Hey guy's in this blog I'm going give an Overview on Linux Operating System, so let's start
added. Although it originally ran only on the 386 (and even had embedded 386 assembly code in the middle of C procedures), it was quickly ported to other platforms and now runs on a wide variety of machines, just as UNIX does. One difference with UNIX does stand out, however: Linux makes use of so many special
features of thegcc compiler and would need a lot of work before it would compile
with an ANSI standard C compiler. The shortsighted idea thatgcc is the only compiler the world will ever see is already becoming a problem because the opensource LLVM compiler from the University of Illinois is rapidly gaining many
adherents due to its flexibility and code quality. Since LLVM does not support all
the nonstandardgcc extensions to C, it cannot compile the Linux kernel without a
lot of patches to the kernel to replace non-ANSI code.
The next major release of Linux was version 1.0, issued in 1994. It was about
165,000 lines of code and included a new file system, memory-mapped files, and
BSD-compatible networking with sockets and TCP/IP. It also included many new
device drivers. Several minor revisions followed in the next two years.
By this time, Linux was sufficiently compatible with UNIX that a vast amount
of UNIX software was ported to Linux, making it far more useful than it would
have otherwise been. In addition, a large number of people were attracted to Linux
and began working on the code and extending it in many ways under Torvalds’
general supervision.
The next major release, 2.0, was made in 1996. It consisted of about 470,000
lines of C and 8000 lines of assembly code. It included support for 64-bit architectures, symmetric multiprogramming, new networking protocols, and numerous
other features. A large fraction of the total code mass was taken up by an extensive
collection of device drivers for an ever-growing set of supported peripherals. Additional releases followed frequently.
The version numbers of the Linux kernel consist of four numbers,A.B.C.D,
such as 2.6.9.11. The first number denotes the kernel version. The second number
denotes the major revision. Prior to the 2.6 kernel, even revision numbers corresponded to stable kernel releases, whereas odd ones corresponded to unstable revisions, under development. With the 2.6 kernel that is no longer the case. The third
number corresponds to minor revisions, such as support for new drivers. The fourth
number corresponds to minor bug fixes or security patches. In July 2011 Linus
Torvalds announced the release of Linux 3.0, not in response to major technical advances, but rather in honor of the 20th anniversary of the kernel. As of 2013, the
Linux kernel consists of close to 16 million lines of code.
A large array of standard UNIX software has been ported to Linux, including
the popular X Window System and a great deal of networking software. Two different GUIs (GNOME and KDE), which compete with each other, hav e also been
written for Linux. In short, it has grown to a full-blown UNIX clone with all the
bells and whistles a UNIX lover might conceivably want
One unusual feature of Linux is its business model: it is free software. It can
be downloaded from various sites on the Internet, for example:www.kernel.org.
Linux comes with a license devised by Richard Stallman, founder of the Free Software Foundation. Despite the fact that Linux is free, this license, theGPL (GNU
Public License), is longer than Microsoft’s Windows license and specifies what
you can and cannot do with the code. Users may use, copy, modify, and redistribute the source and binary code freely. The main restriction is that all works
derived from the Linux kernel may not be sold or redistributed in binary form only;
the source code must either be shipped with the product or be made available on
request.
printer, including options to include running heads, page numbers, and so on.
Compilers and programming tools includegcc, which calls the C compiler, andar, which collects library procedures into archive files.
Another important tool ismake, which is used to maintain large programs
whose source code consists of multiple files. Typically, some of these areheader
files, which contain type, variable, macro, and other declarations. Source files often
include these using a specialinclude directive. This way, two or more source files
can share the same declarations. However, if a header file is modified, it is necessary to find all the source files that depend on it and recompile them. The function
ofmake is to keep track of which file depends on which header, and similar things,
and arrange for all the necessary compilations to occur automatically. Nearly all
Linux programs, except the smallest ones, are set up to be compiled withmake.
A selection of the POSIX utility programs is listed in Fig. 10-2, along with a
short description of each. All Linux systems have them and many more.
Linux Operating system
Linux is the world’s most dominant operating system. Launched in 1991 by Linus Torvalds, it’s the gold standard of user-led open source innovation, representing Linus’ desire for an OS that he could run on his personal computer.
Since those early days, developers from large hardware companies to small emerging technology providers have contributed to Linux, building solutions that run on top of the open-source OS.
Since those early days, developers from large hardware companies to small emerging technology providers have contributed to Linux, building solutions that run on top of the open-source OS.
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| Linux Operating System |
The interface of Linux Operating System
The interface of the Linux is very simple and not a good User interface you can see here this is a screenshot of the linux operating system that you can understand well.
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| The interface of Linux Operating System |
Linux
During the early years of MINIX development and discussion on the Internet,
many people requested (or in many cases, demanded) more and better features, to
which the author often said ‘‘No’’ (to keep the system small enough for students to
understand completely in a one-semester university course). This continuous
‘‘No’’ irked many users. At this time, FreeBSD was not available, so that was not
an option. After a number of years went by like this, a Finnish student, Linus Torvalds, decided to write another UNIX clone, namedLinux, which would be a fullblown production system with many features MINIX was initially lacking. The
first version of Linux, 0.01, was released in 1991. It was cross-developed on a
MINIX machine and borrowed numerous ideas from MINIX, ranging from the
structure of the source tree to the layout of the file system. However, it was a
monolithic rather than a microkernel design, with the entire operating system in the
kernel. The code totaled 9300 lines of C and 950 lines of assembler, roughly similar to MINIX version in size and also comparable in functionality. De facto, it was
a rewrite of MINIX, the only system Torvalds had source code for Linux rapidly grew in size and evolved into a full, production UNIX clone, as
virtual memory, a more sophisticated file system, and many other features weremany people requested (or in many cases, demanded) more and better features, to
which the author often said ‘‘No’’ (to keep the system small enough for students to
understand completely in a one-semester university course). This continuous
‘‘No’’ irked many users. At this time, FreeBSD was not available, so that was not
an option. After a number of years went by like this, a Finnish student, Linus Torvalds, decided to write another UNIX clone, namedLinux, which would be a fullblown production system with many features MINIX was initially lacking. The
first version of Linux, 0.01, was released in 1991. It was cross-developed on a
MINIX machine and borrowed numerous ideas from MINIX, ranging from the
structure of the source tree to the layout of the file system. However, it was a
monolithic rather than a microkernel design, with the entire operating system in the
kernel. The code totaled 9300 lines of C and 950 lines of assembler, roughly similar to MINIX version in size and also comparable in functionality. De facto, it was
a rewrite of MINIX, the only system Torvalds had source code for Linux rapidly grew in size and evolved into a full, production UNIX clone, as
added. Although it originally ran only on the 386 (and even had embedded 386 assembly code in the middle of C procedures), it was quickly ported to other platforms and now runs on a wide variety of machines, just as UNIX does. One difference with UNIX does stand out, however: Linux makes use of so many special
features of thegcc compiler and would need a lot of work before it would compile
with an ANSI standard C compiler. The shortsighted idea thatgcc is the only compiler the world will ever see is already becoming a problem because the opensource LLVM compiler from the University of Illinois is rapidly gaining many
adherents due to its flexibility and code quality. Since LLVM does not support all
the nonstandardgcc extensions to C, it cannot compile the Linux kernel without a
lot of patches to the kernel to replace non-ANSI code.
The next major release of Linux was version 1.0, issued in 1994. It was about
165,000 lines of code and included a new file system, memory-mapped files, and
BSD-compatible networking with sockets and TCP/IP. It also included many new
device drivers. Several minor revisions followed in the next two years.
By this time, Linux was sufficiently compatible with UNIX that a vast amount
of UNIX software was ported to Linux, making it far more useful than it would
have otherwise been. In addition, a large number of people were attracted to Linux
and began working on the code and extending it in many ways under Torvalds’
general supervision.
The next major release, 2.0, was made in 1996. It consisted of about 470,000
lines of C and 8000 lines of assembly code. It included support for 64-bit architectures, symmetric multiprogramming, new networking protocols, and numerous
other features. A large fraction of the total code mass was taken up by an extensive
collection of device drivers for an ever-growing set of supported peripherals. Additional releases followed frequently.
The version numbers of the Linux kernel consist of four numbers,A.B.C.D,
such as 2.6.9.11. The first number denotes the kernel version. The second number
denotes the major revision. Prior to the 2.6 kernel, even revision numbers corresponded to stable kernel releases, whereas odd ones corresponded to unstable revisions, under development. With the 2.6 kernel that is no longer the case. The third
number corresponds to minor revisions, such as support for new drivers. The fourth
number corresponds to minor bug fixes or security patches. In July 2011 Linus
Torvalds announced the release of Linux 3.0, not in response to major technical advances, but rather in honor of the 20th anniversary of the kernel. As of 2013, the
Linux kernel consists of close to 16 million lines of code.
A large array of standard UNIX software has been ported to Linux, including
the popular X Window System and a great deal of networking software. Two different GUIs (GNOME and KDE), which compete with each other, hav e also been
written for Linux. In short, it has grown to a full-blown UNIX clone with all the
bells and whistles a UNIX lover might conceivably want
One unusual feature of Linux is its business model: it is free software. It can
be downloaded from various sites on the Internet, for example:www.kernel.org.
Linux comes with a license devised by Richard Stallman, founder of the Free Software Foundation. Despite the fact that Linux is free, this license, theGPL (GNU
Public License), is longer than Microsoft’s Windows license and specifies what
you can and cannot do with the code. Users may use, copy, modify, and redistribute the source and binary code freely. The main restriction is that all works
derived from the Linux kernel may not be sold or redistributed in binary form only;
the source code must either be shipped with the product or be made available on
request.
Linux Utility Programs
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Linux Utility Programs
|
The command-line (shell) user interface to Linux consists of a large number of
standard utility programs. Roughly speaking, these programs can be divided into
six categories, as follows:
1. File and directory manipulation commands.
2. Filters.
3. Program development tools, such as editors and compilers.
4. Text processing.
5. System administration.
6. Miscellaneous.
The POSIX 1003.1-2008 standard specifies the syntax and semantics of about 150
of these, primarily in the first three categories. The idea of standardizing them is to
make it possible for anyone to write shell scripts that use these programs and work
on all Linux systems.
In addition to these standard utilities, there are many application programs as
well, of course, such as Web browsers, media players, image viewers, office suites,
games, and so on.
Let us consider some examples of these programs, starting with file and directory manipulation.cp a bcopies file a to b, leaving the original file intact. In contrast,mv a bcopies a to b but removes the original. In effect, it moves the file rather than really
making a copy in the usual sense. Several files can be concatenated usingcat,
which reads each of its input files and copies them all to standard output, one after
another. Files can be removed by therm command. The chmod command allows
the owner to change the rights bits to modify access permissions. Directories can
be created withmkdir and removed with rmdir. To see a list of the files in a directory, ls can be used. It has a vast number of flags to control how much detail about
each file is shown (e.g., size, owner, group, creation date), to determine the sort
order (e.g., alphabetical, by time of last modification, reversed), to specify the layout on the screen, and much more.
We hav e already seen several filters:grep extracts lines containing a given pattern from standard input or one or more input files; sort sorts its input and writes it
on standard output;head extracts the initial lines of its input; tail extracts the final
lines of its input. Other filters defined by 1003.2 arecut and paste, which allow columns of text to be cut and pasted into files; od, which converts its (usually binary) input to ASCII text, in octal, decimal, or hexadecimal; tr, which does character
translation (e.g., lowercase to uppercase), and pr, which formats output for thestandard utility programs. Roughly speaking, these programs can be divided into
six categories, as follows:
1. File and directory manipulation commands.
2. Filters.
3. Program development tools, such as editors and compilers.
4. Text processing.
5. System administration.
6. Miscellaneous.
The POSIX 1003.1-2008 standard specifies the syntax and semantics of about 150
of these, primarily in the first three categories. The idea of standardizing them is to
make it possible for anyone to write shell scripts that use these programs and work
on all Linux systems.
In addition to these standard utilities, there are many application programs as
well, of course, such as Web browsers, media players, image viewers, office suites,
games, and so on.
Let us consider some examples of these programs, starting with file and directory manipulation.cp a bcopies file a to b, leaving the original file intact. In contrast,mv a bcopies a to b but removes the original. In effect, it moves the file rather than really
making a copy in the usual sense. Several files can be concatenated usingcat,
which reads each of its input files and copies them all to standard output, one after
another. Files can be removed by therm command. The chmod command allows
the owner to change the rights bits to modify access permissions. Directories can
be created withmkdir and removed with rmdir. To see a list of the files in a directory, ls can be used. It has a vast number of flags to control how much detail about
each file is shown (e.g., size, owner, group, creation date), to determine the sort
order (e.g., alphabetical, by time of last modification, reversed), to specify the layout on the screen, and much more.
We hav e already seen several filters:grep extracts lines containing a given pattern from standard input or one or more input files; sort sorts its input and writes it
on standard output;head extracts the initial lines of its input; tail extracts the final
lines of its input. Other filters defined by 1003.2 arecut and paste, which allow columns of text to be cut and pasted into files; od, which converts its (usually binary) input to ASCII text, in octal, decimal, or hexadecimal; tr, which does character
printer, including options to include running heads, page numbers, and so on.
Compilers and programming tools includegcc, which calls the C compiler, andar, which collects library procedures into archive files.
Another important tool ismake, which is used to maintain large programs
whose source code consists of multiple files. Typically, some of these areheader
files, which contain type, variable, macro, and other declarations. Source files often
include these using a specialinclude directive. This way, two or more source files
can share the same declarations. However, if a header file is modified, it is necessary to find all the source files that depend on it and recompile them. The function
ofmake is to keep track of which file depends on which header, and similar things,
and arrange for all the necessary compilations to occur automatically. Nearly all
Linux programs, except the smallest ones, are set up to be compiled withmake.
A selection of the POSIX utility programs is listed in Fig. 10-2, along with a
short description of each. All Linux systems have them and many more.
| Program | Typical use |
| cat | Concatenate multiple files to standard output |
| chmod | Change file protection mode |
| cp | Copy one or more files |
| cut | Cut columns of text from a file |
| grep | Search a file for some pattern |
| head | Extract the first lines of a file |
| ls | List director y |
| make | Compile files to build a binary |
| mkdir | Make a director y |
| od | Octal dump a file |
| paste | Paste columns of text into a file |
| pr | Format a file for printing |
| ps | List running processes |
| rm | Remove one or more files |
| rmdir | Remove a director y |
| sor t | Sor t a file of lines alphabetically |
| tail | Extract the last lines of a file |
| tr | Translate between character sets |
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