things is those beautiful fonts which you have used in windows.

Method 1:
For installing these fonts there various methods available one among them is as below,

* Install a Cab Extract Utility for Linux. Get it from http://www.cabextract.org.uk/
* Download the Latest msttcorefonts spec from http://corefonts.sourceforge.net/
* If you have RPM Build environment in your home directory, then go ahead with the command. rpmbuild -bb msttcorefonts-2.0-1.spec
* Install the newly built rpm using the following command rpm -ivh <>
* Once done, log off & log in or restart the xfs service using the command /sbin/service xfs reload

Method 2:
use RPM method,

* rpm -ivh msttcorefonts-2.0-1.noarch.rpm

You should be logged in as a super user or use sudo

source:http://linuxpoison.blogspot.com/2007/11/13578175808362.html

tutorial - HowTo Add PATH

To add or remove a directory in your path, use a text editor to change the shell variable `PATH’ in the `.bashrc’ file in your home directory

For example, suppose the line that defines the `PATH’ variable in your `.bashrc’ file looks like this:

PATH="/usr/bin:/bin:/usr/bin/X11:/usr/games"

You can add the directory `/home/nikesh/bin’ to this path, by editing this line like so:

PATH="/usr/bin:/bin:/usr/bin/X11:/usr/games:/home/nikesh/bin"

source:http://linuxpoison.blogspot.com/2007/11/135781758019976.html

tutorial - Make fetchmail deliver via procmail

Just add the following line:

mda “/usr/bin/procmail -d %T”

to your “options” in ~/.fetchmailrc For instance .fetchmailrc may look something like:

poll mail.domain.com protocol pop3 username myusername password mysecretpassword options ssl mda “/usr/bin/procmail -d %T”

source:http://linuxpoison.blogspot.com/2007/12/135781758014989.html

tutorial - Filter attachments (.bat, .exe, etc..) in postfix

Simple, In /etc/postfix/main.cf enable the body checks with this line:

body_checks = pcre:/etc/postfix/body_checks

Now put something in this file (/etc/postfix/body_checks):

/^(.*)name=\”(.*).(hta|vb[esx]|ws[fh]|js[e]|bat|cmd)\”$/ REJECT

This will filter attachments of various types. Remove from the above line,

whatever you want to allow.Of course you can add some more lines to make postfix a simple spam filter:

/special offer email/ REJECT
/mortgage rates/ REJECT
/other spam mail subjects/ REJECT

source:http://linuxpoison.blogspot.com/2007/12/135781758014216.html

tutorial - HowTo do Transparent proxy with Squid

Modify or add following to squid configuration file (/etc/squid/squid.conf):

httpd_accel_host virtual httpd_accel_port 80 httpd_accel_with_proxy on httpd_accel_uses_host_header onacl lan src 192.168.1.1 192.168.2.0/24 http_access allow localhost http_access allow lan
Added following rules to forward all http requests (coming to port 80) to the Squid server port 3128 :

[eth0 connected to internet and eth1 connected to local lan]

iptables -t nat -A PREROUTING -i eth1 -p tcp –-dport 80 -j DNAT –to 192.168.1.1:3128 iptables -t nat -A PREROUTING -i eth0 -p tcp –-dport 80 -j REDIRECT –-to-port 3128

source:http://linuxpoison.blogspot.com/2007/12/1357817580903.html

tutorial - How To Apply Patch to Kernel Source

Go to directory which holds the kernel source code

# cd /usr/src/linux
# bzip2 -dc /usr/src/patch-x.y.z.bz2 patch -p1 –dry-run

–dry-run option to check that the patch applies cleanly. It can be a real pain to pull out a partially-applied patch. The -p1 option strips off part of the diff file’s pathnames for each changed file (see the patch(1) manpage for more details).

Now you’ve checked that it should apply cleanly, run the following to actually apply it. Then you’re done!

# bzip2 -dc /usr/src/patch-x.y.z.bz2 patch -p1

source:http://linuxpoison.blogspot.com/2007/12/135781758015750.html

tutorial - All 235 low-cost webcams supported in Linux thanks to... this man

LONE HOBBYIST programmer sitting at his home in France is responsible for adding 235 USB webcams to the list of those supported by Linux.

His name is Michel Xhaard

Check his site : here
List of supported webcams : here

source:http://linuxpoison.blogspot.com/2007/12/135781758019620.html

tutorial - HowTo Convert CHM files to PDF in Linux

1. Download chm2pdf by clicking [Here].

3. Now extract the downloaded file.

4. Open your Terminal and browse to the folder you extracted and run:

5. sudo python setup.py install

Now to use it is very simple:

In Terminal, type: chm2pdf filename.chm

Dependencies

You need these packages installed and working:

* chmlib
* pychm
* htmldoc

source:http://linuxpoison.blogspot.com/2007/12/135781758017783.html

tutorial - They are Computer GODS

1) Dennis Ritchie and Ken Thompson - Dennis was the original developer of C and one of the core developers on UNIX while Ken was the man responsible for UNIX

2) Bjarne Stroustrup - This guy brought us C++! I couldn't talk trash about a guy who made C++.

3) Alan Kay - This is one of the fathers of object oriented

programming.

4) John McCarthy - The original designer of the Lisp programming language.

5) Richard Stallman - Like him or hate him, he is a seriously influential person in the computer world, The man is the founder of GNU.

6) Larry Wall - This guy brought us Perl.

7) Alan Cox - Alan Cox and Richard Stallman must have been long lost brothers. This guy was one of the earliest developers on the linux kernel and apparently has not shaved since he started.

8) James Gosling - This guy brought us Java and is wearing a shirt with the java mascot playing an electric guitar.

9) Guido Van Rossum - This guy brought us Python

10) Linus Benedict Torvalds: Best known for initiating the development of the Linux kernel.

11) Dr. Andrew Stuart "Andy" Tanenbaum : He is best known as the author of MINIX, a free Unix-like operating system for teaching purposes, and for his computer science textbooks, regarded as standard texts in the field. He regards his teaching job as his most important work.

Am I missing anyone here?

source:http://linuxpoison.blogspot.com/2007/12/13578175805391.html

tutorial - Quick Log server configuration

On remote server: edit /etc/sysconfig/syslog on the server and set

SYSLOGD_PARAMS=”-r”

The -r option allows remote machine to log to syslog.

On the client machine, edit /etc/syslog.conf and add the line(s)

*.*  @server

Don’t forget to restart the syslog on both machines after the above editing.

source:http://linuxpoison.blogspot.com/2007/12/13578175804031.html

tutorial - UNIX history in form of picture

source:http://linuxpoison.blogspot.com/2007/12/135781758011400.html

tutorial - HowTo Identify your Modem chipset

# Download http://easylinux.info/uploads/scanModem.gz

# gunzip -c scanModem.gz > scanModem
# chmod +x scanModem
# cp scanModem /usr/bin/To identify Modem chipset
# scanModem# gedit Modem/ModemData.txt

source:http://linuxpoison.blogspot.com/2007/12/1357817580529.html

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