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Old June 9th, 2016, 02:39 PM
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Default Re: Notes for IP University

The notes on Linux for the bachelor of Computer Application Course offered by the IP University is as explained below:

What is Kernel in Linux ?

Ans : The Kernel is the center program that runs programs and oversees equipment gadgets, for example, circles and printers. It execute the charges which give by environment. Part gives an interface amongst shell and equipment.

Characterize the elements of Linux ?

Ans : 1. Multi-tasking :

Linux underpins genuine preemptive multi-tasking. All procedures run totally freely of each other. No procedure should be worried with making processor time accessible to different procedures.

Multi-client access :
A multi-client framework is a PC that can simultaneously and autonomously execute a few applications having a place with two or more clients.

Multi-handling :
Linux additionally keeps running on multi-processor designs. This implies the O. S. can appropriate a few applications over a few processors.

Design freedom (Portability) :
Linux keeps running on a few equipment stages, from the Amiga to the PC to DEC Alpha workstations. Such equipment autonomy is accomplished by no different genuine O. S.

Request load executables :
Just those parts of a system really required for execution are stacked into memory. At the point when another procedure is made utilizing fork(), memory is not asked for instantly, but rather the memory for the guardian procedure is utilized mutually by both procedures.

Paging :
Linux give an imperative idea of paging. Regardless of the best endeavors to utilize physical memory proficiently, it can happen that the accessible memory is completely taken up.

Dynamic store for hard circle :
Linux progressively conforms the span of store memory being used to suit the present memory utilization circumstance.

Shared Libraries :
Libraries are accumulations of schedules required by a project for preparing information. There are various standard libraries utilized by more than one procedure in the meantime.

Memory ensured mode :
Linux utilizes the processor's memory assurance instruments to keep the procedure from getting to memory allotted to the framework part or different procedures.

Support for national consoles and text styles :
Under Linux, an extensive variety of national consoles and character sets can be utilized : for instance, the Latin1 set characterized by the International Organization for Standardization (ISO) which likewise incorporates European extraordinary characters.

Diverse record frameworks :
Linux bolsters an assortment of record frameworks. The most ordinarily utilized record framework at present is the Second Extended (Ext2) File framework. This backings filenames of up to 255 characters and has various components making it more secure than ordinary Unix record frameworks.

Q. Characterize the document structure of Linux ?

Ans: The document structure of any O. S. is incorporates the plan of records and envelopes. Linux composes documents into a progressively associated set of registries. Every catalog may contain either documents or different indexes. On account of the similitudes to a tree, such a structure is regularly alluded to as a tree structure furthermore called guardian kid structure.

The Linux record structure branches into a few catalogs starting with a root index,/. Inside the root index a few framework registries contain documents and projects that are components of the Linux framework. These framework catalogs as takes after :-

/root : Begins the document framework structure, called the root

/fs : The virtual document framework interface in the fs index. The

executions of the different document frameworks upheld by LINUX are

held in the separate subdirectories.

/home : Contains clients' home indexes

/canister : Holds all the standard orders and utility projects

/usr : Holds those documents and charges utilized by the framework; this registry

separates into a few sub-index

/usr/canister : Holds client situated summons and utility projects

/usr/sbin : Holds framework organization orders

/usr/lib : Holds libraries for programming dialects

/usr/doc : Holds Linux documentation

/usr/man : Holds the online manual Man documents

/usr/spool : Holds spooled documents, for example, those produced for printing occupations and

system exchanges

/sbin : Holds framework organization orders for booting the framework

/var : Holds documents that shift, for example, post box records

/dev : Holds document interfaces for gadgets, for example, the terminals and printers

/and so on : Holds framework design records and whatever other framework documents.

/init : contains all the capacities expected to begin the piece. Like start_kernel().

/net : contains the executions of different system conventions and the

code for attachments to the UNIX and Internet spaces.

/curve : design - subordinate code is held in the subdirectories of curve/

/mm : contains Memory administration hotspots for the portion.

Characterize the Kernel Architecture ?

Ans : Most Unix portions are solid : every piece layer is incorporated into the entire bit system and urns in Kernel Mode in the interest of the present procedure. Microkernel working frameworks request a little arrangement of capacities from the bit, for the most part including a couple synchronization primitives, a basic scheduler, and an interprocess correspondence component. Despite the fact that Microkernels arranged O. S. are by and large slower than solid ones, since the express message going between the diverse layers of the O. S. might have some hypothetical points of interest over solid ones.

Characterize the procedure and task_structure ?

Ans : The idea of a procedure is essential to any multiprogramming working framework. A procedure is normally characterized as an occurrence of a system in execution; in this manner, if 16 clients are running vi without a moment's delay, there are 16 separate procedures ( despite the fact that they can have the same executable code).

Each and every procedure have some one of a kind data, which store in task_struct sort process descriptor, which is the object of task_struct.

Struct undertaking _struct
unstable long state;
long counter;
long need;
unsigned long flag;
unsigned since quite a while ago blocked;
unsigned long banners;
int errno;
int debugreg[8];
struct task_struct *next_task;
struct task_struct *prev_task;
struct mm_struct mm;
int pid, uid,gid;
struct fs_struct fs;
long utime, stime, cutime, cstime, start_time;
state field of the task_struct portrays what is at present event to the procedure. The accompanying are the conceivable procedure states :

TASK_RUNNING : The procedure is either executing on the CPU or holding up to be executed.

TASK_INTERRUPTIBLE : The procedure is suspended (dozing) until some condition turns out to be valid. Raising an equipment interfere, discharging a framework asset the procedure is sitting tight for, or conveying a sign are case of conditions that may awaken the procedure, that is returned its state to TASK_RUNNING.

TASK_UNINTERRUPTIBLE: In this state procedure is uninterruptible of any equipment interfere, or any sign.

TASK_STOPPED: Process execution has been ceased : the procedure enters this state in the wake of accepting a SIGSTOP, SIGTSTP, SIGTTIN, or SIGTTOU signal.

TASK_ZOMBIE : Process execution is ended, yet the guardian procedure has not halted. The portion can't dispose of the information contained in the dead procedure task_struct on the grounds that the guardian could require it.

The counter variable holds the time in "ticks" for which the procedure can in any case keep running before a required planning activity is done. The schedular utilizes the counter esteem to choose the following procedure.

The need holds the need of a procedure.

The sign variable contains a bit veil for signs got for the procedure.

The bolcked contains a bit veil for all the signs the procedure arrangements to handle later.

Banners contains the framework status banners.

errono contains the mistake code if created.

debugreg[8] allocates the debugger to that blunder code.

*next_task and *prev_task all procedures are entered in a doubly connected rundown with the assistance of these two segments.

mm_struct mm the information for every procedure required for memory administration are gathered, mm_struct store those information.

Each procedure has its own particular procedure ID number , pid, client ID, uid, goup ID, gid.

The document framework particular information are put away in fs_struct fs.

The utime and stime variables hold the time the procedure has spent in User Mode and System Mode, cutime and cstime contain the aggregates of the comparing times for all tyke forms, start_time contains the time at which the present procedure was produced.

Q. What is the yield of order ps ?

Ans : ps summon yield which procedures are running at any moment. Linux doles out a one of a kind number to each procedure running in memory. This number is called process ID or essentially PID.

2269 tty01 0:05 sh
2396 tty01 0:00 ps

PID : Process ID

TTY : Terminal Id Which The Processes Were Launched

TIME : The Time That Has Elapsed following the Processes Were Launched

Charge : The Names Of The Processes.

Part 4 : Memory Management

Q Define the engineering - free memory model in Linux ?

Ans : Memory Management is principally worried with distribution of fundamental memory to solicitations forms. Two critical components of memory administration capacity are : Protection and Sharing. Memory administration action in a Linux bit. Some of fundamental issues identified with memory administration are :

Pages of Memory :
The physical memory is isolated into pages. The measure of a memory page is characterized by the PAGE_SIZE large scale. For the x86 processor, the size is set to 4 KB, while the Alpha processor utilizes 8 KB.

Virtual location space :
A procedure is keep running in a virtual location space. In theory memory display, the virtual location space is organized as a part fragment in addition to a client section. Code and information for the piece can be gotten to in the bit section, and code and information for the procedure in the client portion. A virtual location is given by reference to a section selector and the counterbalance inside the portion. At the point when code is being prepared, the portion selector is as of now set and just balances are us
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