802.11 Frames

Current 802.11 standards define "frame" types for use in transmission of data as well as management and control of wireless links.

Frames are divided into very specific and standardized sections. Each frame has a MAC header, payload and FCS. Some frames may not have payload portion. First 2 bytes of MAC header is a frame control field that provides detailed information about the frame. The sub fields of the frame control field is presented in order.

* Protocol Version: It is two bits in size and represents the protocol version. Currently used protocol version is zero. Other values are reserved for future use.

* Type: It is two bits in size and helps to identify the type of WLAN frame. Control, Data and Management are various frame types defined in IEEE 802.11.
* Sub Type: It is four bits in size. Type and Sub type are combined together to identify the exact frame.

* ToDS and FromDS: Each is one bit in size. They indicate whether a data frame is headed for a distributed system. Control and management frames set these values to zero. All the data frames will have one of these bits set. However communication within an IBSS network always set these bits to zero.

* More Fragment: The More Fragmentation bit is set most notably when higher level packets have been partitioned and will be set for all non-final sections. Some management frames may require partitioning as well.

* Retry: Sometimes frames require retransmission, and for this there is a Retry bit which is set to one when a frame is resent. This aids in the elimination of duplicate frames.

* Power Management: The Power Management bit indicates the power management state of the sender after the completion of a frame exchange. Access points are required to manage the connection and will never set the power saver bit.

* More Data: The More Data bit is used to buffer frames received in a distributed system. The access point uses this bit to facilitate stations in power saver mode. It indicates that at least one frame is available and addresses all stations connected.

* WEP: The WEP bit is modified after processing a frame. It is toggled to one after a frame has been decrypted or if no encryption is set it will have already been one.

* Order: This bit is only set when the "strict ordering" delivery method is employed. Frames and fragments are not always sent in order as it causes a transmission performance penalty.

The next two bytes are reserved for the Duration ID field. This field can take one of three forms: Duration, Contention-Free Period (CFP), and Association ID (AID).

An 802.11 frame can have up to four address fields. Each field can carry a MAC address. Address 1 is the receiver, Address 2 is the transmitter, Address 3 is used for filtering purposes by the receiver.

* The Sequence Control field is a two-byte section used for identifying message order as well as eliminating duplicate frames. The first 4 bits are used for the fragmentation number and the last 12 bits are the sequence number.
* An optional two-byte Quality of Service control field which was added with 802.11e.
* The Frame Body field is variable in size, from 0 to 2304 bytes plus any overhead from security encapsulation and contains information from higher layers.
* The Frame Check Sequence (FCS) is the last four bytes in the standard 802.11 frame. Often referred to as the Cyclic Redundancy Check (CRC), it allows for integrity check of retrieved frames. As frames are about to be sent the FCS is calculated and appended. When a station receives a frame it can calculate the FCS of the frame and compare it to the one received. If they match, it is assumed that the frame was not distorted during transmission.[18]

Management Frames allow for the maintenance of communication. Some common 802.11 subtypes include:

* Authentication frame: 802.11 authentication begins with the WNIC sending an authentication frame to the access point containing its identity. With an open system authentication the WNIC only sends a single authentication frame and the access point responds with an authentication frame of its own indicating acceptance or rejection. With shared key authentication, after the WNIC sends its initial authentication request it will receive an authentication frame from the access point containing challenge text. The WNIC sends an authentication frame containing the encrypted version of the challenge text to the access point. The access point ensures the text was encrypted with the correct key by decrypting it with its own key. The result of this process determines the WNIC's authentication status.
* Association request frame: sent from a station it enables the access point to allocate resources and synchronize. The frame carries information about the WNIC including supported data rates and the SSID of the network the station wishes to associate with. If the request is accepted, the access point reserves memory and establishes an association ID for the WNIC.
* Association response frame: sent from an access point to a station containing the acceptance or rejection to an association request. If it is an acceptance, the frame will contain information such an association ID and supported data rates.
* Beacon frame: Sent periodically from an access point to announce its presence and provide the SSID, and other parameters for WNICs within range.
* Deauthentication frame: Sent from a station wishing to terminate connection from another station.
* Disassociation frame: Sent from a station wishing to terminate connection. It's an elegant way to allow the access point to relinquish memory allocation and remove the WNIC from the association table.
* Probe request frame: Sent from a station when it requires information from another station.
* Probe response frame: Sent from an access point containing capability information, supported data rates, etc., after receiving a probe request frame.
* Reassociation request frame: A WNIC sends a reassociation request when it drops from range of the currently associated access point and finds another access point with a stronger signal. The new access point coordinates the forwarding of any information that may still be contained in the buffer of the previous access point.
* Reassociation response frame: Sent from an access point containing the acceptance or rejection to a WNIC reassociation request frame. The frame includes information required for association such as the association ID and supported data rates.

Control frames facilitate in the exchange of data frames between stations. Some common 802.11 control frames include:

* Acknowledgement (ACK) frame: After receiving a data frame, the receiving station will send an ACK frame to the sending station if no errors are found. If the sending station doesn't receive an ACK frame within a predetermined period of time, the sending station will resend the frame.
* Request to Send (RTS) frame: The RTS and CTS frames provide an optional collision reduction scheme for access point with hidden stations. A station sends a RTS frame to as the first step in a two-way handshake required before sending data frames.
* Clear to Send (CTS) frame: A station responds to an RTS frame with a CTS frame. It provides clearance for the requesting station to send a data frame. The CTS provides collision control management by including a time value for which all other stations are to hold off transmission while the requesting stations transmits.

----------------------

Management Frames

Management frames establish communications between stations and access points. They support Power Management and Contention Free modes. MAC management frames are also called MAC Management Protocol Data Units (MMPDUs). Management frames provide such services as authentication, association, and reassociation. Management frame bodies are never relayed through an access point. Instead they are “sourced” (generated) and sunk (read and disposed of) at the MAC layer, and therefore are never passed to the distribution system service or LLC. The Address 4 field is never used in an MMPDU. Unicast MMPDUs may be acknowledged, retransmitted, and fragmented^[1]. Figure 6.1 depicts the common format of all management frames.

Figure 6.1: MMPDU Frame Structure

Association Request Frame

A station will send an Association Request frame to an access point if it wants to associate with that access point. This frame exchange sequence ends successfully with an acknowledgement. A station becomes associated with an access point after the access point responds with an acceptance.

Figure 6.2: Association Request Frame Body Contents

Association Response Frame

After an access point receives an Association Request frame and acknowledges it, the access point will send an Association Response frame to indicate whether or not it is accepting the association with the requesting station. This second frame exchange sequence ends successfully with an acknowledgment. The Association Response frame provides the status (acceptance or rejection) and an AID (if the association was accepted).

Figure 6.3: Association Response Frame Body Contents

Reassociation Request Frame

A station will send a Reassociation Request frame to an access point if it already associated to the ESS and wants to reassociate to the ESS through another access point. This frame exchange sequence is ended successfully with an acknowledgment. A reassociation may occur if a station moves out of range from one access point and within range of another access point. The station will need to reassociate (not merely associate) with the new access point so that the new access point knows that it will need to negotiate the forwarding of data frames from the old access point and update its association table. Notice in Figure 6.4 that the Current AP Address (old AP address) fixed field is part of the Reassociation Frame.

Figure 6.4: Reassociation Request Frame Body Contents

Reassociation Response Frame

After an access point receives a Reassociation Request frame, the access point will send a Reassociation Response frame to indicate whether or not it is accepting the reassociation with the sending station. This frame exchange sequence is ended successfully with an acknowledgment. Reassociation is dependent on authentication with/through the new access point. If the reassociation is successful, the new access point will indicate this status in the status code element and include a unique AID for this station to use if operating in Power Save Poll mode.

Figure 6.5: Reassociation Response Frame Body Contents

Probe Request Frame

A station sends a Probe Request frame to obtain information from another station or access point. For example, a station may send a Probe Request frame to determine whether a certain access point is available. Mobile stations use Probe Request frames as part of the active scanning process.

Figure 6.6: Probe Request Frame Body Contents

Probe Response Frame

If a station or access point receives a Probe Request frame, the station will respond to the requesting station with a Probe Response frame containing specific parameters about itself. All access points and the station which last generated the beacon frame (if operating as an IBSS) can respond to probe requests with Probe Response frames.

Figure 6.7: Probe Response Frame Body Contents

Beacon Frame

An access point (or mobile station in an Ad Hoc network) periodically sends a beacon frame at a rate based on the aBeaconPeriod parameter in the MIB. The beacon provides synchronization among stations of a BSS, and includes a timestamp that all stations within its BSS use to update what 802.11 defines as a timing synchronization function (TSF) timer. The TSF is basically a station’s internal 802.11 clock. The Probe Response frame and beacon frame are identical, except that the beacon also carries the traffic indication map (TIM) information element.

If the access point supports the Point Coordination Function, then it uses a beacon frame to announce the beginning of a contention-free period. If the network is an independent BSS (that is, it has no access points), all stations periodically send beacons for synchronization purposes.

Figure 6.8: Beacon Frame Body Contents

ATIM Frame

In an IBSS a station with frames buffered for other stations sends an Announcement Traffic Indication Message (ATIM) frame to each of these stations during the ATIM window, which immediately follows a beacon transmission in Ad Hoc mode. The station that sent the ATIM then transmits the buffered frames to the applicable recipients during a data window. The transmission of the ATIM frame alerts stations in powersave mode to stay awake long enough to solicit and receive their respective frames. The ATIM frame body is null.

Disassociation Frame

If a station or access point wants to terminate an association, it will send a Disassociation frame to the other station that is part of the association. A single Disassociation frame sent to the broadcast address by an access point can terminate associations with more than one station at a time.

Figure 6.9: Disassociation Frame Body

Authentication Frame

A station sends an Authentication frame to an access point that it wants to authenticate with. The authentication process consists of the transmission of two or four authentication frames, depending on the type of authentication being implemented, Open System or Shared Key respectively. If Shared Key, the third authentication frame of the four is WEP encrypted. Each authentication frame requires an acknowledgment.

Figure 6.10: Authentication Frame Body

Deauthentication Frame

A station sends a Deauthentication frame to a station or access point with which it wants to terminate communications.

Figure 6.11: Deauthentication Frame Structure

Management Frame Summary

The chart below provides a quick reference to the contents and sizes (in octets) of each management frame type per the 802.11 series of standards).

Figure 6.12: Management Frame Quick Reference Chart

Thanks to :
http://www.sss-mag.com/pdf/802_11tut.pdf
http://en.wikipedia.org/wiki/IEEE_802.11
http://www.wireless-net.org/McGraw.Hill-CWAP.Certified.Wir/8156final/LiB0061.html

shell script for enabling sniffer mode in wire shark

shell script for enabling sniffer mode in wire shark
--------------------------------------------
#! /bin/sh
sudo ifconfig wlan8 down
sudo iwconfig wlan8 mode monitor
echo "Enter Ch no. "
read ch_no
sudo iwconfig wlan8 ch $ch_no
#echo $ch_no
sudo ifconfig wlan8 up
sudo wireshark
----------------------------------------------

For personal customization of .emacs file

Missing .emacs file
Missing emacs init file

you can't find your .emacs file anywhere in your system. You've already looked in you home directory and it's nowhere to be found. Could somebody help me out?

So the solution is here.

There are two main versions of emacs - emacs and Xemacs and I don't think that either of them creates a .emacs file automatically - you have to create your own.

So what do you put in your .emacs? There are lots of examples of .emacs's that you can google for on the net, but here's one to start you off...
http://www.dotemacs.de/dotfiles/sample.emacs.html
...just save it to .emacs in your home directory.

If you have Xemacs installed, they don't use a file called .emacs but create a directory called .xemacs. Inside that directory you create a file called custom.el and that functions as your .emacs.

location of .emacs file :
/home/yourname/.emacs

eg: /home/siva/.emacs

Then add according to your need of your choice in emacs and save the file

sample .emacs file
;--------------------------

;displays the time in the status bar
(display-time)

;show paren, brace, and curly brace "partners" at all times
(show-paren-mode t)

;displays the battery power of laptop
(display-battery-mode)

;menu bar mode disable
(menu-bar-mode)

;status bar
(set-face-foreground 'modeline "blue")

;status bar
(set-face-background 'modeline "white")

;-------------------

ADB shell

What is ADB

ADB (Android Debug Bridge) is a tool that comes with the Android SDK that allows you to control and interface with your Android device. It is located in the tools folder when you unpack the SDK.

Source: ADB
Commands

Adb has many built in commands. Some are interactive (meaning they keep running until you stop them) and some just perform a simple task. Below is a list of the commands in the 1.0 SDK version of adb.

Android Debug Bridge version 1.0.20

-d - directs command to the only connected USB device
returns an error if more than one USB device is present.
-e - directs command to the only running emulator.
returns an error if more than one emulator is running.
-s - directs command to the USB device or emulator with
the given serial number
-p - simple product name like 'sooner', or
a relative/absolute path to a product
out directory like 'out/target/product/sooner'.
If -p is not specified, the ANDROID_PRODUCT_OUT
environment variable is used, which must
be an absolute path.
devices - list all connected devices

device commands:
adb push - copy file/dir to device
adb pull - copy file/dir from device
adb sync [ ] - copy host->device only if changed
(see 'adb help all')
adb shell - run remote shell interactively
adb shell - run remote shell command
adb emu - run emulator console command
adb logcat [ ] - View device log
adb forward - forward socket connections
forward specs are one of:
tcp:
localabstract:
localreserved:
localfilesystem:
dev:
jdwp: (remote only)
adb jdwp - list PIDs of processes hosting a JDWP transport
adb install [-l] [-r] - push this package file to the device and install it
('-l' means forward-lock the app)
('-r' means reinstall the app, keeping its data)
adb uninstall [-k] - remove this app package from the device
('-k' means keep the data and cache directories)
adb bugreport - return all information from the device
that should be included in a bug report.

adb help - show this help message
adb version - show version num

DATAOPTS:
(no option) - don't touch the data partition
-w - wipe the data partition
-d - flash the data partition

scripting:
adb wait-for-device - block until device is online
adb start-server - ensure that there is a server running
adb kill-server - kill the server if it is running
adb get-state - prints: offline | bootloader | device
adb get-product - prints:
adb get-serialno - prints:
adb status-window - continuously print device status for a specified device
adb remount - remounts the /system partition on the device read-write

networking:
adb ppp [parameters] - Run PPP over USB.
Note: you should not automatically start a PDP connection.
refers to the tty for PPP stream. Eg. dev:/dev/omap_csmi_tty1
[parameters] - Eg. defaultroute debug dump local notty usepeerdns

adb sync notes: adb sync [ ]
can be interpreted in several ways:

- If is not specified, both /system and /data partitions will be updated.

- If it is "system" or "data", only the corresponding partition
is updated.

Common Use

Some of the more common commands in adb are push, pull, shell, install, remount, and logcat.

Push sends a file from your desktop computer to your Android device:

adb push test.txt /sdcard/test.txt

Pull pulls a file from your Android device to your desktop computer:

adb pull /sdcard/test.txt test.txt

Shell lets you run an interactive shell (command prompt) on the Android device:

adb shell

Install lets you install an android APK file to your Android device:

adb install myapp.apk

Remount remounts the /system partition as writable (or readonly if it is already writeable):

adb remount

Logcat lets you view the devices debug logs in real time (must press control+c to exit):

adb logcat


----------------

Through ADB

Pull apps off phone onto computer
Code:

adb pull /system/sd/app app
adb pull /system/sd/app-private app-private

Push apps back to phone from the computer
Code:

adb push app /system/sd/app
adb push app-private /system/sd/app-private

Delete existing apps on SD
Code:

adb shell rm -r /system/sd/app
adb shell rm -r /system/sd/app-private


Through Terminal

Partition SD card - This erases everything on your SD card (*size* being the size of the FAT32 partition)
Code:

$ su
# cd /data
# wget http://64.105.21.209/bin/lib/droid/sdsplit
# chmod 555 sdsplit
# /data/sdsplit -fs *size* (add -nc to the end for JFv1.5ADP)


From the Recovery Screen

Sending an update file to your SD card:
Code:

adb shell mount /sdcard
adb shell rm /sdcard/update.zip
adb push *filename* /sdcard/update.zip


From Fastboot

Restoring a nandroid backup - Start command-prompt/terminal cd to the nandroid folder and enter following commands
Code:

fastboot erase boot
fastboot erase recovery
fastboot flash system system.img
fastboot flash boot boot.img
fastboot flash userdata data.img
fastboot flash recovery recovery.img
fastboot reboot

------------

Basic Android Terminal and ADB Shell Command List

1. How to open a cmd in Android Phone
Method 1: “Start” – “”Program”-” “Accessories” – “” Command Prompt ”
Method 2: “Start” – “” Run “, type cmd ENTER

2. How to restart Android Phone
When the phone and Computer is connected to the data cable, you can enter the following command
view source
print?
1 adb shell reboot === ENTER

3. Restart Android into Recovery Mode
With the data cable connected to your phone and computer, enter the following command
view source
print?
1 adb shell reboot recovery === ENTER

4. Convert back to ext2 partition
Restart the phone into Recovery mode, press “Alt + X” into the console. Open cmd and enter the following command
view source
print?
1 adb shell === ENTER
2 tune2fs-O ^ has_journal / dev/block/mmcblk0p2 === carriage return
3 e2fsck / dev/block/mmcblk0p2 === carriage return (optional, can be a problem area in section 2, when used)

5. Pulling applications from Android phone to computer
view source
print?
1 adb pull /system/sd/app app
2 adb pull /system/sd/app-private app-private

6. Pushing applications back to android phone from the computer
view source
print?
1 adb push app /system/sd/app
2 adb push app-private /system/sd/app-private

7. Delete existing apps on Android SD
view source
print?
1 adb shell rm -r /system/sd/app
2 adb shell rm -r /system/sd/app-private

8. Repair gravity System or switch to screen
Sometimes frequent brushing of phone can cause gravity system or switch to screen failure. Just follow the steps below-
Restart the phone into Recovery mode, press “Alt + X” into the console
Open cmd and enter the following command
view source
print?
1 mount / data === carriage return
2 rm / data / misc / akmd * / data / misc / rild * === ENTER

9. Ext2/ext3/ext4 formatted partition
Enter the following command in the cmd
view source
print?
1 adb remount === ENTER
2 adb shell === ENTER
3 rm-r / system / sd / * === carriage return

10. Remove/ system / app under the application
Under normal circumstances / system / app is not under an application. Use the following methods to remove these applications.
Open cmd and enter the following command
view source
print?
1 adb remount === ENTER
2 adb rm / system / app / Stocks.apk === Enter

11. If the start Time is too Long
Just enter the following command in order to view the boot process.
view source
print?
1 adb logcat === ENTER

12. Through Terminal Partition SD card
It will erase everything on your SD card
view source
print?
1 $ su
2 # cd /data
3 # wget http://64.105.21.209/bin/lib/droid/sdsplit
4 # chmod 555 sdsplit
5 # /data/sdsplit -fs *size* (add -nc to the end for JFv1.5ADP)

13. From the Recovery Screen, send an update file to your SD card.
view source
print?
1 adb shell mount /sdcard
2 adb shell rm /sdcard/update.zip
3 adb push *filename* /sdcard/update.zip

14. Restoring a nandroid backup via Fastboot
Start command-prompt/terminal cd to the nandroid folder and enter following commands
view source
print?
1 fastboot erase boot
2 fastboot erase recovery
3 fastboot flash system system.img
4 fastboot flash boot boot.img
5 fastboot flash userdata data.img
6 fastboot flash recovery recovery.img
7 fastboot reboot

15. Clear Search History in Android

Search History is accounted for Mobile Memory. It can also leak your privacy information as well. Just follow the steps below to clear android history.

Steps are as follows:

1. Make sure your mobile phone has Root authority.
2. Open the super-terminal.
3. Enter the following command
view source
print?
1 su
2 rm / data / data / com.android.vending / databases / suggestions.db

4. Exit Hyper Terminal and restart the phone.


Thanks to :
http://forum.xda-developers.com/showthread.php?t=517874
http://www.gadgetsdna.com/android-terminal-adb-shell-command-list/1168/
http://android-dls.com/wiki/index.php?title=ADB

Get familiar with the VIM editor

Get familiar with the VIM editor

This text will provide you information about the Linux / Unix vi text editor and it's options.


SYNTAX

vi [ -| -s ] [-l] [-L] [-R] [ -r [ filename ] ] [-S] [-t tag] [-v] [-V] [-x] [-w] [-n ] [-C] [+command | -c command ] filename

- | -s Suppress all interactive user feedback. This is useful when processing editor scripts.

-l Set up for editing LISP programs.

-L List the name of all files saved as the result of an editor or system crash.

-R Readonly mode; the readonly flag is set, preventing accidental overwriting of the file.

-r filename Edit filename after an editor or system crash. (Recovers the version of filename that was in the buffer when the crash occurred.)

-S This option is used in conjunction with the -t tag option to tell vi that the tags file may not be sorted and that, if the binary search (which relies on a sorted tags file) for tag fails to find it, the much slower linear search should also be done. Since the linear search is slow, users of large tags files should ensure that the tags files are sorted rather than use this flag. Creation of tags files normally produces sorted tags files. See ctags for more information on tags files.

-t tag Edit the file containing the tag, tag, and position the editor at its definition.

-v Start up in display editing state using vi . You can achieve the same effect by simply typing the vi command itself.

-V Verbose. When ex commands are read by means of standard input, the input will be echoed to standard error. This may be useful when processing ex commands within shell scripts.

-x Encryption option; when used, vi simulates the X command of ex and prompts the user for a key. This key is used to encrypt and decrypt text using the algorithm of the crypt command. The X command makes an educated guess to determine whether text read in is encrypted or not. The temporary buffer file is encrypted also, using a transformed version of the key typed in for the -x option. If an empty encryption key is entered (that is, if the return key is pressed right after the prompt), the file will not be encrypted. This is a good way to decrypt a file erroneously encrypted with a mistyped encryption key, such as a backspace or undo key.

-wn Set the default window size to n. This is useful when using the editor over a slow speed line.

-C Encryption option; same as the -x option, except that vi simulates the C command of ex . The C command is like the X command of ex , except that all text read in is assumed to have been encrypted.

+command | -c command Begin editing by executing the specified editor
command (usually a search or positioning command).
filename The file to be edited.


USER COMMANDS

Arrow keys Move cursor

hjkl Same as arrow keys

itextESC Insert text

cwnewESC Change word to new

easESC pluralize word (end of word; append s; escape from input state)

x delete a character

dw delete a word

dd delete a line

3dd deletes 3 lines

u undo previous change

ZZ exit vi , saving changes

:q!CR quit, discarding changes

/textCR search for text

^U ^D scroll up or down

:cmdCR any ex or ed command

ESC end insert or incomplete command

DEL (delete or rubout) interrupts

:wCR write back changes

:w!CR forced write, if permission originally not valid

:qCR quit

:q!CR quit, discard changes

:e nameCR edit file name

:e!CR reedit, discard changes

:e + nameCR edit, starting at end

:e +nCR edit, starting at line n

:e #CR edit alternate file

:e! #CR edit alternate file, discard changes

:w nameCR write file name

:w! nameCR overwrite file name

:shCR run shell, then return

:!cmdCR run cmd, then return

:nCR edit next file in arglist

:n argsCR specify new arglist

^G show current file and line

:ta tagCR position cursor to tag

F forward screen

^B backward screen

^D scroll down half screen

^U scroll up half screen

nG go to the beginning of the specified line (end default), where n is a line number

/pat next line matching pat

?pat previous line matching pat

n repeat last / or ? command

N reverse last / or ? command

/pat/+n nth line after pat

?pat?-n nth line before pat

]] next section/function

[[ previous section/function

( beginning of sentence

) end of sentence

{ beginning of paragraph

} end of paragraph

% find matching ( ) or { }

^L clear and redraw window

^R clear and redraw window if ^L is -> key

zCR redraw screen with current line at top of window

z-CR redraw screen with current line at bottom of window

z.CR redraw screen with current line at center of window

/pat/z-CR move pat line to bottom of window

zn.CR use n-line window

^E scroll window down one line

^Y scroll window up one line

`` move cursor to previous context

\'\' move cursor to first non-white space in line

mx mark current position with the ASCII lower-case letter x

`x move cursor to mark x

\'x move cursor to first non-white space in line marked by x

H top line on screen

L last line on screen

M middle line on screen

+ next line, at first non-white space character

- previous line, at first non-white space character

CR return, same as +

down-arrow or j next line, same column

up-arrow or k previous line, same column

^ first non-white space character

0 beginning of line

$ end of line

l or -> forward

h or <- backward

^H same as <- (backspace)

space same as -> (space bar)

fx find next x

Fx find next x

tx move to character following the next x

Tx move to character following the previous x

; repeat last f, F, t, or T

, repeat inverse of last f, F, t, or T

n| move to column n

% find matching ( ) or { }

w forward a word

b back a word

e end of word

) to next sentence

} to next paragraph

( back a sentence

{ back a paragraph

W forward a blank-delimited word

B back a blank-delimited word

E end of a blank-delimited word

^H erase last character (backspace)

^W erase last word

erase your erase character, same as ^H (backspace)

kill your kill character, erase this line of input

\\ quotes your erase and kill characters

ESC ends insertion, back to command mode

CTRL-C interrupt, suspends insert mode

^D backtab one character; reset left margin of autoindent

^^D caret (^) followed by control-d (^D); backtab to beginning of line; do not reset left margin of autoindent

0^D backtab to beginning of line; reset left margin of autoindent

^V quote non-printable character

a append after cursor

A append at end of line

i insert before cursor

I insert before first non-blank

o open line below

O open line above

rx replace single character with x

RtextESC replace characters

d delete

c change

y yank lines to buffer

> left shift

< right shift

! filter through command

C change rest of line (c$)

D delete rest of line (d$)

s substitute characters (cl)

S substitute lines (cc)

J join lines

x delete characters (dl)

X delete characters before cursor dh)

Y yank lines (yy)

3yy yank 3 lines

3yl yank 3 characters

p put back text after cursor

P put back text before cursor \" .nr )I xp\"n

put from buffer x \" .nr )I xy\"n

yank to buffer x \" .nr )I xd\"n

delete into buffer x

u undo last change

U restore current line

. repeat last change \" .nr )I dp\"n

retrieve d\'th last delete

Linux: How to check the hardware

Linux: How to check the hardware

I've noticed there are no good tutorials on how to check what hardware you have installed on your machine. In Linux there are many ways doing this so it's not an issue but you have to know the needed commands.

I'll start step by step checking different devices on your computer but there is a tool wich shows all so if you don't want to read much just scroll down to the lshw command.

Check on the CPU:

Here is the command that will help you to see what CPU you have installed:

root@Linux ~# cat /proc/cpuinfo

This will print the whole needed information for your CPU. Here is an example:

processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 2
model name : Intel(R) Celeron(R) CPU 2.40GHz
stepping : 9
cpu MHz : 2400.485
cache size : 128 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe up pebs bts cid xtpr
bogomips : 4805.18
clflush size : 64

Checking VGA, LAN and wireless adapters, chipset etc:

root@Linux ~# lspci

Example result:

00:00.0 Host bridge: Intel Corporation 82865G/PE/P DRAM Controller/Host-Hub Interface (rev 02)
00:02.0 VGA compatible controller: Intel Corporation 82865G Integrated Graphics Controller (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev c2)
00:1f.0 ISA bridge: Intel Corporation 82801EB/ER (ICH5/ICH5R) LPC Interface Bridge (rev 02)
00:1f.1 IDE interface: Intel Corporation 82801EB/ER (ICH5/ICH5R) IDE Controller (rev 02)
00:1f.3 SMBus: Intel Corporation 82801EB/ER (ICH5/ICH5R) SMBus Controller (rev 02)
01:0d.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10)

Checking the hard drives:

root@Linux ~# fdisk -l

Example:

isk /dev/hda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x90909090

Device Boot Start End Blocks Id System
/dev/hda1 1 13 104391 83 Linux
/dev/hda2 14 139 1012095 82 Linux swap / Solaris
/dev/hda3 140 9729 77031675 83 Linux

lshw

The easiest way to check all the hardware installed on your box is the lshw command.

Using this command you can see all the hardware. Use the update manager of your distribution to install it if the command line says that the command doesn't exist. The package name is lshw as well.

root@Linux ~# lshw

I won't paste an example for this command since the result is always too huge but it lists everything you need to know.

I hope it was helpful.

How To Check Which Port Is Listening or Open on Linux

How To Check Which Port Is Listening or Open on Linux

For some security reason you may configure SSH or any other protocol using different kind of port number on Linux server. Sometimes it?s important to know which ports are actually listen or open to the system network, it may open for network instruction or hacking.

Basically there are few methods to see which ports are open on Linux.

Option 1:
Check /etc/services file
planetmy:/ # cat /etc/services | grep xxx (xxx = port number)

If the command return no output mean no port configure to listen on the particular port number. For port SSH/22, you should be able to see:
ssh 22/tcp # SSH Remote Login Protocol
ssh 22/udp # SSH Remote Login Protocol

Option 2:
Use netstat command - Print network connections, routing tables, interface statistics, masquerade connections, and multi cast memberships.

planetmy:/ # netstat -nan | grep 22
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 7110/sshd

If the command output return ?LISTEN?, mean the particular port is open or listen on network.

Option 3:
use lsof command - list open files

planetmy:/ # lsof -i -n -P|grep 631
cupsd 17934 lp 0u IPv4 56540196 TCP *:631 (LISTEN)
cupsd 17934 lp 2u IPv4 56540197 UDP *:631

Option 4:
use nmap command - Network exploration tool and security scanner

planetmy:/ # nmap -sS -O 192.168.1.2
Starting nmap 3.50 ( http://www.insecure.org/nmap/ ) at 2008-09-12 10:13 GMT
Interesting ports on 192.168.1.2:
(The 1655 ports scanned but not shown below are in state: closed)
PORT STATE SERVICE
22/tcp open ssh
111/tcp open rpcbind
427/tcp open svrloc
631/tcp open ipp
Device type: general purpose
Running: Linux 2.4.X|2.5.X
OS details: Linux Kernel 2.4.0 - 2.5.20, Linux Kernel 2.4.18 - 2.5.70 (X86)
Nmap run completed ? 1 IP address (1 host up) scanned in 4.146 seconds

The output show the system is running SSH on port 22.

Option 5:
use telnet command - user interface to the TELNET protocol

planetmy:/ # telnet 192.168.1.2 22
Trying 192.168.1.2?
Connected to 192.168.1.2.
Escape character is ?^]?.
SSH-1.99-OpenSSH_4.2

The output show as above mean SSH port 22 is listening on the network

planetmy:/ # telnet 192.168.1.2 122
Trying 192.168.1.2?
telnet: connect to address 192.168.1.2: Connection refused

The output show as above mean port 122 is closed.

Thanks to:
http://www.freecodeclub.com/

Setting Up Your Own Station: A Free Radio Under Linux HowTo

Setting Up Your Own Station: A Free Radio Under Linux HowTo

1. Introduction

So, you want to create your own radio station, don’t you? This manual will help you become a DJ.

2. System Requirements

Minimal requirements for radio broadcasting through your own computer, most of which you are already aware of:

*

150 MHz processor, or better
*

32 MB RAM
*

cable, DSL, or any other kind of broadband internet

and a little free hard disk space for mp3s (which you are going to play).

OS:

*

Some up-to-date Linux distribution, kernel 2.2 or newer.

Software:

*

XMMS 1.2.x http://www.xmms.org/
*

LAME v3.x http://www.sulaco.org/mp3
*

Icecast 1.3.x http://www.icecast.org/
*

Liveice-XMMS. http://star.arm.ac.uk/~spm/software/liveice.html

If using Debian, you can also use:

apt-get install xmms icecast-server

to install xmms and Icecast server. According to LAME, you can use a program called Alien, to convert RPM pack into Debian pack. All you have to do is:

apt-get install alien

and then, as root:

alien package.rpm

to create .deb which you can install, using

dpkg –i

where the name of the Debian package is.

3. Installation

The installation should be rather right-minded. You already should have all packages you need, in order to make things work. If compiling from source, then you should compile and install the software as it is described in its documentation.

If using RedHat, or any of its relative ones you can search for RPM, and download and install it by

rpm –Uvh

where the name of the RPM, which you use is.

If using Debian, just write

apt-get install xmms

icecast-server

to install xmms and Icecast server. According to LAME, you can use a program called Alien, to convert RPM package into Debian package. Install it:

apt-get install alien

then you can use it as root:

alien package.rpm

and the packages can be installed by using

dpkg –i

followed by the package’s name. For example:

dpkg -i .deb

And don’t forget that you should be root to do most of the above. And now, after the installation of all programs you need we have to set them in order to work properly.

4. Configuration

First of all we should configure the Icecast server. Find the directory which contains the Icecast server configuration files (in my case it was /etc/icecast, and I suppose it’s the same if installed by RPM; if you compiled the program on your own, then you are prepared well enough to know where the settings should be) and there you should have many “.dist”-files. Now rename all that files by deleting the “.dist” part. For example if the file name is “icecast.conf.dist” the new one should be “icecast.conf”. If there are no more “.dist”-files then you are doing well.

Now open icecast.conf with your favorite editor. The configuration is rather right-minded and simple, but anyway I’ll guide you through it. Near the beginning of the file you’ll find location/information fields:

location Just west of Mars

rp_email kirk@enterprise.space

server_url http://www.icecast.org/

fill them with the information, that you want people to see, when visiting your web-radio-station.

The next section you have to look at is the one for the server limit:

max_clients 900

max_clients_per_source 900

max_sources 10

max_admins 5

throttle 10.0

For most of the users this is much more than enough. Just set the parameters according to the speed of your Internet connection. Probably you’ll prefer

max_clients

and

max_clients_per_source

to be set at 10, and the rest you can leave the way it is. Now go down the file while you reach:

encoder_password hackme

admin_password hackme

oper_password hackme

If installed the Icecast server under Debian, or support of encrypted passwords enabled, you should crypt the password in this file using program, called mkpasswd (which probably you already have installed on your system). To do this use:

mkpasswd --crypt

Then copy and paste the result in the file. It should look like this:

encoder_passwd --WZKu0fXj3bQ

admin_passwd --WZKu0fXj3bQ

oper_passwd --WZKu0fXj3bQ

No matter which way of installation you made, you should change the password into something else than “hackme”. In the common case the three passwords should be the same. Remember the password you use, because you will use it latter during the configuration of the Liveice-XMMS.

Go down the file again and find:

console_mode 0

change the value at 3, that way the loading will be in text mode.

Usually you don’t have to change the rest of the configuration file. The advanced users can look through the rest of the settings.

Now, let’s configure the Liveice-XMMS:

Restart the XMMS, in order to make it possible to notice that there is another plugin. Make right click on the XMMS and choose Preferences. Go to Effect/General Plugins. In the list under Effect Plugins you should find Liveince. In case you can’t find it check out the Liveice-XMMS installation. After choosing Liveince, click on Configure.

Most of these audio format settings are standard, so you won’t have to change them much. Change the “Encoder type” to ‘Lame’, and the “executable name” to ‘Lame’. If already have any version of Lame on your machine, then set the path to it. Under “Description” you can consider the exact changes by yourself.

Go to Server and change the “Encoder Password” into the one that’s written in the Icecast configuration (and I told you to remember). You shouldn't type the password in encrypted mode if you have encrypted it.

Now everything is set and ready. Click OK. Check “Use Plugins” in the dialog “Preferences”, which should still be in front of you, and click OK again.

In terminal window type ‘icecast’ and press Enter. You should see how it’s getting started and proceeds into text mode.

If you are listening to a song, stop it and play it again.

Nothing went wrong…? There wasn’t big BANG!!! I hope so!

Ask a friend to connect to your IP through XMMS or any other mp3-player at http://yourcomputer:8000 … there should be music playing! If this is not happening, check out the FAQ to solve the problem.

If everything is OK, congratulations – you are now a DJ!

5. FAQ

Make sure that Icecast works. If the problems are still there, go to the conf file, at the place where you changed console_mode to 3, and change it back to 0 (that way you can receive some debug messages). You should be connecting as source, other ways check the Liveice settings. If you are connected as ‘source’, or as ‘encoder’, and your friend is trying to connect, but you don’t receive a message for this, then the problem is not in you!

Linux advanced commands

Linux advanced commands

Command		Description
	apropos whatis	Show commands pertinent to string. See also threadsafe
	man -t man | ps2pdf - > man.pdf	make a pdf of a manual page
	which command	Show full path name of command
	time command	See how long a command takes
	time cat	Start stopwatch. Ctrl-d to stop. See also sw
	nice info	Run a low priority command (The "info" reader in this case)
	renice 19 -p $$	Make shell (script) low priority. Use for non interactive tasks
dir navigation
	cd -	Go to previous directory
	cd	Go to $HOME directory
	(cd dir && command)	Go to dir, execute command and return to current dir
	pushd .	Put current dir on stack so you can popd back to it
file searching
	alias l='ls -l --color=auto'	quick dir listing
	ls -lrt	List files by date. See also newest and find_mm_yyyy
	ls /usr/bin | pr -T9 -W$COLUMNS	Print in 9 columns to width of terminal
	find -name '*.[ch]' | xargs grep -E 'expr'	Search 'expr' in this dir and below. See also findrepo
	find -type f -print0 | xargs -r0 grep -F 'example'	Search all regular files for 'example' in this dir and below
	find -maxdepth 1 -type f | xargs grep -F 'example'	Search all regular files for 'example' in this dir
	find -maxdepth 1 -type d | while read dir; do echo $dir; echo cmd2; done	Process each item with multiple commands (in while loop)
	find -type f ! -perm -444	Find files not readable by all (useful for web site)
	find -type d ! -perm -111	Find dirs not accessible by all (useful for web site)
	locate -r 'file[^/]*\.txt'	Search cached index for names. This re is like glob *file*.txt
	look reference	Quickly search (sorted) dictionary for prefix
	grep --color reference /usr/share/dict/words	Highlight occurances of regular expression in dictionary
archives and compression
	gpg -c file	Encrypt file
	gpg file.gpg	Decrypt file
	tar -c dir/ | bzip2 > dir.tar.bz2	Make compressed archive of dir/
	bzip2 -dc dir.tar.bz2 | tar -x	Extract archive (use gzip instead of bzip2 for tar.gz files)
	tar -c dir/ | gzip | gpg -c | ssh user@remote 'dd of=dir.tar.gz.gpg'	Make encrypted archive of dir/ on remote machine
	find dir/ -name '*.txt' | tar -c --files-from=- | bzip2 > dir_txt.tar.bz2	Make archive of subset of dir/ and below
	find dir/ -name '*.txt' | xargs cp -a --target-directory=dir_txt/ --parents	Make copy of subset of dir/ and below
	( tar -c /dir/to/copy ) | ( cd /where/to/ && tar -x -p )	Copy (with permissions) copy/ dir to /where/to/ dir
	( cd /dir/to/copy && tar -c . ) | ( cd /where/to/ && tar -x -p )	Copy (with permissions) contents of copy/ dir to /where/to/
	( tar -c /dir/to/copy ) | ssh -C user@remote 'cd /where/to/ && tar -x -p'	Copy (with permissions) copy/ dir to remote:/where/to/ dir
	dd bs=1M if=/dev/sda | gzip | ssh user@remote 'dd of=sda.gz'	Backup harddisk to remote machine
rsync (Use the --dry-run option for testing)
	rsync -P rsync://rsync.server.com/path/to/file file	Only get diffs. Do multiple times for troublesome downloads
	rsync --bwlimit=1000 fromfile tofile	Locally copy with rate limit. It's like nice for I/O
	rsync -az -e ssh --delete ~/public_html/ remote.com:'~/public_html'	Mirror web site (using compression and encryption)
	rsync -auz -e ssh remote:/dir/ . && rsync -auz -e ssh . remote:/dir/	Synchronize current directory with remote one
ssh (Secure SHell)
	ssh $USER@$HOST command	Run command on $HOST as $USER (default command=shell)
	ssh -f -Y $USER@$HOSTNAME xeyes	Run GUI command on $HOSTNAME as $USER
	scp -p -r $USER@$HOST: file dir/	Copy with permissions to $USER's home directory on $HOST
	ssh -g -L 8080:localhost:80 root@$HOST	Forward connections to $HOSTNAME:8080 out to $HOST:80
	ssh -R 1434:imap:143 root@$HOST	Forward connections from $HOST:1434 in to imap:143
wget (multi purpose download tool)
	(cd cmdline && wget -nd -pHEKk http://www.pixelbeat.org/cmdline.html)	Store local browsable version of a page to the current dir
	wget -c http://www.example.com/large.file	Continue downloading a partially downloaded file
	wget -r -nd -np -l1 -A '*.jpg' http://www.example.com/dir/	Download a set of files to the current directory
	wget ftp://remote/file[1-9].iso/	FTP supports globbing directly
	wget -q -O- http://www.pixelbeat.org/timeline.html | grep 'a href' | head	Process output directly
	echo 'wget url' | at 01:00	Download url at 1AM to current dir
	wget --limit-rate=20k url	Do a low priority download (limit to 20KB/s in this case)
	wget -nv --spider --force-html -i bookmarks.html	Check links in a file
	wget --mirror http://www.example.com/	Efficiently update a local copy of a site (handy from cron)
networking (Note ifconfig, route, mii-tool, nslookup commands are obsolete)
	ethtool eth0	Show status of ethernet interface eth0
	ethtool --change eth0 autoneg off speed 100 duplex full	Manually set ethernet interface speed
	iwconfig eth1	Show status of wireless interface eth1
	iwconfig eth1 rate 1Mb/s fixed	Manually set wireless interface speed
	iwlist scan	List wireless networks in range
	ip link show	List network interfaces
	ip link set dev eth0 name wan	Rename interface eth0 to wan
	ip link set dev eth0 up	Bring interface eth0 up (or down)
	ip addr show	List addresses for interfaces
	ip addr add 1.2.3.4/24 brd + dev eth0	Add (or del) ip and mask (255.255.255.0)
	ip route show	List routing table
	ip route add default via 1.2.3.254	Set default gateway to 1.2.3.254
	tc qdisc add dev lo root handle 1:0 netem delay 20msec	Add 20ms latency to loopback device (for testing)
	tc qdisc del dev lo root	Remove latency added above
	host pixelbeat.org	Lookup DNS ip address for name or vice versa
	hostname -i	Lookup local ip address (equivalent to host `hostname`)
	whois pixelbeat.org	Lookup whois info for hostname or ip address
	netstat -tupl	List internet services on a system
	netstat -tup	List active connections to/from system
windows networking (Note samba is the package that provides all this windows specific networking support)
	smbtree	Find windows machines. See also findsmb
	nmblookup -A 1.2.3.4	Find the windows (netbios) name associated with ip address
	smbclient -L windows_box	List shares on windows machine or samba server
	mount -t smbfs -o fmask=666,guest //windows_box/share /mnt/share	Mount a windows share
	echo 'message' | smbclient -M windows_box	Send popup to windows machine (off by default in XP sp2)
text manipulation (Note sed uses stdin and stdout, so if you want to edit files, append newfile)
	sed 's/string1/string2/g'	Replace string1 with string2
	sed 's/\(.*\)1/\12/g'	Modify anystring1 to anystring2
	sed '/ *#/d; /^ *$/d'	Remove comments and blank lines
	sed ':a; /\\$/N; s/\\\n//; ta'	Concatenate lines with trailing \
	sed 's/[ \t]*$//'	Remove trailing spaces from lines
	sed 's/\([\\`\\"$\\\\]\)/\\\1/g'	Escape shell metacharacters active within double quotes
	seq 10 | sed "s/^/ /; s/ *\(.\{7,\}\)/\1/"	Right align numbers
	sed -n '1000p;1000q'	Print 1000th line
	sed -n '10,20p;20q'	Print lines 10 to 20
	sed -n 's/.*