"Linux_ notes" Linux Basics Common Sense _1

The notes are the result of watching Marco's Linux training video tutorial, after I have collated and released.

stability of the operating system:


The operating system itself is a program, his instructions and data and other applications stored in memory, if a malicious application can directly access the kernel, can directly interact with the kernel, can directly modify some data in the kernel, which means that the stability of the system will not be guaranteed, So there has to be a mechanism to isolate the application from the kernel, and typically, for example, Intel on a platform like this, he will provide the so-called protection mechanism, generally our CPU has 4 levels, is the concentric circle of four rings, the most inner layer we call the 0th ring (privilege level), only the kernel can be shipped Row in privileged mode, while other applications can only run at the outermost level, the middle two layer is useless, so any time the application is unable to access memory in the 0 level of memory area.


execution of the application:


There are two ways to start a program, one is to start automatically in the background (background service), and one is to start on Demand (interactive program)

Application execution Process: Tapping the keyboard to receive information is CPU,CPU do not know the meaning of the received information, the CPU first notify the kernel to handle, this time the kernel must be running on the CPU, the kernel knows The process is responsible for receiving this information, so the kernel is then forwarded to the application.

On-demand boot how can command the computer to start a program, how to let the operating system kernel can accept the user's command, ask us
A special application--shell must be provided to the operating system, including all the applications it provides.

Shell: Human-computer interface, graphical, command line-the entire operating system's shell, the ability to receive user instructions, understand the commands of the user command and transfer it to the kernel, the kernel command the micro program initiated by such an interface

The shell contains two types: The gui-graphical user interface cli-the command line interface

features of the operating system kernel:


Process Management (coordination of individual processes)
Memory management
Provide file system
Provides network functionality
Provides hardware drivers
Provide security mechanisms


the evolution of the operating system:


Batch processing system: the predecessor of modern operating system--JOBS1&&&&&&&JOBS2

In the event that the batch system is far from being able to perform its hardware, GE (GE), the American telephone and telegraph company Bell, and the AI Lab (MIT) of the MIT Institute of Technology combine three organizations to develop multi-tasking, multi-user systems, using assembly language for research and development, Developed a Multics (multiuser computer system)

After Bell Labs withdrew, Bell Labs had a technician called Ken Thompson, who developed a space travel game on Multics (it only runs on Multics) and Ken could no longer use it for free due to the exit of Bell Labs Multics The computing power provided, after applying for PDP-11 failure, he used PDP-7 to develop the UNICs running his game using assembly language.

UNICs performance is good, the transplant is more troublesome, a year later, he and colleagues Dennis Ritchie to the time of a B scripting language has been improved, making it a compiler language--c language, and use C language successfully rewritten UNICs, they co-signed in the United States computer Communications magazine Published a paper on the UNIX operating system, under the U.S. anti-monopoly law, they were forced to free to UNIX interested in the organization of colleges and universities and other free to provide UNIX learning.

In 76, Ken Hugh, who teaches at the University of California, Berkeley, and joins the BSRG organization, created by a graduate student Bill Joy, to study Unix,

Shortly thereafter, the rise of the U.S. military network required a protocol capable of transmitting data packets, BSRG the task, and shortly thereafter, control functions such as congestion control in the TCP protocol were born in the Unix version of BSRG, BSRG to soften their research into a separate Operating system BSD (Berkeley system distribution).

Bell Labs native UNIX is called the operating system: System [version number I 、... 、 v].

1996 Bell Labs was acquired, out of the constraints of not selling operating systems, and commercializing UNIX,

81 PC compatibility Machine was born, using a cp/m system developed by an American professor
Microsoft was founded in 81, from a programmer that bought a small system modeled after cp/m can run on a PC, and this system has been modified to name DOS and IBM cooperation.

After the PC was sold, jobs set up apple and later, Jobs bought Xerox's Park lab researchers ' copy of the mouse and graphical interface based on the UNIX operating system, and the Apple2 was released with a graphical interface.

Bill Gates issued the Windows operating system based on a copy from Apple-so jobs scolded Bill Gates as a thief.


BSD dissolution
BSD after the dissolution of its branch of the BSD research and development results:
freebsd--is mainly focused on running on the PC (Apple)
openbsd--focuses on safety
netbsd--mainly focuses on service

1982 Bill Joy Set up sun, the production station (the Sun OS later renamed Solaris).

Bill Joy introduced the CSH program to UNIX.

2009 Sun Company was acquired by Oracle,

DEC (about 71 years when one of the most famous production computer hosts of the company--ibm,dec) no longer uses VMS, Bill Gates will develop VMS team to introduce Microsoft to improve Windows, birth Windows NT (kernel VMS)

After Unix business, the original research institutions and colleges and universities can not free use of UNIX teaching, Dutch University professor Andrew modeled UNIX born Minix operating system for teaching use.

Professor at MIT in the 80: stallman--that the process was the crystallization of all human thought rather than the uniqueness of a rogue company, so he lifted the banner of freedom and advocated that the process was communist. The GNU was established.

Freedom: Free access, free revision, free learning

The GNU organization developed Emacs: text editor, Gcc:gnu c complier GNU C editor, bash: command line interface

Gnu:gnu is not Unix
GPL version:
Gpl:general Public liscense--Common license
lgpl:lesser--loose some of the GPL
GPLv2
GPLv3

Other open source organizations have made more permissive agreements (OpenSource: opensource):
Bsd
Apache

During this period, GNU lacked the UNIX kernel and the program failed to run.

University of Helsinki, Finland student Linus because Minix needs to install the driver manually, write out the Linux operating system and publish it on the bulletin board.

Linux has announced its accession to the GNU organization and GNU has kernel Linux.

Linux is just a kernel, and the complete Linux operating system is called Gnu/linux.

GNU's software and Linux kernel are all source code. It needs to be compiled into a binary computer to run.
Source code: A program developed using C. It needs to be compiled into a binary computer to run (cross-compile).
Cross-compiling: Runs on a CPU that is compiled on the B CPU.

The binary formats supported on the CPU are different, and this format is called: ABI (Application binary Interface)-- Referencing the binary interface

Third-party organizations are responsible for compiling the Linux kernel and various peripheral applications, and packaging and distributing them as an easy-to-install Linux.

Third party organizations (all following the GPL):
RedHat (founded in 1993 in North Carolina State, USA)
SLS (1991)
Debian (a researcher in Germany around 1992)--The only organization not supported by business organizations--the owner (who is responsible for maintaining Debian) is from the Internet, Technology is the most advanced, but also the most difficult to use.
SUSE (three German university students) acquired by Novell

is responsible for compiling the source code format of Linux on a common computer platform to be compiled into a format, called Linux issuer.

Gnu/linux operating system: linus--core gnu--Software Maintenance Publisher-Packaging release

In order to facilitate the implementation of software, such as loading and unloading management operations with the software Manager:
DEBIAN–DPT redhat–rpm

Third-party organization profit method: charge the service charge.

Organizations based on Red Hat two releases:
CentOS (no service guarantee): Community Enterprise OS Community Business operating system-(community version of Red Hat ）

Fedora: Upgrade once every six months to provide a test environment for Red Hat Enterprise

Mandriva: The interface is beautiful--primarily for personal desktops

Based on two releases of Debian: The Ubuntu--debian interface is very good-looking, focusing mainly on the use of PC machines.
Ubuntu-based two-time release: mint--interface More Beautiful

Release version:
Linux (kernel version) (www.kernel.org)
RHEL (Red Hat Enterprise Edition-release version)

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"Linux_ notes" Linux Basics Common Sense _1