Archive for the ‘OS’ Category

Wow..it seems like google is planning to take over the world. This time its an OS from them and they call it the Google Chrome OS. The official blog calls it an “extension” of the Chrome browzer, they were kidding. Chrome OS is a lightweight, open-source PC-operating system that is built over the Linux kernel. And like most google products its supposed to be free of cost as well. Now thats a real deal..all the freedom of open-source and the support of a giant, thats most men’s dream.

The very concept the Chrome OS is that its the browzer thats the real OS. Most applications are kept online. Now what the OS is supposed to provide is a quick-starting light and power saving OS that can support this concept. Cynics might ask then how can it be a danger to the current  OS giant Microsoft when chrome is not designed for those power users out there at all. The issue gets strong when the figures show that most of the PC users are not the so called power users. They use PC to access the net, to stay in touch, to make words docs, spreadsheets and do presentations.People dont want to worry about carrying around files and searching out for drivers. Now for them Chrome is the answer to their prayers. And they are the majority. But of course those power users are gonna have a bad time with Chrome. Those like the multimedia eds and the gamers. But they are just a handfull in this world.

The announcement came this tuesday night and in just two days itself it has become one of the most discussed topics in the internet world. People are shooting questions on more detailed informations on the OS and its supports. Unconfirmed reports are coming from around the globe regarding Google negotiating with most OEMs invluding Dell, HP, Asus and Acer. But till this moement they havent given an official comment on that.And as far as the experts can think, it will be a good offer for those OEMs as well. Afterall it can save them around $50 per machine.Considering the ability of Chrome to run on X86 and ARM processors there is every reason to think chrome to be better suited for Netbooks than Windows.

However I was feeling like its Google’s vision into the future. They have already understood computing cannot be contained in a small box. They have realized cloud is the future. With the ability of clouds to share resources the internet becomes the backbone of all computing and all you will ever need is a browzer(what will a browzer look like at that time is something I cant predict).Now in that scenario, it will be the Chrome that makes the future. And what can we use Windows for then…perhaps to sit back and watch the clouds moving in the sky. I would like to quote a a few words I have read about this issue, “If indeed Google puts out a fast, easy to use operating system that lets netbooks soar and free users from constant software patches, Microsoft will find it very hard to explain to consumers why they should continue to use its software, other than just out of a foolish consistency.”

But at the end of the day,there is one thing that makes me wonder…what happened to the android project. HP already had plans to make it their OS for netbooks . Chrome is an entirely different OS and has nothing to do with the Android. Did they really drop the Android project or did they decide to keep it exclusive for the mobile devices. Man its Google. When they do something, there is always a purpose.

Netfilter is a subsystem in the Linux 2.4 kernel. Netfilter provides an generic and abstract interface to the standard routing code. This is currently used in Linux kernel for packet filtering, mangling, NAT(network address translation) and queuing packets to the userspace.I have been using netfilters in my final year project(in VoIP security) as a packet capture mechanism.Netfilter makes connection tracking possible through the use of various hooks in the kernel’s network code.

These hooks are places that kernel code, either statically built or in the form of a loadable module, can register functions to be called for specific network events. An example of such an event is the reception of a packet.

Linux , since 2.4,  supports hooks for IPv4 and IPv6. Netfilter defines five hooks for IPv4. The declaration of the symbols for these can be found in “linux/netfilter_ipv4.h”. These hooks are displayed in the table below:

Hook

Called at

NF_IP_PRE_ROUTING After sanity checks, before routing decisions.
NF_IP_LOCAL_IN After routing decisions if packet is for this host.
NF_IP_FORWARD If the packet is destined for another interface.
NF_IP_LOCAL_OUT Packets coming from local processes on their way out.
NF_IP_POST_ROUTING Just before outbound packets “hit the wire”.

The NF_IP_PRE_ROUTING hook, called as the first hook after a packet has been received, has been used for packet capture in this project. The following diagrams diagrammatically represents where exactly does each of these hooks operate at.

At any of these hooks we can define Callback functions which act as handler routines. These functions are invoked when the corresponding network event occurs. Now the fate of the packet is determined by the return code of the hook function. Various return codes available are:

Return Code

Meaning

NF_DROP Discard the packet.
NF_ACCEPT Keep the packet.
NF_STOLEN Forget about the packet.
NF_QUEUE Queue packet for userspace.
NF_REPEAT Call this hook function again.

The NF_DROP return code means that this packet should be dropped completely and any resources allocated for it should be released. NF_ACCEPT tells Netfilter that so far the packet is still acceptable and that it should move to the next stage of the network stack. NF_STOLEN is an interesting one because it tells Netfilter to “forget” about the packet. What this tells Netfilter is that the hook function will take processing of this packet from here and that Netfilter should drop all processing of it. This does not mean, however, that resources for the packet are released. The packet and it’s respective sk_buff structure are still valid, it’s just that the hook function has taken ownership of the packet away from Netfilter. Unfortunately I’m not exactly clear on what NF_QUEUE really does so for now I won’t discuss it. The last return value, NF_REPEAT requests that Netfilter calls the hook function again. Obviously one must be careful using NF_REPEAT so as to avoid an endless loop.

I will try to add more details on the same with sample codes in my future posts.

PS: The post contains adopted contents. Content was actually prepared for the project documentation purpose.

Standard Original IBM POST Error Codes

Posted: May 19, 2009 in OS, trivia
Tags: ,

1 short beep

Normal POST – system is ok
2 short beeps POST Error – error code shown on screen
No beep Power supply or system board problem
Continuous beep Power supply, system board, or keyboard problem
Repeating short beeps Power supply or system board problem
1 long, 1 short beep System board problem
1 long, 2 short beeps Display adapter problem (MDA, CGA)
1 long, 3 short beeps Enhanced  Graphics Adapter (EGA)
3 long beeps 3270 keyboard card

Finally the much awaited Ubuntu 9.04 has released. Although I didnt yet install and use it, I hearing a lot of noise about it, especially as a total replacement to Windows. One thing I am hearing the most is about the speed, and a faster loading time. I am really dying to compare it with the new Windows 7 RC1. But the rest of the stuff I hear are all based on some new applications that are bundled along with it. Like a new media player that can automatically download the subtitles from “open”subtitles.com and a package manager that can take a backup copy of all the packages and even perform an offline installation similar to apt-get.  But this package manager is still way below the windows counterpart where you install an application with just one button click.

The look and feel thing, from what I have seen, I feel the UI of windows 7 (i have been using the beta for sometime) is far better than that of Ubuntu.. W7 interface makes a lot of things easier to do..like connecting to network directly from the tray and those cool transparency effects. With that default themes of both, I felt like i went straight to the Sahara desert after my vacation in Bahamas.

But one major problem I am gonna have with Ubuntu is the lack of drivers…especially the graphics and sound drivers…I am having an nVidia 8600 GT graphics card and a creative audigy sound card to help play my Altec lansing. Ubuntu disappoints big time. Afterall all the money I saved on replacing windows with Ubuntu is lost counting the money I spent on these hardwares which are now nothing more than just sitting ducks. Thanks my speakers are having a stereo mode for atleast I can hear some sound,though very feeble.

And the gtalk..I live in Gtalk…whatever complaints they say about the little gadget from Google, I cant live without it..Now the only way continue using gtalk is to use something like Pidgin..but the bird never really talk..there is no voice support. Heard they are gonna pack it soon, but like most other opensource things, the date is still indefinite. I really wanna talk with my friends..especially when its “free”.

As a Computer Science student,graduating in about a week, I love ubuntu as a developers platform. Most of my projects projects including my final year project was done on Ubuntu. And my final project was actually to modify the kernel itself for performance tweaking. The support forum is good and the response come pretty fast. On the contrary for an authentic windows operating system, that support comes as a part of the bundle you ‘purchased’. And forget about the possiblity of me doing my final project on changing the Windows kernel(may be thats why windows is so stable..he he). Hmm..my friend Anirudh is working in Microsoft, may be he can one day tell me how does a windows kernel look like.And not to forget, they have made considerable enhancements to the kernel by Windows 7, finally coming up with the worlds most compact kernel.

Now lemme come back to where we started. Is 9.04 a complete replacement for windows. Honestly in my opinion, NOT YET. Because still if my mom wants to use a pc surfing the net or if my little brother wants to use my laptop for playing some games , then there is no way I am going to recommend an Ubuntu for them.I will buy them a W7 or a Vista. Ubuntu might be the favourite for all the developer folks,that wud include me too, but considering the common people and their needs, I think Ubuntu has a got a long way to go before u can really consider it as a replacement for windows. Not all people will need to see the kernel code before he starts using it. And the number of those common people who use computers are many many times greater than the number of dev guys around. I wonder why these Ubuntu people forget this simple thing. May be this is where the MS pro’s score over the weekend programmers..

PS: I am not against open source or a die hard fan of Microsoft. I have contributed to open source as well. Please dont misunderstand me.

Finally microsoft have finished working on Windows 7 RC 1, the most anticipated piece of software this year(lets not forget Ubuntu 9.04).Hmmm,I dont think the final release which is expected to happen later this year or early next year will not be a lot different than RC1.So this one will do the trick for most people.

Anyway make sure your PC is 7Ready. So here is the system hardware requirements:

  • 1GHz 32-bit or 64-bit processor
  • 1GB of RAM
  • 16GB of disk space (or 20GB for 64-bit users)
  • DirectX 9 graphics device with WDDM 1.0 or higher driver

If you want to use Windows XP Mode (which lets you run Windows XP programs), you’ll need at least 2GB of RAM and 15GB of additional storage space as well as a CPU that supports hardware virtualization.

Alright then…go run for it…I wish it works well for you..godspeed.

DTrace

Posted: April 19, 2009 in OS

Currently working on detrace from the Sun.Will update more after getting a bit forward.

Tech Trivia #4: Web filtering for dummies

Posted: April 16, 2009 in OS, trivia
Tags:

Is it a linux machine and you dont want your kids to be in some specific site,say facebook.com…well then you can put a list of those sites in the /etc/hosts file and add the following into it.

127.0.0.1        www.facebook.com

127.0.0.1        www.anysite.com

Yes its not a big deal but that would come handy for home use.