Tushar Sharma's Blog

Executable file in linux

tusharsharma43 — Wed, 12 Jan 2011 08:53:47 +0000

In GNU/Linux systems the file type is determined by its data context (a file is recognized by its data: a script begin with “#!/bin/sh”, an MP£ file with “ID3″, and MPEG file with 0xBA hex code… and so on). So the file extension become unusefull (because if I rename test.mp3 to test.exe or test.txt its data doesn’t change, and remains always an MP3 file and it is recognized as MP3 file). (see the file command!)

Executables files are recognizable by their data, but they can be executable only if it’s execution permission bit is set (do you know about permission bitmask???). If executable bit is set, and if the file is an executable recognized by the running kernel, the application starts.

An executable run with the permission of the caller: so if you run an application as user, the application have the permission of the user. If the user is “root”, the application can do anything root can do!

Then, certain executable can be run only with root permissions, because it may edit some configuration file or anything else. So the application can do its job only if the application was started by the administrator (root).

If any application need superuser privileges, but should be run by any user, executable file have an extra permission bit: the SUID bit (Set User ID). When this bit is set, the permissions at run time doesn’t depends on the application caller, but the file owner (do you about file owner/group?). So if application has SUID bit set and it’s owned by root, when any user run the SUID executable, run application with root privileges.

That’s because GNU/Linux system are harder to break. To modify system configuration (to introduce viruses, root kits, backdoors…) you should break services that runs with root provileges, otherwise none can modify the system. SUID application are very rare, and often they are secure. However, even if an application runs with root privileges, often it is closed into a limited sub-system (called root jail), wich is a minimal system “running” on top of the system. If application is break, it is limited into the minimal system, so it cannot iteract with the real system running.

2010 in review

tusharsharma43 — Mon, 03 Jan 2011 16:46:12 +0000

The stats helper monkeys at WordPress.com mulled over how this blog did in 2010, and here’s a high level summary of its overall blog health:

The Blog-Health-o-Meter™ reads This blog is doing awesome!.

Crunchy numbers

A helper monkey made this abstract painting, inspired by your stats.

A Boeing 747-400 passenger jet can hold 416 passengers. This blog was viewed about 2,000 times in 2010. That’s about 5 full 747s.

In 2010, there were 54 new posts, not bad for the first year! There were 11 pictures uploaded, taking up a total of 606kb. That’s about a picture per month.

The busiest day of the year was February 16th with 46 views. The most popular post that day was Windows Alternative on LInux..(use GNU/Linux).

Where did they come from?

The top referring sites in 2010 were facebook.com, google.co.in, cordless-homephone.info, google.com, and mail.yahoo.com.

Some visitors came searching, mostly for tushar sharma, tushar sharma blog, gate exam blog, lrpc, and gets function in linux.

Attractions in 2010

These are the posts and pages that got the most views in 2010.

Windows Alternative on LInux..(use GNU/Linux) February 2010
2 comments

GATE EXAMINATION INFO January 2010
3 comments

What is the difference in virtual packet switching and datagram switching? what information does packets hold? February 2010

gets() function, the gnu c compiler gives a warning that it is dangerous to use gets() March 2010
1 comment

About Me : January 2010

how rss feed works

tusharsharma43 — Sat, 18 Dec 2010 17:23:05 +0000

Short for Really Simple Syndication or Rich Site Summary, this handy service is revolutionizing the way we search for content. In addition, us web searchers don’t necessarily have to keep checking back to any particular site to see if it’s been updated – all we need to do is subscribe to the RSS feed, much like you would subscribe to a newspaper, and then read the updates from the site, delivered via RSS feeds, in what’s called a “feed reader.” (We’ll get to feed readers in just a minute!) RSS feeds benefit those who actually own or publish a website as well, since site owners can get their updated content to subscribers fast by submitting feeds to various XML and RSS directories. How do RSS feeds work? RSS feeds really couldn’t be simpler. They’re basically simple text files that, once submitted to feed directories, will allow subscribers to see content within a very short time after it’s updated (sometimes as short as 30 minutes or less; it’s getting faster all the time). This content can be aggregated to be viewed even more easily by using a feed reader. I’ve written up an article on the best feed readers out there. A feed reader, or feed aggregator, is just a really simple way to view all your feeds at one time via one interface. For instance, I have a Bloglines feed. I have all sorts of good stuff in there. Can you imagine how much time it saves me to have all these topics sent to me in one place rather than me searching it out? In addition, all these people who have their sites syndicated on my Bloglines roll are enabling their content to be seen by me and other people who wouldn’t necessarily find them in the search engines or directories. RSS feeds are a wonderful resource, and the uses for RSS are only just beginning to be realized; not only for search engines and searching, but in how we optimize our sites.

OpenSuse

tusharsharma43 — Sat, 02 Oct 2010 06:27:59 +0000

open suse is one of finest Linux distro i have used, and am in love with that.

Latest openSuse11.3 LI-F-E have bundled up every required package right from Multimedia,Development, Networking, Useful pdf’s of howto use Opensuse and tonnes of s/w.

It has Ext4 file system default, GNOME, kde , GNOME 3 preview and other environment. I really like all desktop features.

for more visit official site for opensuse.

Redhat Linux History

tusharsharma43 — Sat, 02 Oct 2010 06:20:36 +0000

Redhat LInux History :–

Red Hat History

1968

ARPANET founded. The precursor to the Internet, it allows researchers to share code and information.

1969

Ken Thompson, researcher at Bell Labs, writes the first version of Unix.

1979

AT&T announces plans to commercialize Unix.

1983

Richard Stallman establishes the Free Software Foundation at MIT. The GNU project to construct an operating system based on Unix but for which the source code is freely available, begins. Stallman also establishes the idea of “copyleft” and the General Public License (GPL).

1987

Andrew Tanenbaum releases Minix, a version of Unix for the PC, Mac, Amiga, and Atari ST. Source code included.

1989

Michael Tiemann (Red Hat Vice President, Open Source Affairs) co-founds Cygnus Solutions, the first business to provide custom engineering and support services for free software.

1991

Linus Torvalds releases the Linux kernel.

Bob Young introduced to free software and UNIX by the system administrators of the New York City UNIX Users Group (Unigroup).

1993

Young incorporates ACC Corporation, a catalog business that sells Linux and Unix software accessories and books and distributes a magazine called New York UNIX

1994

Marc Ewing creates his own distribution of Linux which he names Red Hat Linux. Released in October, it becomes known as the Halloween release.

1995

Young buys Ewing’s business, merges it with ACC Corporation, and names the new company Red Hat Software.

Red Hat Linux 2.0 is released, officially unveils the new package management system called RPM.

1996

Red Hat opens sales and administration functions to North Carolina, opens corporate headquarters in Durham.

1997

January

Greylock and August Capital invest $6.25 million in Cygnus Solutions, become first VCs to invest in a free software business.

May

Eric Raymond delivers “The Cathedral and the Bazaar” at the Linux Kongress in Germany.

The Red Hat training model and the term “Red Hat Certified Engineer” are first developed as the benchmark for technical skills required of Red Hat Support Partners worldwide.

July

Red Hat Linux 4.2 released.

December

Red Hat announces Red Hat Linux 5.0, followed by the introduction of telephone technical support.

1998

January

Netscape announces plans to make the source code for Communicator free on the Internet.

February

Term “Open Source” is coined in Palo Alto, CA.

July

Oracle, CA, and Informix announce support for Red Hat Linux.

November

A lawyer for Microsoft brandishes a box of Red Hat Linux in an attempt to refute Justice Department charges that the software giant has a monopoly on the operating system market.

December

The first formal RHCE training course, class sessions and dates, and the RHCE Exam are announced.

IDC reports that Linux installations grew by 212% from the previous year, outpacing growth rates of Unix, Windows NT, Netware, and all other server operating systems.

1999

February

IBM and Red Hat announce Linux Alliance.

April

Dell becomes the first major computer vendor to factory-install Red Hat Linux on servers and workstations.

Red Hat Linux 6.0 released.

July

Red Hat expands European presence, opening offices in the United Kingdom and Germany.

August

Red Hat goes public, the eighth-biggest first-day gain in Wall Street history.

September

Red Herring names Bob Young one of the “Top 10 Entrepreneurs of 1999.”

Red Hat announces expansion into Japan.

October

Red Hat releases Red Hat Linux 6.1.

November

Matthew Szulik promoted to CEO. Red Hat Named One of the Top 20 “Best Regarded” Technology Companies, Top 10 for “Vision and Leadership” in Harris Interactive survey.

Red Hat acquires Cygnus, creating the largest open source company in the world.

for more :–here is the link :–

http://www.redhat.com/about/companyprofile/history/

Linux History by Linus Torvalds

tusharsharma43 — Fri, 01 Oct 2010 17:03:30 +0000

here is the link :-

http://www.cs.cmu.edu/~awb/linux.history.html

Linus Torvalds post

tusharsharma43 — Fri, 01 Oct 2010 17:00:15 +0000

  From: torvalds@klaava.Helsinki.FI (Linus Benedict Torvalds)
  Newsgroups: comp.os.minix
  Subject: What would you like to see most in minix?
  Summary: small poll for my new operating system
  Message-ID:
  Date: 25 Aug 91 20:57:08 GMT
  Organization: University of Helsinki

  Hello everybody out there using minix -

  I'm doing a (free) operating system (just a hobby, won't be big and
  professional like gnu) for 386(486) AT clones.  This has been brewing
  since april, and is starting to get ready.  I'd like any feedback on
  things people like/dislike in minix, as my OS resembles it somewhat
  (same physical layout of the file-system (due to practical reasons)
  among other things).

  I've currently ported bash(1.08) and gcc(1.40), and things seem to work.
  This implies that I'll get something practical within a few months, and
  I'd like to know what features most people would want.  Any suggestions
  are welcome, but I won't promise I'll implement them  

                Linus (torvalds@kruuna.helsinki.fi)

  PS.  Yes - it's free of any minix code, and it has a multi-threaded fs.
  It is NOT protable (uses 386 task switching etc), and it probably never
  will support anything other than AT-harddisks, as that's all I have  .

difference between shells

tusharsharma43 — Fri, 01 Oct 2010 16:52:00 +0000

                                     sh   csh  ksh  bash tcsh zsh  rc   es
Job control                          N    Y    Y    Y    Y    Y    N    N
Aliases                              N    Y    Y    Y    Y    Y    N    N
Shell functions                      Y(1) N    Y    Y    N    Y    Y    Y
"Sensible" Input/Output redirection  Y    N    Y    Y    N    Y    Y    Y
Directory stack                      N    Y    Y    Y    Y    Y    F    F
Command history                      N    Y    Y    Y    Y    Y    L    L
Command line editing                 N    N    Y    Y    Y    Y    L    L
Vi Command line editing              N    N    Y    Y    Y(3) Y    L    L
Emacs Command line editing           N    N    Y    Y    Y    Y    L    L
Rebindable Command line editing      N    N    N    Y    Y    Y    L    L
User name look up                    N    Y    Y    Y    Y    Y    L    L
Login/Logout watching                N    N    N    N    Y    Y    F    F
Filename completion                  N    Y(1) Y    Y    Y    Y    L    L
Username completion                  N    Y(2) Y    Y    Y    Y    L    L
Hostname completion                  N    Y(2) Y    Y    Y    Y    L    L
History completion                   N    N    N    Y    Y    Y    L    L
Fully programmable Completion        N    N    N    N    Y    Y    N    N
Mh Mailbox completion                N    N    N    N(4) N(6) N(6) N    N
Co Processes                         N    N    Y    N    N    Y    N    N
Builtin artithmetic evaluation       N    Y    Y    Y    Y    Y    N    N
Can follow symbolic links invisibly  N    N    Y    Y    Y    Y    N    N
Periodic command execution           N    N    N    N    Y    Y    N    N
Custom Prompt (easily)               N    N    Y    Y    Y    Y    Y    Y
Sun Keyboard Hack                    N    N    N    N    N    Y    N    N
Spelling Correction                  N    N    N    N    Y    Y    N    N
Process Substitution                 N    N    N    Y(2) N    Y    Y    Y
Underlying Syntax                    sh   csh  sh   sh   csh  sh   rc   rc
Freely Available                     N    N    N(5) Y    Y    Y    Y    Y
Checks Mailbox                       N    Y    Y    Y    Y    Y    F    F
Tty Sanity Checking                  N    N    N    N    Y    Y    N    N
Can cope with large argument lists   Y    N    Y    Y    Y    Y    Y    Y
Has non-interactive startup file     N    Y    Y(7) Y(7) Y    Y    N    N
Has non-login startup file           N    Y    Y(7) Y    Y    Y    N    N
Can avoid user startup files         N    Y    N    Y    N    Y    Y    Y
Can specify startup file             N    N    Y    Y    N    N    N    N
Low level command redefinition       N    N    N    N    N    N    N    Y
Has anonymous functions              N    N    N    N    N    N    Y    Y
List Variables                       N    Y    Y    N    Y    Y    Y    Y
Full signal trap handling            Y    N    Y    Y    N    Y    Y    Y
File no clobber ability              N    Y    Y    Y    Y    Y    N    F
Local variables                      N    N    Y    Y    N    Y    Y    Y
Lexically scoped variables           N    N    N    N    N    N    N    Y
Exceptions                           N    N    N    N    N    N    N    Y

for more :http://www.unix.com/answers-frequently-asked-questions/12274-difference-between-ksh-bash-different-shells.html

LRPC Light Weight Remote Procedure Call

tusharsharma43 — Sun, 15 Aug 2010 04:59:17 +0000

LRPC – Lightweight Remote Procedure Call

There may be many popular meanings for LRPC with the most popular definition being that of Lightweight Remote Procedure Call

Lightweight Remote Procedure Call (LRPC) is a communication facility designed and optimized for
communication between protection domains on the same machine. In contemporary small-kernel
operating systems, existing RPC systems incur an unnecessarily high cost when used for the type of
communication that predominates-between protection domains on the same machine. This cost
leads system designers to coalesce weakly related subsystems into the same protection domain, trading
safety for performance. By reducing the overhead of same-machine communication, LRPC encourages
both safety and performance. LRPC combines the control transfer and communication model of
capability systems with the programming semantics and large-grained protection model of RPC.
LRPC achieves a factor-of-three performance improvement over more traditional approaches based
on independent threads exchanging messages, reducing the cost of same-machine communication to
nearly the lower bound imposed by conventional hardware,

if any one has any more idea, or info about this topic pls write here,,,,

openSUSE 11.3 Launch Party

tusharsharma43 — Thu, 15 Jul 2010 04:16:30 +0000

Date:	Saturday, July 17, 2010
Time:	5:00pm – 7:00pm
Location:	MS University of Vadodara, Computer Application Department