Chapter 4 Kernel Initialization (Init)
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Tutorials Point, Simply Easy Learning
Tutorials Point, Simply Easy Learning UML Tutorial Tutorialspoint.com UNIX is a computer Operating System which is capable of handling activities from multiple users at the same time. Unix was originated around in 1969 at AT&T Bell Labs by Ken Thompson and Dennis Ritchie. This tutorial gives an initial push to start you with UNIX. For more detail kindly check tutorialspoint.com/unix What is Unix ? The UNIX operating system is a set of programs that act as a link between the computer and the user. The computer programs that allocate the system resources and coordinate all the details of the computer's internals is called the operating system or kernel. Users communicate with the kernel through a program known as the shell. The shell is a command line interpreter; it translates commands entered by the user and converts them into a language that is understood by the kernel. Unix was originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna. There are various Unix variants available in the market. Solaris Unix, AIX, UP Unix and BSD are few examples. Linux is also a flavour of Unix which is freely available. Several people can use a UNIX computer at the same time; hence UNIX is called a multiuser system. A user can also run multiple programs at the same time; hence UNIX is called multitasking. Unix Architecture: Here is a basic block diagram of a UNIX system: 1 | P a g e Tutorials Point, Simply Easy Learning The main concept that unites all versions of UNIX is the following four basics: Kernel: The kernel is the heart of the operating system. -
Introduction Use Runit with Traditional Init (Sysvinit)
2021/07/26 19:10 (UTC) 1/12 Runit Runit Introduction runit is a UNIX init scheme with service supervision. It is a cross-platform Unix init scheme with service supervision, a replacement for sysvinit, and other init schemes and supervision that are used with the traditional init. runit is compatible with djb's daemontools. In Unix-based computer operating systems, init (short for initialization) is the first process started during booting of the computer system. Init is a daemon process that continues running until the system is shut down. Slackware comes with its own legacy init (/sbin/init) from the sysvinit package, that used to be included in almost all other major Linux distributions. The init daemon (or its replacement) is characterised by Process ID 1 (PID 1). To read on the benefits of runit, see here: http://smarden.org/runit/benefits.html * Unless otherwise stated, all commands in this article are to be run by root. Use runit with traditional init (sysvinit) runit is not provided by Slackware, but a SlackBuild is maintained on https://slackbuilds.org/. It does not have any dependencies. As we do not want yet to replace init with runit, run the slackbuild with CONFIG=no: CONFIG=no ./runit.SlackBuild Then install the resulting package and proceed as follows: mkdir /etc/runit/ /service/ cp -a /usr/doc/runit-*/etc/2 /etc/runit/ /sbin/runsvdir-start & Starting via rc.local For a typical Slackware-stlyle service, you can edit /etc/rc.d/rc.local file if [ -x /sbin/runsvdir-start ]; then /sbin/runsvdir-start & fi and then edit write /etc/rc.d/rc.local_shutdown #!/bin/sh SlackDocs - https://docs.slackware.com/ Last update: 2020/05/06 08:08 (UTC) howtos:slackware_admin:runit https://docs.slackware.com/howtos:slackware_admin:runit RUNIT=x$( /sbin/pidof runsvdir ) if [ "$RUNIT" != x ]; then kill $RUNIT fi Then give rc.local_shutdown executive permission: chmod +x /etc/rc.d/rc.local_shutdown and reboot Starting via inittab (supervised) Remove the entries in /etc/rc.d/rc.local and /etc/rc.d/rc.local_shutdown described above. -
Mac OS X: an Introduction for Support Providers
Mac OS X: An Introduction for Support Providers Course Information Purpose of Course Mac OS X is the next-generation Macintosh operating system, utilizing a highly robust UNIX core with a brand new simplified user experience. It is the first successful attempt to provide a fully-functional graphical user experience in such an implementation without requiring the user to know or understand UNIX. This course is designed to provide a theoretical foundation for support providers seeking to provide user support for Mac OS X. It assumes the student has performed this role for Mac OS 9, and seeks to ground the student in Mac OS X using Mac OS 9 terms and concepts. Author: Robert Dorsett, manager, AppleCare Product Training & Readiness. Module Length: 2 hours Audience: Phone support, Apple Solutions Experts, Service Providers. Prerequisites: Experience supporting Mac OS 9 Course map: Operating Systems 101 Mac OS 9 and Cooperative Multitasking Mac OS X: Pre-emptive Multitasking and Protected Memory. Mac OS X: Symmetric Multiprocessing Components of Mac OS X The Layered Approach Darwin Core Services Graphics Services Application Environments Aqua Useful Mac OS X Jargon Bundles Frameworks Umbrella Frameworks Mac OS X Installation Initialization Options Installation Options Version 1.0 Copyright © 2001 by Apple Computer, Inc. All Rights Reserved. 1 Startup Keys Mac OS X Setup Assistant Mac OS 9 and Classic Standard Directory Names Quick Answers: Where do my __________ go? More Directory Names A Word on Paths Security UNIX and security Multiple user implementation Root Old Stuff in New Terms INITs in Mac OS X Fonts FKEYs Printing from Mac OS X Disk First Aid and Drive Setup Startup Items Mac OS 9 Control Panels and Functionality mapped to Mac OS X New Stuff to Check Out Review Questions Review Answers Further Reading Change history: 3/19/01: Removed comment about UFS volumes not being selectable by Startup Disk. -
HP Decset for Openvms Guide to the Module Management System
HP DECset for OpenVMS Guide to the Module Management System Order Number: AA–P119J–TE July 2005 This guide describes the Module Management System (MMS) and explains how to get started using its basic features. Revision/Update Information: This is a revised manual. Operating System Version: OpenVMS I64 Version 8.2 OpenVMS Alpha Version 7.3–2 or 8.2 OpenVMS VAX Version 7.3 Windowing System Version: DECwindows Motif for OpenVMS I64 Version 1.5 DECwindows Motif for OpenVMS Alpha Version 1.3–1 or 1.5 DECwindows Motif for OpenVMS VAX Version 1.2–6 Software Version: HP DECset Version 12.7 for OpenVMS Hewlett-Packard Company Palo Alto, California © Copyright 2005 Hewlett-Packard Development Company, L.P. Confidential computer software. Valid license from HP required for possession, use or copying. Consistent with FAR 12.211 and 12.212, Commercial Computer Software, Computer Software Documentation, and Technical Data for Commercial Items are licensed to the U.S. Government under vendor’s standard commercial license. The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein. Intel and Itanium are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries. Java is a US trademark of Sun Microsystems, Inc. Microsoft, Windows, and Windows NT are U.S. registered trademarks of Microsoft Corporation. -
Unit V Algorithm for Booting the UNIX System
Unit V Algorithm for booting the UNIX system : As we’ve noted, the boot process begins when the instructions stored in the computer’s permanent, nonvolatile memory (referred to colloquially as the BIOS, ROM,NVRAM, and so on) are executed. This storage location for the initial boot instructions is generically referred to as firmware (in contrast to “software,” but reflecting the fact that the instructions constitute a program[2]). These instructions are executed automatically when the power is turned on or the system is reset, although the exact sequence of events may vary according to the values of stored parameters.[3] The firmware instructions may also begin executing in response to a command entered on the system console (as we’ll see in a bit). However they are initiated, these instructions are used to locate and start up the system’s boot program , which in turn starts the Unix operating system. The boot program is stored in a standard location on a bootable device. For a normal boot from disk, for example, the boot program might be located in block 0 of the root disk or, less commonly, in a special partition on the root disk. In the same way, the boot program may be the second file on a bootable tape or in a designated location on a remote file server in the case of a network boot of a diskless workstation. There is usually more than one bootable device on a system. The firmware program may include logic for selecting the device to boot from, often in the form of a list of potential devices to examine. -
Linux-Kernel
linux-kernel #linux- kernel Table of Contents About 1 Chapter 1: Getting started with linux-kernel 2 Remarks 2 Versions 2 Examples 2 Installation or Setup 2 Download extract and enter to the kernel directory 2 Build the dependencies, compile the kernel and modules. 3 Chapter 2: Creation and usage of Kernel Threads 4 Introduction 4 Examples 4 Creation of kernel threads 4 Chapter 3: Event Tracing 6 Examples 6 Tracing I2C Events 6 Chapter 4: Fork System call 7 Examples 7 fork() system call 7 Chapter 5: How to find the right person for help. 9 Introduction 9 Examples 9 Find the "likely" maintainers for the FTDI USB serial converter 9 Chapter 6: Linux Hello World Device driver 10 Examples 10 An empty kernel module 10 Building and running the module 10 Chapter 7: Linux: Named Pipes(FIFO) 12 Examples 12 What is Named Pipe (FIFO) 12 Credits 13 About You can share this PDF with anyone you feel could benefit from it, downloaded the latest version from: linux-kernel It is an unofficial and free linux-kernel ebook created for educational purposes. All the content is extracted from Stack Overflow Documentation, which is written by many hardworking individuals at Stack Overflow. It is neither affiliated with Stack Overflow nor official linux-kernel. The content is released under Creative Commons BY-SA, and the list of contributors to each chapter are provided in the credits section at the end of this book. Images may be copyright of their respective owners unless otherwise specified. All trademarks and registered trademarks are the property of their respective company owners. -
The Big Picture So Far Today: Process Management
The Big Picture So Far From the Architecture to the OS to the User: Architectural resources, OS management, and User Abstractions. Hardware abstraction Example OS Services User abstraction Processor Process management, Scheduling, Traps, Process protection, accounting, synchronization Memory Management, Protection, virtual memory Address spaces I/O devices Concurrency with CPU, Interrupt Terminal, mouse, printer, handling system calls File System File management, Persistence Files Distributed systems Networking, security, distributed file Remote procedure calls, system network file system System calls Four architectures for designing OS kernels Computer Science CS377: Operating Systems Lecture 4, page 1 Today: Process Management • A process as the unit of execution. • How are processes represented in the OS? • What are possible execution states and how does the system move from one state to another? • How are processes created in the system? • How do processes communicate? Is this efficient? Computer Science CS377: Operating Systems Lecture 4, page 2 What's in a Process? • Process: dynamic execution context of an executing program • Several processes may run the same program, but each is a distinct process with its own state (e.g., MS Word). • A process executes sequentially, one instruction at a time • Process state consists of at least: ! the code for the running program, ! the static data for the running program, ! space for dynamic data (the heap), the heap pointer (HP), ! the Program Counter (PC), indicating the next instruction, ! an execution stack with the program's call chain (the stack), the stack pointer (SP) ! values of CPU registers ! a set of OS resources in use (e.g., open files) ! process execution state (ready, running, etc.). -
Processes and Job Control
Processes and Job Control Hour 17 PObjectives < Definitions: process, orphan, and zombie < System processes < Process creation < Examining processes: the ps command < Job control: &, nohup, fg, bg, jobs, ( ), and kill < Exit status Copyright © 1998-2002 Delroy A. Brinkerhoff. All Rights Reserved. Hour 17 Unix Slide 1 of 12 Process Also called a job by C and Korn shells PWhen a program or executable file is loaded from disk and started running (i.e., when a command is run), it is called a process vi pid 641 < identified by a unique process ID (PID) number < has an owner vi < private data vi PA program can be loaded more than once pid 895 < creates multiple processes vi < each process has a different PID < each process may have a different owner PPIDs are unique, nonnegative integers < numbers recycle without collisions Hour 17 Unix Slide 2 of 12 System Processes Processes created during system boot P0System kernel < “hand crafted” at boot < called swap in older versions (swaps the CPU between processes) < called sched in newer versions (schedules processes) < creates process 1 P1 init (the parent of all processes except process 0) < general process spawner < begins building locale-related environment < sets or changes the system run-level P2 page daemon (pageout on most systems) P3 file system flusher (fsflush) Hour 17 Unix Slide 3 of 12 Process Life Cycle Overview of creating new processes fork init init pid 467 Pfork creates two identical pid 1 exec processes (parent and child) getty pid 467 Pexec < replaces the process’s instructions -
6.087 Practical Programming in C, Lecture 14
Outline Review Inter process communication Signals Fork Pipes FIFO Spotlights 1 6.087 Lecture 14 – January 29, 2010 Review Inter process communication Signals Fork Pipes FIFO Spotlights 2 Review: multithreading • Race conditions • non-determinism in thread order. • can be prevented by synchronization • atomic operations necessary for synchronization • Mutex: Allows a single thread to own it • Semaphores: Generalization of mutex, allows N threads to acquire it at a time. • P(s) : acquires a lock • V(s) : releases lock • sem_init(),sem_destroy() • sem_wait(),sem_trywait(),sem_post() • Other problems: deadlock, starvation 2 Sockets • <sys/socket.h> • enables client-server computing • Client: connect() • Server: bind(),listen(),accept() • I/O: write(),send(),read(),recv() 3 6.087 Lecture 14 – January 29, 2010 Review Inter process communication Signals Fork Pipes FIFO Spotlights 4 Preliminaries • Each process has its own address space. Therefore, individual processes cannot communicate unlike threads. • Interprocess communication: Linux/Unix provides several ways to allow communications • signal • pipes • FIFO queues • shared memory • semaphores • sockets 4 <signals.h> • Unix/Linux allows us to handle exceptions that arise during execution (e.g., interrupt, floating point error, segmentation fault etc.). • A process recieves a signal when such a condition occurs. void (∗signal(int sig,void(∗handler)(int )))( int ) • determines how subsequent signals will be handled. • pre-defined behavior: SIG_DFL (default), SIG_IGN (ignore) • returns the previous handler. 5 <signal.h> Valid signals: SIGABRT abnormal termination SIGFPE floating point error SIGILL illegal instruction SIGINT interrupt SIGSEGV segmentation fault SIGTERM termination request SIGBUS bus error SIGQUIT quit The two signals SIGSTOP,SIGKILL cannot be handled. 6 <signal.h> int raise( int sig) can be used to send signal sig to the program. -
Lecture 4: September 13 4.1 Process State
CMPSCI 377 Operating Systems Fall 2012 Lecture 4: September 13 Lecturer: Prashant Shenoy TA: Sean Barker & Demetre Lavigne 4.1 Process State 4.1.1 Process A process is a dynamic instance of a computer program that is being sequentially executed by a computer system that has the ability to run several computer programs concurrently. A computer program itself is just a passive collection of instructions, while a process is the actual execution of those instructions. Several processes may be associated with the same program; for example, opening up several windows of the same program typically means more than one process is being executed. The state of a process consists of - code for the running program (text segment), its static data, its heap and the heap pointer (HP) where dynamic data is kept, program counter (PC), stack and the stack pointer (SP), value of CPU registers, set of OS resources in use (list of open files etc.), and the current process execution state (new, ready, running etc.). Some state may be stored in registers, such as the program counter. 4.1.2 Process Execution States Processes go through various process states which determine how the process is handled by the operating system kernel. The specific implementations of these states vary in different operating systems, and the names of these states are not standardised, but the general high-level functionality is the same. When a process is first started/created, it is in new state. It needs to wait for the process scheduler (of the operating system) to set its status to "new" and load it into main memory from secondary storage device (such as a hard disk or a CD-ROM). -
Beyond Init: Systemd Linux Plumbers Conference 2010
Beyond Init: systemd Linux Plumbers Conference 2010 Kay Sievers Lennart Poettering November 2010 Kay Sievers, Lennart Poettering Beyond Init: systemd Triggers: Boot, Socket, Bus, Device, Path, Timers, More Kay Sievers, Lennart Poettering Beyond Init: systemd Kay Sievers, Lennart Poettering Beyond Init: systemd Substantial coverage of basic OS boot-up tasks, including fsck, mount, quota, hwclock, readahead, tmpfiles, random-seed, console, static module loading, early syslog, plymouth, shutdown, kexec, SELinux, initrd+initrd-less boots. Status: almost made Fedora 14. Kay Sievers, Lennart Poettering Beyond Init: systemd including fsck, mount, quota, hwclock, readahead, tmpfiles, random-seed, console, static module loading, early syslog, plymouth, shutdown, kexec, SELinux, initrd+initrd-less boots. Status: almost made Fedora 14. Substantial coverage of basic OS boot-up tasks, Kay Sievers, Lennart Poettering Beyond Init: systemd mount, quota, hwclock, readahead, tmpfiles, random-seed, console, static module loading, early syslog, plymouth, shutdown, kexec, SELinux, initrd+initrd-less boots. Status: almost made Fedora 14. Substantial coverage of basic OS boot-up tasks, including fsck, Kay Sievers, Lennart Poettering Beyond Init: systemd quota, hwclock, readahead, tmpfiles, random-seed, console, static module loading, early syslog, plymouth, shutdown, kexec, SELinux, initrd+initrd-less boots. Status: almost made Fedora 14. Substantial coverage of basic OS boot-up tasks, including fsck, mount, Kay Sievers, Lennart Poettering Beyond Init: systemd hwclock, readahead, tmpfiles, random-seed, console, static module loading, early syslog, plymouth, shutdown, kexec, SELinux, initrd+initrd-less boots. Status: almost made Fedora 14. Substantial coverage of basic OS boot-up tasks, including fsck, mount, quota, Kay Sievers, Lennart Poettering Beyond Init: systemd readahead, tmpfiles, random-seed, console, static module loading, early syslog, plymouth, shutdown, kexec, SELinux, initrd+initrd-less boots. -
Pid T Fork(Void); Description: Fork Creates a Child Process That Differs
pid_t fork(void); Description: fork creates a child process that differs from the parent process only in its PID and PPID, and in the fact that resource utilizations are set to 0. File locks and pending signals are not inherited. Returns: On success, the PID of the child process is returned in the parent's thread of execution, and a 0 is returned in the child's thread of execution. int execve(const char *filename, char *const argv [], char *const envp[]); Description: execve() executes the program pointed to by filename. filename must be either a binary executable, or a script. argv is an array of argument strings passed to the new program. envp is an array of strings, conventionally of the form key=value, which are passed as environment to the new program. Returns: execve() does not return on success, and the text, data, bss, and stack of the calling process are overwritten by that of the program loaded. pid_t wait(int *status); pid_t waitpid(pid_t pid, int *status, int options); Description: The wait function suspends execution of the current process until a child has exited, or until a signal is delivered whose action is to terminate the current process or to call a signal handling function. The waitpid function suspends execution of the current process until a child as specified by the pid argument has exited, or until a signal is delivered whose action is to terminate the current process or to call a signal handling function. If a child has already exited by the time of the call (a so-called \zombie" process), the function returns immediately.