MOHAMMED AL-RUDAINI

Certificate of Completion in Hadoop 101

2018-01-10T00:40:00.001+00:00

Certificate of Completion in Hadoop 101

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Badge link.

Certificate of Completion in Big Data 101

2018-01-10T00:28:00.000+00:00

Certificate of Completion in Big Data 101

Cirtificate link.

Badge link.

Index-Based Join in MapReduce Using Hadoop MapFiles

2017-03-10T20:11:00.002+00:00

Full Article text here → Index-Based Join in MapReduce Using Hadoop MapFiles

N-Queens Problem Solving Using Linear Programming in GNU Linear Programming Kit (GLPK)

2017-03-10T20:05:00.002+00:00

Full Report with code here →N-Queens Problem Solving Using Linear Programming in GNU Linear Programming Kit (GLPK)

N-Queens Problem Solving Using Genetic Algorithm in HeuristicLab.

2017-03-10T20:01:00.001+00:00

Full Report with code here →N-Queens Problem Solving Using Genetic Algorithm in HeuristicLab.

JADE Based Camera Surveillance Multi-Agent System

2017-03-10T19:22:00.003+00:00

Full Report with code here → JADE Based Camera Surveillance Multi-Agent System

8 Tiles Puzzle Solving Using IDS, and A* Search.

2017-03-10T13:56:00.001+00:00

**Full Report with code here → 8 Tiles Puzzle Solving Using IDS, and A* Search.**

Speed of light, time and space (wide view study):

2012-06-30T19:06:00.000+01:00

Speed of light is one of the most things I read about, I know that I am not a physician but I got my logic, regarding logic as the base of all sciences, so what is speed of light in my point of view.

At first think of yourself on a road of two ends, and you was standing at one end, then you run three times faster than the speed of light, arrive to the second end of the road and turn back, logically what you will see?, just think of it.

What will happen in my idea is that the person when he or she turn back will see himself coming along the way, this will be the picture or the view of him coming, the idea is that he or she was faster than his or her picture, so he or she changes his level of time.

Scientist has approved that as a thing reaches the speed of light it will have a time delay but if it reaches the speed of light its delay in time will be an infinite value so we can think of it as its time has stopped.

But if that thing accelerate more than the speed of light the delay will come back from infinity down to zero delay but in an imaginary value, so they take it as unsupported value as it out of physics laws but this value has its own dimension as we know that imaginary value is the third dimension.

Someone will ask me is he or she travels to the future or the past, but what is the future or the past for you related to what level of time, so if the basic level of time was that the person start his running in, this person will be traveled to the future as he sees what will happen to him, if the level of time for you is when the person stops and turn back, this person will be traveled to the past as he sees what happened to him, so what is the base of time, future is like past. Wooooooow.

Is it crazy huh. Wait. Think of another thing using the same example, “space”, the person who ran along that way seems to be go along the same space, but if we think again the space around him has changed, how is that?, how he is in a place in the same time seeing himself coming from another place, someone will say he just sees a picture of him coming, that’s true but think closely if time shifted to a new dimension is not in the same dimension so he is in another dimension of space too, but still can see himself in another space dimension, but not the opposite, because the running one can't see himself in the finish end waiting, as we all don't know what we will happen to us in the future.

Dimensions are like spheres one inside the other and parallel to each other at the same time, a law in one dimension will be applicable in the interior dimension but not in the exterior dimension, so each dimension has its own limitation of knowledge, but the outermost one will hold all the knowledge of all sciences.

Every dimension units like length, weight, speed, and time vary from the same units in other dimensions, and also has its own characteristics, so it has its own laws too.

So what will happened if dimensions are not parallel and interfere with each other, in one sentence I will say what will happened is a collection of miracles.

I will talk another time in that so let’s get back to our discussion, how can we accelerate thing to be faster than light.

So the delay in time will be true but out of our dimension, but there is a problem in speed, any mass in our life get more weight as it accelerate faster, and so need more power to handle that bigger weight to accelerate faster, and so there will be a great amount of power to make this thing happened.

But even mass is a type of energy, and to make anything travel closely or faster than light it should be of mass as near or smaller than the mass of an electron for example or has no mass at all, this is the way to do if we can change mass into a new type of energy that can move but has no mass.

What things that has no mass? Even light has a mass as small as just being the fastest thing, but still there is one more, energy the pure one has no or relatively zero mass and this makes us thinking of the string theory of energy, wish considering the smallest part of life is within a strings of energy that makes all known things in our universe.

So if we can decompose anything from its real matter to its real energy strings, we can then accelerate it more times faster than light.

The most important thing here is if strings of energy are real and I think that so, strings still have its own imaginary or dimensional physics as it out of time consideration and space free too, in other words it doesn't belong to a specific dimension, it is multidimensional, and goes from one shape to one another inside the same dimension and also between dimensions, so I can't tell how can we control it.

Energy has its own butterfly effect too, small amount of it in some place and time in a dimension can cause another effect in another space and time may be in the same or another dimension too.

Dell OptiPlex 330 Diagnostic "Error" Lights:

2012-06-26T01:39:00.000+01:00

Dell OptiPlex 330 Diagnostic "Error" Lights:

Many Dell OptiPlex models have diagnostic or error lights in the front or the back panels, the idea of that lights is to help to identify the state of the PC components, so here we will talk about these lights states and how we can fix them.

The lights are like binary 0 and 1, or in our case off and on, in this model we have 11 Light States, each state has its own meaning "Problem", this states works only in the time of booting so when the system finish booting with no problem all the lights goes off.

Problem:

The computer is in a normal "off" condition, or a possible pre-BIOS failure has occurred.

Note: The diagnostic lights are not lit after the computer successfully boots to the operating system.

Solution:

Plug the computer into a working electrical outlet and press the power button.

Problem:

A possible BIOS failure has occurred; the computer is in the recovery mode.

Solution:

Run the BIOS Recovery utility, wait for recovery completion, and then restart the computer.

Problem:

A possible processor failure has occurred.

Solution:

Reinstall the processor and restart the computer

Problem:

Memory modules are detected, but a memory failure has occurred.

Solution:

· If you have one memory module installed, reinstall it and restart the computer.

· If you have two or more memory modules installed, remove the modules, reinstall one module, and then restart the computer. If the computer starts normally, reinstall an additional module. Continue until you have identified a faulty module or reinstalled all modules without error.

· If available, install properly working memory of the same type into your computer.

· If the problem persists, contact Dell Support.

Problem:

A possible graphics card failure has occurred.

Solution:

• If the computer has a graphics card, remove the card, reinstall it, and then restart the computer.

• If the problem still exists, install a graphics card that you know works and restart the computer.

• If the problem persists or the computer has integrated graphics, contact Dell Support.

Problem:

A possible floppy or hard drive failure has occurred.

Solution:

Reseat all power and data cables and restart the computer.

Problem:

A possible USB failure has occurred.

Solution:

Reinstall all USB devices, check cable connections, and then restart the computer.

Problem:

No memory modules are detected.

Solution:

• If you have one memory module installed, reinstall it and restart the computer.

• If you have two or more memory modules installed, remove the modules, reinstall one module, and then restart the computer. If the computer starts normally, reinstall an additional module. Continue until you have identified a faulty module or reinstalled all modules without error.

• If available, install properly working memory of the same type into your computer.

• If the problem persists, contact Dell Support.

Problem:

Memory modules are detected, but a memory configuration or compatibility error exists.

Solution:

• Ensure that no special memory module/memory connector placement requirements exist .

• Verify that the memory modules that you are installing are compatible with your computer.

• If the problem persists, Contact Dell Support.

Problem:

A failure has occurred. This pattern also displays when you enter system setup and may not indicate a problem

Solution:

• Ensure that the cables are properly connected to the system board from the hard drive and the optical drive.

• Check the computer message that appears on your monitor screen.

• If the problem persists, Contact Dell Support.

After POST is complete, all four diagnostic lights turn green briefly before turning off to indicate normal operating condition.

Converting POE incompatible Network device to a POE compatible device.

2012-06-23T23:12:00.001+01:00

How to convert POE incompatible Network device to a POE compatible device:

At first refer to our previous post on how to make a homemade POE Injector.

http://rudaini.blogspot.com/2012/06/home-made-poe-injector.html

Now we will use the Linksys wap54g wireless access point as an example.

As the POE device it means that it is not directly connected to the power adapter, it takes the needed power from the Ethernet cable, but this device is not a POE compatible, we will see the required steps to convert it to a POE compatible device.

First: we use the power adapter to make a POE Injector as the previous post.

Second: we disassemble the Linksys WAP54G Wireless access point, and take out it external circuit.

now take a look to this carefully

What you should do here is to connect the 4^th and 5^th Ethernet pin to the +DC pin through a diode for safety reasons, and connect the 7^th and 8^th Ethernet pins to the –DC pin.

Then connect the P+data Ethernet cable came from your homemade POE injector and the device now is enable to take the power directly from the Ethernet port.

Home Made POE Injector

2012-06-23T18:01:00.003+01:00

Home Made POE Injector:

POE: Power over Ethernet, is a technology used to deliver electrical power to a POE Device over the Ethernet cabling.

the POE Injector used to merge the power signal and the Ethernet signal using one Ethernet cable connected directly connected to the POE device or by using POE enabled switches or routers.

so if you don't have a POE Injector for a POE device and you have only the power adapter for that device and you can't use it because of the distance between the device and the electrical power source, you can use the above diagram to make a POE Injector.

if your network device is a POE compatible, you can connect the POE cable directly into it, and the device itself will handle the demerge of the power and data signals as follows.

but if your device is not a POE compatible you can manually demerge the power signal from the data signal before connecting it to the non-POE compatible device as follows.

or you can convert your non-POE compatible device to a POE compatible device as I will show you in the next post.

Activating Internet Download Manager without any crack

2012-06-22T22:52:00.000+01:00

Activating Internet Download Manager without any crack or patch:

This is how to activate Internet Download Manager with out any crack or patch

First: Download and install any version of the program, then install it on your device.

Second: go to the directory "c:\windows\system32\drivers\etc" and open the file "hosts" using the notepad.

Then add all these lines to the end of the file.

127.0.0.1 tonec.com

127.0.0.1 www.tonec.com

127.0.0.1 registeridm.com

127.0.0.1 www.registeridm.com

127.0.0.1 secure.registeridm.com

127.0.0.1 internetdownloadmanager.com

127.0.0.1 www.internetdownloadmanager.com

127.0.0.1 secure.internetdownloadmanager.com

127.0.0.1 mirror.internetdownloadmanager.com

127.0.0.1 mirror2.internetdownloadmanager.com

127.0.0.1 mirror3.internetdownloadmanager.com

Third: save the file, but if you can't save it in the same folder try to safe it anywhere else like desktop for example naming it "hosts" only with out the extension "hosts.txt", but if you don't see the extension part you can show it from the "view" tab in the "folder options" settings in the control panel, then copy the new file to "c:\windows\system32\drivers\etc" and close the folder.

Finally: open Internet Download Manager Program, then from the Registration Menu click Registration, the Registration window will appear to you, so enter your First Name, Last Name, and Email ind the first three boxes, and in the last box you can use one of these keys.

OP3BQ-I5EAR-UN52H-VR7QX

7TSFG-YWZ5O-YWLSB-89N41

ZJ14C-KHNV1-I9YPK-YITD9

84X1I-3HVW3-MX7ZK-QBG0M

2HM59-AN92L-CP78G-CS668

2CG8P-EO617-EP61F-HS63O

2IM6O-DQ53K-CN57B-HO94X

and enjoy using the program with all its options

USB Flash Disk Fixing Part 1: Components

2011-08-02T01:00:00.003+01:00

We all have some flash disks that is not working, or working with some problems, so at first I should start with flash disk components and their job so when we face the problems we can know which part/s is/are the reason of each problem.

Flash Disk Components:

Male type-A USB connector - provides a physical interface to the host computer.
Crystal oscillator - produces the device's main 12 MHz clock signal and controls the device's data output through a phase-locked loop.
USB mass storage controller - implements the USB host controller. The controller contains a small microcontroller with a small amount of on-chip ROM and RAM.
NAND flash memory chip - stores data. NAND flash is typically also used in digital cameras.
Printed Circuit: is the circuit that connects all the above 4 parts all together.

The typical device may also include:

Jumpers and test pins - for testing during the flash drive's manufacturing or loading code into the microprocessor
LEDs - indicate data transfers or data reads and writes
Write-protect switches - Enable or disable writing of data into memory
Unpopulated space - provides space to include a second memory chip. Having this second space allows the manufacturer to use a single printed circuit board for more than one storage size device
Some drives offer expandable storage via an internal memory card slot, much like a memory card reader.

How the Components of a USB Drive Work

The microcontroller chip of the USB flash drive performs a similar task as a PC's processor, also known as a CPU. Microcontrollers and CPUs perform a very important task in synchronizing Input/Output (I/O) operations, kind of like how your heart works to keep your blood flowing in and out at a pace that is not too fast or too slow for your body at its current state. The memory controller chip is the one that stores data statically, and does not need a battery or anything to maintain the memory inside of it using Floating Gate technology.

Perhaps upon reading the above, you have become a little confused. Well, Floating Gate technology makes the memory controller able to trap electricity (data) and store memory without any extra electricity necessary to be spared for it. Erasing works like this: the voltage is changed which releases the data. These changes in voltage are determined by the computer that you plug your USB flash drive inside of.

The Personal Goal

2011-07-25T00:55:00.003+01:00

The life is not that extended, so anyone can say “I will reach all my goals in it”, in other hand even if my goals still unreachable in my life the best way to feel my satisfaction is to carry it to a level so other interested people can achieve it after my life.

The Idea of Sharing:

Aims for others may be as small as “my goal is something” thus when they reach their ambition they lose themselves cause they don’t realize what is the next stage, or if they don't reach it, their condition will still the same, thus for me the vision is different as “my objective is the most excellence of me” so I will always hunt of the next stage of my objective, and even not that only, I will try joining in others goals.

So my personal target is to but my professional inspiration in the way of others insights and ideas, it’s simple as that many people sharing the same goal is better than one person hiding in his own goals behind the scenes, and in other manner as an individual I have the plan of producing the perfect of me as well as assisting others to dig up the upgrade of themselves too.

The perfect person or the perfect society:

Here is my philosophy in our life which is better? one person seeking his personal goal or one person working with others to attain the public goals, that is because we are not living alone anymore, even the whole society is still linked to the other societies in the world, learning from each others, teaching each others, and helping each others is the perfect alternative for all of humanity all over the world.

The perfect society or the perfect world:

My next idea is the collection of all of my ideas above, one society is still rare of resources even if it is an extensive society, in the modern time the trading, agriculture, technology, Industry, and other evolutionary outlines are associated to each other all around the world, and new ideas are distributing in instant trough all the nations, all societies, and all people.

Conclusion:

Many is better than one, a lot is advanced than many, thus an idea of many is enhanced than an idea of one, and an idea of a lot is improved than an idea of many, hence an idea of the all is the greatest idea ever, for the greatest person, the greatest society, and the greatest globe.

Silent Meditation

2011-07-24T19:31:00.007+01:00

Silent Meditation

For many people the silence is a fuzzy state, this is what they think cause they don’t give it enough envision, that’s because they're not capable of staying in silence for long time, other people think of silence as the part of divine-self of the human like Love, Emotions, Inner lightning, and other concepts, they may be right, but for me the silence is the edge between inner-self and outer-self of our humanity.

What is silence?

Silence is the skill of liberate your outer-self as close to your inner-self so you can release your inner sense as possible to hear in your heart and mind, this also will aid you to attain more space of your outer-self sense, assisting you to earn a better decisions for your life.

Silence as an edge:

The silence outline is not a tiny line between the inner and the outer self, it is a wide space of peace and light between them, this wide field is not empty as others think, it's full of pure feelings that bring you to your self-peace and your inner part of your mind, revealing all of stress and disturbance so you can handle your actions wisely.

Transcendental meditation:

Many people think of transcendental meditation as a religion while it is not, but many religions has a part of its traditions close or related to the transcendental meditation, I'm not very acquainted with other world's religions, but as a Muslim, I know that our prophet Mohammed (peace be upon him) before he was chosen as our prophet and messenger of Islamic religion, he used to go to the cave of Hera’a (a cave near Mecca) to meditate and his first Revelation with the angle (Gabriel) was in it during his meditation, and even thus meditation was not a part of the religion itself but still there as a part of the human best way of getting the pure knowledge of human life and God creations.

Conclusion:
At the end many people still aware of meditation concerning of its similarity to other religions, where the connection between meditation and other religions was it use only, In Islam like an example many people may observe there is several meditation routines used in praying, reading Quran, Hajj, and Omrra, but the usage of meditation is distinct from religion practices.

The most meditation method used in religions practices is silence cause silence of minds still the best way to know the pure elements in humans bodies and souls, so as a Muslim I don’t consider meditation itself as religion-based technique otherwise I can say that most of religions practices are a meditation-based techniques.

SNAPGEAR URL FILTERING

2011-06-09T23:19:00.000+01:00

SNAPGEAR URL FILTERING:

Basic features

1. What filtering application does SnapGear use?

SnapGear offers a version of Secure Computing’s leading Webwasher® URL filtering solution. SnapGear Webwasher filtering uses the same URL database/filtering engine found in the Webwasher enterprise SCM solution. The SnapGear filtering module provides basic filtering functionality that is targeted for smaller businesses. Not all of the Webwasher advanced/enterprise filtering features are included.

2. How does the SnapGear URL filtering module work?

SnapGear administrators create a filtering policy for their organization that resides locally on each SnapGear appliance. SnapGear administrators determine the types of URLs they want to allow or block and create their policy from a set of predetermined categories. The URL filtering engine runs as an Internet service on Webwasher Rating Servers around the world. The SnapGear appliance intercepts HTTP URL requests submitted by internal users and relays them to the Webwasher Rating Server. The Server quickly returns URL category data to the SnapGear appliance which then either blocks or allows user access to the requested Web site according to the local policy.

3. What filtering categories are available with SnapGear?

There are currently more than 60 categories available.

1. Pornography

2. Erotic/Sex

3. Swimwear/Lingerie/Nudity

4. Shopping

5. Auctions/Classified Ads

6. Governmental Organizations

7. Non-Governmental Organizations

8. Cities/Regions/Countries

9. Education

10. Politics

11. Religion

12. Sects

13. Illegal Activities

14. Computer Crime

15. Hate/Discrimination

16. Warez (Illegal Software)

17. Extreme

18. Gambling/Lottery

19. Computer Games

20. Toys

21. Entertainment/Motion Picture

22. Recreation

23. Art/Photography

24. Music/Web Radio

25. Literature

26. Humor/Comic

27. News/Magazines

28. Web Mail

29. Chat/Instant Messaging

30. Newsgroups/Blogs

31. SMS/Ring Tones/Logos

32. Digital Postcards

33. Search Engines/Web Catalogs/Portals

34. Software/Hardware

35. Web Hosting/IT Services

36. Information Security

37. Translation Proxies

38. Anonymous Proxies

39. Illegal Drugs

40. Alcohol

41. Tobacco

42. Self-Help/Addiction/Dependency

43. Dating/Relationships

44. Restaurants/Nutrition

45. Travel

46. Fashion/Beauty

47. Sports

48. Real Estate/Architecture/Residence

49. Nature/Environment

50. Private Homepages

51. Human Resources

52. Shares/Stocks

53. Investment/Insurances

54. Banking/Finances

55. Transportation/Logistics

56. Weapons

57. Health

58. Abortion/Cloning

59. Pharmacy/Drugs

60. Business/Services

61. Promotion/Advertising

62. Spyware

63. Phishing

64. Malicious Web Sites

4. Can I get reports on my Internet traffic, including reports by user?

All of the SnapGear appliances can be purchased with either URL Filtering only or URL Filtering with Reporting. With the reporting option, a pre-defined set of reports provide organizations a better understanding of their Internet traffic. Filtering reports are not run locally. Reports are emailed on a monthly basis to all organizations that subscribe to the reporting service. Your activation certificate will enable access to the reporting option.

Reports include information such as Top 20 sites visited and Top 20 sites blocked. Some reports can be viewed by user IP address or by user name. To report by user name, user authentication is required. This feature is enabled on the firewall Access Control Main Tab. On this tab, Require User Authentication determines if users are asked for a username and password when attempting to access the Internet.

Additionally, SnapGear administrators must select the Identify user by account option in the Content Filtering area of the Webwasher tab.

Note: Internet Explorer users must configure the SnapGear unit as their default Web proxy for password based access to operate correctly.

Additional configuration requirements and options

5. How do I enable Web filtering?

The Web filtering functionality is an add-on module to SnapGear that must be purchased separately. Once purchased, a few simple steps need to be followed to enable filtering. First, navigate to the Webwasher tab of the firewall Access Control configuration area. The Enable Content Filtering checkbox specifies whether Webwasher content filtering will be used or not.

For more detailed information on enabling content filtering, please refer to our Knowledgebase article found at: www.cyberguard.info/snapgear/faqomatic/public_html/fom-serve/cache/468.html

Note: The Content section of the Access Control configuration area refers to a legacy filtering option that cannot be used by new SnapGear customers.

6. How many filtering policies can I create on a single SnapGear appliance?

Only one global Webwasher filtering policy can be assigned per SnapGear appliance. There are many options for customizing this policy to best meet an organizations’ unique need. Additional details are included on this topic in the next section of the FAQ. Business models that require multiple policies and HTTPS or FTP filtering should upgrade to a local Webwasher Server with a complete set of robust Secure Content Management engines including URL Filtering, Anti-Spam, Anti-Virus, SSL Scanning and more.

7. Can I override the Webwasher block/allow policy?

Custom URL and IP Whitelist (allow) and Blacklist (block) entries can be implemented on the SnapGear appliances that override the Webwasher block/allow policy. A number of options are listed below:

· The ACL and Web Lists tabs of the firewall Access Control configuration area allow the SnapGear appliance administrator to override the Webwasher block/allow policy on a site-by-site basis. The ACL section can also be used to exempt specific workstation IPs from the Webwasher Block/Allow policy or to block specific workstation IPs regardless of the Webwasher block/allow policy.

o The Web Lists tab uses URLs or URL fragments to allow (Whitelist) or block (Blacklist) Web sites regardless of the Webwasher block/allow policy. A performance impact is associated with this strategy.

o The ACL tab can use lists of specific IP addresses to allow or block Web sites regardless of the Webwasher block/allow policy. The performance impact associated with this strategy is much lower than when Web Lists are used. This approach requires that each Web site use a stable IP address. Since DNS is not used, when a Websites changes its IP address, it is no longer effectively controlled by the ACL entry. The most common use of this control would be a Whitelist of business partner Extranet sites.

o The ACL tab can also be used to exempt or block specific user workstation IPs from the Webwasher block/allow policy.

§ A user workstation IP address that is exempted from the Webwasher block/allow policy is still restricted by block entries in the Web Lists. A user workstation IP address that is blocked from the Webwasher block/allow policy is still permitted to browse any allow entries in the Web Lists.

o Web List block and allow entries are absolute by default. If a requested URL contains any of the URL fragments defined, a block or allow action will be triggered. Defining overly short URL fragments can result in many sites matching and being allowed or denied erroneously. Secure Computing recommends that URLs be restricted to the shortest length that achieves the desired result.

· Every SnapGear appliance can accommodate several hundred override/exempt entries in a combined total for the ACL and Web Lists. The performance impact and the number of entries vary significantly with the length of the Web List URLs and the general load upon the appliance. The ACL IP format supports longer lists but Secure Computing recommends that the number of entries should not exceed 200 if slow Web page delivery is to be avoided. If override/exempt requirements are in excess of 200 entries, the customer should consider implementing a stand-alone Webwasher URL filter application.

8. If a site is not rated by Webwasher, can it still be blocked?

SnapGear administrators can determine if they want all sites not yet rated by Webwasher to be allowed or blocked.

9. What if access to the Webwasher Rating Server is unavailable – will the appliance continue to filter Web access?

The Cache option in the SnapGear appliance enables the caching of content rating results. It allows continued Web filtering operation with the cached rating results in the event that access to the Webwasher Rating Servers is unavailable. The Cache option on the SnapGear appliance will also improve performance and will require approximately 2 megabytes of memory.

Working With DHCP Server In Linux

2011-05-22T02:53:00.001+01:00

Introduction

Normally if you have a cable modem or DSL, you get your home PC's IP address dynamically assigned from your service provider. If you install a home cable/DSL router between your modem and home network, your PC will most likely get its IP address at boot time from the home router instead. You can choose to disable the DHCP server feature on your home router and set up a Linux box as the DHCP server.

Download and Install the DHCP Package

Most RedHat and Fedora Linux software product packages are available in the RPM format, whereas Debian and Ubuntu Linux use DEB format installation files. When searching for these packages, remember that the filename usually starts with the software package name and is followed by a version number, as in dhcp-3.23.58-4.i386.rpm.

Note: With Fedora / Redhat the package to install would be dhcp. With Debian / Ubuntu the package is dhcp3-server.

Starting the DHCP Server

The methodologies vary depending on the variant of Linux you are using as you’ll see next.

Note: Make sure you configure your server before starting!

Fedora / CentOS / RedHat

With these flavors of Linux you can use the chkconfig command to get dhcpd configured to start at boot:

[root@bigboy tmp]# chkconfig dhcpd on

To start, stop, and restart dhcpd after booting use the service command:

[root@bigboy tmp]# service dhcpd start

[root@bigboy tmp]# service dhcpd stop

[root@bigboy tmp]# service dhcpd restart

To determine whether dhcpd is running you can issue either of these two commands. The first will give a status message. The second will return the process ID numbers of the dhcpd daemons.

[root@bigboy tmp]# service dhcpd status

[root@bigboy tmp]# pgrep dhcpd

Note: Remember to run the chkconfig command at least once to ensure dhcpd starts automatically on your next reboot.

Ubuntu / Debian

With these flavors of Linux the commands are different. Try installing the sysv-rc-conf and sysvinit-utils DEB packages as they provide commands that simplify the process. For help on downloading and installing the packages, see Chapter 6, "Installing Linux Software".) You can use the sysv-rc-conf command to get dhcp3-server configured to start at boot:

user@ubuntu:~$ sudo sysv-rc-conf dhcp3-server on

To start, stop, and restart dhcpd after booting the service command is the same:

user@ubuntu:~$ sudo service dhcp3-server start

user@ubuntu:~$ sudo service dhcp3-server stop

user@ubuntu:~$ sudo service dhcp3-server restart

To determine whether dhcpd is running you can issue either of these two commands. The first will give a status message. The second will return the process ID numbers of the dhcpd daemons.

user@ubuntu:~$ sudo service dhcp3-server status

user@ubuntu:~$ pgrep dhcp

Note: Remember to run the sysv-rc-conf command at least once to ensure mysql starts automatically on your next reboot.

dhcpd.conf File

You can define your server configuration parameters in the dhcpd.conf file which may be located in the /etc the /etc/dhcpd or /etc/dhcp3 directories depending on your version of Linux.

Note: The skeleton dhcp.conf file that is created when you install the package may vary in its completeness. In Ubuntu / Debian, the skeleton dhcpd.conf file is extensive with most of the commands deactivated with a # sign at the beginning. In Fedora / RedHat / CentOS an extensive sample is also created with activated commands. It is found in the following location which you can always use as a guide.

/usr/share/doc/dhcp*/dhcpd.conf.sample

Note: The dhcpd.conf configuration file formats in Debian / Ubuntu and Redhat / Fedora are identical.

Here is a quick explanation of the dhcpd.conf file: Most importantly, there must be a subnet section for each interface on your Linux box.

ddns-update-style interim

ignore client-updates

subnet 192.168.1.0 netmask 255.255.255.0 {

# The range of IP addresses the server

# will issue to DHCP enabled PC clients

# booting up on the network

range 192.168.1.201 192.168.1.220;

# Set the amount of time in seconds that

# a client may keep the IP address

default-lease-time 86400;

max-lease-time 86400;

# Set the default gateway to be used by

# the PC clients

option routers 192.168.1.1;

# Don't forward DHCP requests from this

# NIC interface to any other NIC

# interfaces

option ip-forwarding off;

# Set the broadcast address and subnet mask

# to be used by the DHCP clients

option broadcast-address 192.168.1.255;

option subnet-mask 255.255.255.0;

# Set the NTP server to be used by the

# DHCP clients

option ntp-servers 192.168.1.100;

# Set the DNS server to be used by the

# DHCP clients

option domain-name-servers 192.168.1.100;

# If you specify a WINS server for your Windows clients,

# you need to include the following option in the dhcpd.conf file:

option netbios-name-servers 192.168.1.100;

# You can also assign specific

# ethernet MAC address as follows (Host's name is "laser-printer":

host laser-printer {

hardware ethernet 08:00:2b:4c:59:23;

fixed-address 192.168.1.222;

}

# List an unused interface here

subnet 192.168.2.0 netmask 255.255.255.0 {

}

There are many more options statements you can use to configure DHCP. These include telling the DHCP clients where to go for services such as finger and IRC. Check the dhcp-options man page after you do your install:

[root@bigboy tmp]# man dhcp-options

Note: The host statement seen in the sample dhcpd.conf file can be very useful. Some devices such as network printers default to getting their IP addresses using DHCP, but users need to access them by a fixed IP address to print their documents. This statement can be used to always provide specific IP address to DHCP queries from a predefined a NIC MAC address. This can help to reduce systems administration overhead.

DHCP Servers with Multiple NICs

DHCP servers with multiple interfaces pose two configuration challenges. The first is setting up the correct routing and the second is making sure only the required interfaces are listening to serve DHCP. Don’t worry, both will be discussed next.

Routing

When a DHCP configured PC boots, it requests its IP address from the DHCP server. It does this by sending a standardized DHCP broadcast request packet to the DHCP server with a source IP address of 255.255.255.255.

If your DHCP server has more than one interface, you have to add a route for this 255.255.255.255 address so that it knows the interface on which to send the reply; if not, it sends it to the default gateway. (In both of the next two examples, we assume that DHCP requests will be coming in on interface eth0).

Note: You can't run your DHCP sever on multiple interfaces because you can only have one route to network 255.255.255.255. If you try to do it, you'll discover that DHCP serving working on only one interface.

Temporary Solution

You can temporarily add a route to 255.255.255.255 using the route add command as seen below.

[root@bigboy tmp]# route add -host 255.255.255.255 dev eth0

If you want this routing state to be maintained after a reboot, then use the permanent solution that's discussed next.

Permanent Solution

Create a permanent route to 255.255.255.255. This will vary according to your version of Linux

Fedora / RedHat / CentOS: Add the route to your /etc/sysconfig/network-scripts/route-eth0 file if the route needs to be added to your eth0 interface.

# File /etc/sysconfig/network-scripts/route-eth0

255.255.255.255/32 dev eth0

Ubuntu / Debian: Add the route to your /etc/network/interfaces file. In this case the route is added to the eth0 interface.

# File: /etc/network/interfaces

iface eth0 inet static

up route add -host 255.255.255.255 eth0

Listening

Once you have defined the interface for your DHCP routing you should also ensure that your DHCP server only listens on that interface and no others. This methodology to do this varies depending on your versión of Linux.

Fedora / RedHat / CentOS: The /etc/sysconfig/dhcpd file must be edited and the DHCPDARGS variable edited to include the preferred interface. In this example interface eth0 is preferred.

# File: /etc/sysconfig/dhcpd

DHCPDARGS=eth1

Debian / Ubuntu: The /etc/default/dhcp3-server file must be edited and the INTERFACES variable edited to include the preferred interface. In this example interface eth0 is preferred.

# File: /etc/default/dhcp3-server

INTERFACES="eth0"

You will be able to verify success in one of two ways. First the netstat command using the –au options will give the list of interfaces listening on the bootp (DHCP) UDP port.

[root@bigboy-f ~]# netstat -au | grep bootp

udp 0 0 192.168.1.100:bootps *:*

[root@bigboy-f ~]#

Secondly, your /var/log/messages file will also reveal the defined interfaces used when the DHCPd daemon was restarted.

Jan 8 17:22:44 bigboy dhcpd: Listening on LPF/eth0/00:e0:18:5c:d8:41/192.168.1.0/24

Jan 8 17:22:44 bigboy dhcpd: Sending on LPF/eth0/00:e0:18:5c:d8:41/192.168.1.0/24

Success! You can go back to lunch!

Using a Single DHCP Server to Serve Multiple Networks

As stated before, DHCP clients send their requests for IP addresses to a broadcast address which is limited to the local LAN. This would imply that a DHCP server is required on each subnet. Not so. It is possible to configure routers to forward DHCP requests to a DHCP server many hops away. This is done by inserting the IP address of the router's interface on the DHCP client's network into the forwarded packet. To the DHCP server, the non-blank router IP address field takes precedence over the broadcast address and it uses this value to provide a DHCP address that is meaningful to the client. The DHCP server replies with a broadcast packet, and the router, which has kept track of the initial forwarded request, forwards it back towards the client. You can configure this feature on Cisco devices by using the ip helper-address command on all the interfaces on which DHCP clients reside. Here is a configuration sample that points to a DHCP server with the IP address 192.168.36.25:

interface FastEthernet 2/1

ip address 192.168.1.30 255.255.255.0

ip helper-address 192.168.36.25

Simple DHCP Troubleshooting

The most common problems with DHCP usually aren't related to the server; after the server is configured correctly there is no need to change any settings and it therefore runs reliably. The problems usually occur at the DHCP client's end for a variety of reasons. The following sections present simple troubleshooting steps that you can go through to ensure that DHCP is working correctly on your network.

DHCP Clients Obtaining 169.254.0.0 Addresses

Whenever Microsoft DHCP clients are unable to contact their DHCP server they default to selecting their own IP address from the 169.254.0.0 network until the DHCP server becomes available again. This is frequently referred to as Automatic Private IP Addressing (APIPA). Here are some steps you can go through to resolve the problem:

Ensure that your DHCP server is configured correctly and use the pgrep command discussed earlier to make sure the DHCP process is running. Pay special attention to your 255.255.255.255 route, especially if your DHCP server has multiple interfaces.
Give your DHCP client a static IP address from the same range that the DHCP server is supposed to provide. See whether you can ping the DHCP server. If you cannot, double-check your cabling and your NIC cards.
DHCP uses the BOOTP protocol for its communication between the client and server. Make sure there are no firewalls blocking this traffic. DHCP servers expect requests on UDP port 67 and the DHCP clients expect responses on UDP port 68. Use tcpdump on the server's NIC to verify the correct traffic flows.

Other DHCP Failures

If the DHCP server fails to start then use your regular troubleshooting techniques to help rectify your problems. Most problems with an initial setup are often due to:

Incorrect settings in the /etc/dhcpd.conf file such as not defining the networks for which the DHCP server is responsible;
Firewall rules that block the DHCP bootp protocol on UDP ports 67 and 68;
Routers failing to forward the bootp packets to the DHCP server when the clients reside on a separate network.

Always check your /var/logs/messages file for dhcpd errors and remember that mandatory keywords in your configuration file may change when you upgrade your operating system. Always read the release notes to be sure.

RAID part 3 RAID Level 1.

2009-11-06T22:04:00.000+00:00

RAID Level 1

RAID level 1 is known as disk mirroring. Disk mirroring uses two or more hard drives and duplicates the data from one drive to the others. The fact that RAID 1 does store a second copy of the data on another member of the volume means that this solution does offer fault tolerance. Fault tolerance is the concept that if one part of the solution fails, the other guy will pick up the workload and the solution will continue to function. If one of the disks in the mirror fails, you can replace the failed disk by breaking the mirror, adding a new functioning disk, and then rebuilding the mirror from the existing disk that did not fail. Once you have reestablished the mirror, you have your fault tolerance back.

The figure below displays the concept of a mirror volume. When a user saves data to a mirrored volume, the data is written to all disks that make up the volume.

RAID level 1 (Mirror) concept.

Creating a Mirrored Volume in Windows Server

In this step-by-step you will create a mirrored volume on a Windows server using two of the dynamic disks created in the preceding walkthrough. Remember that a mirrored volume stores all the data on both members (disks) in the volume. To create a mirrored volume, follow these steps:

1. Right-click My Computer and choose Manage.

2. Right-click an area of unallocated space on disk 1 and choose Create Volume.

3. The Create Volume Wizard appears. Click Next.

4. Choose the volume type of Mirrored Volume, which is the volume type you wish to create, and choose Next.

5. Choose two or more disks as a selected disk for the mirrored volume and type 200 Mb as the total amount of space used on each disk. Also notice that the total space used by the volume is 200Mb as well. Although there is 200MB per disk, you can store only 200Mb the other 200MB is to store a copy of the data in case of disaster.

6. Click Next.

7. Assign drive Y as the drive letter and choose Next.

8. Choose Next to format for NTFS and other settings.

9. Choose Finish. The mirrored volume is created. Notice that the legend in disk management displays the color codes for each volume type.

RAID 1 using hardware controllers:
RAID 1 is known as disk mirroring whereby the data is duplicated across two different disks but using only one disk controller. When using two disk controllers, one with each a hard disk connected to it, we term the RAID 1 solution disk duplexing rather than disk mirroring.

RAID part 2 RAID Level 0.

2009-11-06T01:30:00.003+00:00

RAID Level 0:

RAID level 0 is called striping or striped volumes. With RAID 0 multiple disks are used to create a volume; when data is saved to the volume, the data is split up and spread across all disks in the volume. The benefit of striped volumes is that all disks are written to at the same time, giving you a performance benefit. For example, if you are saving a 12MB file to drive D and drive D is a striped volume made up of four disks, we can generalize the save operation by saying that each disk will save 3MB of data each and all disks will work at the same time to do the save operation that totals 12MB. If you only had one disk working for that 12MB save operation, it would take four times longer.

RAID 0 "Striped set without parity" or "Striping". Provides improved performance and additional storage but no redundancy or fault tolerance. Because there is no redundancy, this level is not actually a Redundant Array of Inexpensive Disks, i.e. not true RAID. However, because of the similarities to RAID (especially the need for a controller to distribute data across multiple disks), simple stripe sets are normally referred to as RAID 0. Any disk failure destroys the array, which has greater consequences with more disks in the array (at a minimum, catastrophic data loss is twice as severe compared to single drives without RAID). A single disk failure destroys the entire array because when data is written to a RAID 0 drive, the data is broken into fragments. The number of fragments is dictated by the number of disks in the array. The fragments are written to their respective disks simultaneously on the same sector. This allows smaller sections of the entire chunk of data to be read off the drive in parallel, increasing bandwidth. RAID 0 does not implement error checking so any error is unrecoverable. More disks in the array means higher bandwidth, but greater risk of data loss.RAID 0 is strictly for the performance benefit in the read and write operations.

RAID level 0 concept.

Configuring RAID 0 on a Windows Server
Windows Server offers a software RAID feature, which means that the operating system is responsible for the creation and management of the RAID volume. A hardware RAID solution would offer a better-performing solution, but it would be more expensive.

Before you can start creating fault-tolerant volumes, you must be sure to upgrade your disk to a dynamic disk. Dynamic disk is the disk type used in Windows to create RAID volumes. Take the following steps to convert your disk from a basic disk (which does not support volumes) to a dynamic disk and then create a RAID 0 volume.

1. Right-click My Computer and choose Manage.

2. In the Computer Management console, select Disk Management on the left-hand side.

3. Right-click your disk on the right side and choose Upgrade To Dynamic Disk.

4. The Upgrade To Dynamic Disk dialog box appears, asking you to select which disk you want to make dynamic. Select all disks that you wish to convert to dynamic disk.

5. Click OK.

6. Click Convert.

7. Click Yes.

8. Click Yes again.

9. Click OK. You will need to reboot the system.

10. After the system has rebooted, log on as an administrative account, choose No to restarting again, and then start Disk Management.

11. Right-click an area of unallocated space on disk 1 and choose Create Volume.

12. The Create Volume Wizard appears. Click Next.

13. Choose the volume type of Striped Volume, which is the volume type you want to create, and choose Next.

14. You will now need to choose the disks that will participate in the striped volume solution. Select disks you want from the left side and click Add to add to the striped volume. Notice that the disk you started the volume on was already selected as a member of the volume.

15. Once you have added each disk, at the bottom of the dialog box type the amount of space you want to use on each disk for the volume. Type 200 and notice that each disk will use 200MB—for a total of 600MB for the entire volume.

16. Click Next.

17. Assign a drive letter like Z for the striped drive.

18. Click Next.

19. Click Next to format for NTFS and other settings.

20. Click Finish and the new Striped Volume will be created. Notice that drive S shows multiple times because it is made up of multiple disks.

21. Close all windows.

RAID part 1 Introduction.

2009-11-05T23:42:00.001+00:00

Introduction:

A Redundant Array of Independent Disks (RAID) controller is a piece of hardware or system software that control and manage the RAID level of the RAID storage, it is largely used in servers because they have a large space of storage that importantly be recoverable and secure.

The RAID controller is also largely used in clustered environments like Network-attached storage (NAS), which are standalone devices, usually SCSI, that have a network interface but no PC. NAS is possibly include a built-in RAID controller to allow all the hard disks to be fault tolerant and function as a single volume.

RAID combines two or more physical hard disks into a single logical unit by using either special hardware or software. Hardware solutions often are designed to present themselves to the attached system as a single hard drive, so that the operating system would be unaware of the technical workings. For example, you might configure a 1TB RAID 5 array using three 500GB hard drives in hardware RAID, the operating system would simply be presented with a "single" 1TB volume. Software solutions are typically implemented in the operating system and would present the RAID drive as a single volume to applications running upon the operating system.

There are three key concepts in RAID: mirroring, the copying of data to more than one disk; striping, the splitting of data across more than one disk; and error correction, where redundant data is stored to allow problems to be detected and possibly fixed (known as fault tolerance). Different RAID levels use one or more of these techniques, depending on the system requirements. RAID's main aim can be either to improve reliability and availability of data, ensuring that important data is available more often than not (e.g. a database of customer orders), or merely to improve the access speed to files (e.g. for a system that delivers video on demand TV programs to many viewers).

RAID is a wide used fault-tolerance technology that provide a duplication of data stored across drives so that if a drive fails, the other drives in the solution can provide the data. The benefit is that if a drive fails, you can wait to fix the problem at the end of the business day, knowing that the redundancy of your solution will take care of the missing data.

There are different types of RAID, known as levels, and each level provides a different benefit with a different type of redundancy. The next parts of this group of posts will give you a full description of popular RAID levels supported by different network operating systems.

Normal storage concept.

Network Security Part 9 TACACS+ & AAA.

2009-11-02T23:07:00.001+00:00

TACACS+:

In computer networking, TACACS+ (Terminal Access Controller Access-Control System Plus) is a protocol which provides access control for routers, network access servers and other networked computing devices via one or more centralized servers. TACACS+ provides separate authentication, authorization and accounting services.

TACACS+ is based on TACACS, but, in spite of its name, it is an entirely new protocol which is incompatible with any previous version of TACACS. TACACS+ and RADIUS have generally replaced the earlier protocols in more recently built or updated networks, although TACACS and XTACACS are still running on many older systems.

TACACS+ Server.

Authentication, Authorization and Accounting (AAA):
Whereas RADIUS combines authentication and authorization in a user profile, TACACS+ separates the two operations. Another difference is that TACACS+ uses the Transmission Control Protocol (TCP) while RADIUS uses the User Datagram Protocol (UDP). Most administrators recommend using TACACS+ because TCP is seen as a more reliable protocol.

The extensions to the TACACS+ protocol provide for more types of authentication requests and more types of response codes than were in the original specification.

Network Security Part 8 VPN

2009-11-02T22:48:00.001+00:00

Virtual Private Network:

A virtual private network (VPN) is a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. The link-layer protocols of the virtual network are said to be tunneled through the larger network when this is the case. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features.

VPN Types:

Remote Access VPN.

SSL /web based RA-VPN.
Client based RA-VPN.

Site to Site VPN.

VPN connection types.

The key benefits that VPN technologies provide are:

Extend geographic connectivity
Greatly reduce operational costs when compared to traditional WAN technologies
Improve productivity
Provide support for home/remote working
Integrate well with existing broadband access technologies

They key functions which make VPN technologies secure are the following:

Authentication - Ensuring the communication is from a trusted source
Access Control - Preventing unauthorised users from accessing the network
Confidentiality - Preventing the reading or copying of data as it travels across the public network
Data integrity - Ensuring the data has not been tampered with as it travels across the public network

Network Security Part 7 Web Application Scanner.

2009-11-02T22:37:00.001+00:00

Web Application Scanner:

web application security scanner is program which communicates with a web application through the web front-end in order to identify potential security weaknesses in the web application.

It performs a black-box test. Unlike source code scanners, web application scanners don't have access to the source code and therefore detect vulnerabilities by actually performing attacks.

A web application security scanner can facilitate the automated review of a web application with the expressed purpose of discovering security vulnerabilities, and are required to comply with various regulatory requirements. Web application scanners can look for a wide variety of vulnerabilities, including:

Input/Output validation: (Cross-site scripting, SQL Injection)
Specific application problems
Server configuration mistakes/errors/version

Web Applications Issues :

Scripting issues
Sources of input: forms, text boxes, dialog windows, etc.
Multiple Charset Encodings (UTF-8, ISO-8859-15, UTF-7, etc.)
Regular expression checks
Header integrity (e.g. Multiple HTTP Content Length, HTTP Response Splitting)
Session handling/fixation
Cookies
Framework vulnerabities(Java Server Pages, .NET, Ruby On Rails, Django, etc.)
Success control: front door, back door vulnerability assessment
Penetration attempts versus failures

Technical vulnerabilities :

Unvalidated input:

Tainted parameters - Parameters users in URLs, HTTP headers, and forms are often used to control and validate access to sentitive information.
Tainted data

Cross-Site Scripting flaws:

XSS takes advantage of a vulnerable web site to attack clients who visit that web site. The most frequent goal is to steal the credentials of users who visit the site.

Content Injection flaws:

Data injection
SQL injection - SQL injection allows commands to be executed directly against the database, allowing disclosure and modification of data in the database
XPath injection - XPath injection allows attacker to manipulate the data in the XML database
Command injection - OS and platform commands can often be used to give attackers access to data and escalate privileges on backend servers.
Process injection
Cross-site Request Forgeries

Security Vulnerabilities :

Denial of Service
Broken access control
Path manipulation
Broken session management (synchronization timing problems)
Weak cryptographic functions, Non salt hash

Architectural/Logical Vulnerabilities :

Information leakage
Insufficient authentification
Password change form disclosing detailed errors
Session-idle deconstruction not consistent with policies
Spend deposit before deposit funds are validated

Other vulnerabilities :

Debug mode
Thread Safety
Hidden Form Field Manipulation
Weak Session Cookies: Cookies are often used to transit sensitive credentials, and are often easily modified to escalate access or assume another user's identify.
Fail Open Authentication
Dangers of HTML Comments

Web Scanner in network.

Network Security Part 6 Mail Relay.

2009-11-02T22:01:00.002+00:00

Mail Relay:

An SMTP open relay is a mail server that permits an unknown, outside sender to pass mail through the server to unknown, outside recipients, usually without the consent of its manager.

InterScan Messaging Security Appliance 7.0

The Trend Micro InterScan Messaging Security Appliance gives us a very comprehensive solution with built-in spam detection, anti-phishing, and IntelliTrap technology for detecting worms and viruses. We also get more aggressive spyware control by catching it in SMTP and POP3 streams. Since deploying the appliance, we’ve had no unwanted content on the network

InterScan Messaging Security System.

Network Security Part 5 IDS

2009-11-02T21:51:00.001+00:00

IDS:

The IDS “Intrusion Detection System” is software and/or hardware designed to detect unwanted attempts at accessing, manipulating, and/or disabling of computer systems, mainly through a network, such as the Internet. These attempts may take the form of attacks, as examples, by crackers, malware and/or disgruntled employees. An IDS cannot directly detect attacks within properly encrypted traffic.

An intrusion detection system is used to detect several types of malicious behaviors that can compromise the security and trust of a computer system. This includes network attacks against vulnerable services, data driven attacks on applications, host based attacks such as privilege escalation, unauthorized logins and access to sensitive files, and malware (viruses, trojan horses, and worms).

An IDS can be composed of several components: Sensors which generate security events, a Console to monitor events and alerts and control the sensors, and a central Engine that records events logged by the sensors in a database and uses a system of rules to generate alerts from security events received. There are several ways to categorize an IDS depending on the type and location of the sensors and the methodology used by the engine to generate alerts. In many simple IDS implementations all three components are combined in a single device or appliance.

Typical Intrusion Detection System.