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55 lines
1.5 KiB
55 lines
1.5 KiB
= An Introduction to Linux !
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Apostolos rootApostolos@swarmlab.io
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// Metadata:
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:description: Intro and Install
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:keywords: Linux, apt
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:data-uri:
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:toc: right
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:toc-title: Table of contents
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:toclevels: 4
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:source-highlighter: highlight
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:no-header-footer:
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:nofooter:
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:last-update-label!:
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:icons: font
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:sectnums:
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== process
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An instance of a running program is called a process.
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Every time you run a shell command, a program is run and a process is created for it.
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In any modern operating system there can be more than one instance of a program loaded in memory at the same time.
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== Linux process management
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Operating systems need some ways to create processes.
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* In a very simple system designed for running only a single application (e.g., the controller in a microwave oven), it may be possible to have all the processes that will ever be needed be present when the system comes up.
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* In general-purpose systems, however, some way is needed to create and terminate processes as needed during operation.
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[NOTE]
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====
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*There are four principal events that cause a process to be created:*
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* System initialization.
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* Execution of process creation system call by a running process.
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* A user request to create a new process.
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* Initiation of a batch job.
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====
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Process creation in UNIX and Linux are done through *fork()* or *clone()* system calls.
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There are several steps involved in process creation.
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* process scheduling,
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* interrupt handling,
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* signaling,
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* process prioritization,
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* process switching,
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* process state,
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* process memory
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