Inside Linux
What is Kernel? Explain with an example.
o The core of the LINUX system. Loaded at system startup (boot). Memory-resident control program.
o Manages the entire resources of the system, presenting them to you and every other user as a coherent system. Provides service to user applications such as device management, process scheduling, etc.
o Example functions performed by the kernel are:
§ Managing the machine's memory and allocating it to each process.
§ Scheduling the work is done by the CPU so that the work of each user is carried out as efficiently as is possible.
§ Accomplishing the transfer of data from one part of the machine to another
§ Interpreting and executing instructions from the shell
§ Enforcing file access permissions
o You do not need to know anything about the kernel in order to use a LINUX system. These details are provided for your information only.
What is Shell? Explain with an example.
o Whenever you log in to a Linux system you are placed in a shell program. The shell's prompt is usually visible at the cursor's position on your screen. To get your work done, you enter commands at this prompt.
o The shell is a command interpreter; it takes each command and passes it to the operating system kernel to be acted upon. It then displays the results of this operation on your screen.
o Several shells are usually available on any LINUX system, each with its own strengths and weaknesses.
o Different users may use different shells. Initially, your system administrator will supply a default shell, which can be overridden or changed. The most commonly available shells are:
§ Bourne shell (sh)
§ C shell (csh)
§ Korn shell (KSH)
§ TC Shell (tcsh)
§ Bourne Again Shell (bash)
o Each shell also includes its own programming language. Command files, called "shell scripts" are used to accomplish a series of tasks.
· Utilities
o LINUX provides several hundred utility programs often referred to as commands.
o Accomplish universal functions
§ editing
§ file maintenance
§ printing
§ sorting
§ programming support
§ online info etc.
o Modular: single functions can be grouped to perform more complex tasks
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