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Essential System Administration, 3rd Edition by Æleen Frisch

In computing , rebooting is the process by which a running computer system is restarted, either intentionally or unintentionally. Reboots can be either cold alternatively known as hard , in which the power to the system is physically turned off and back on again causing an initial boot of the machine, or warm or soft in which the system restarts without the need to interrupt the power.

The term restart is used to refer to a reboot when the operating system closes all programs and finalizes all pending input and output operations before initiating a soft reboot. Early electronic computers like the IBM had no operating system and little internal memory.

The input was often a stack of punch cards. The computer was initiated by pressing a start button that performed a single command - "read a card". This first card then instructed the machine to read more cards that eventually loaded a user program. This process was likened to an old saying, " picking yourself up by the bootstraps ", referring to a horseman who lifts himself off the ground by pulling on the straps of his boots.

This set of initiating punch cards was called "bootstrap cards". Thus a cold start was called booting the computer up. If the computer crashed , it was rebooted. The boot reference carried over to all subsequent types of computers. Technical sources describe two contrasting forms of reboot known as a cold reboot also a cold boot, hard reboot or hard boot and warm reboot also soft reboot, or soft boot , although the definition of these forms can vary slightly between sources.

According to Jones, Landes, and Tittel , [1] Cooper , [2] Tulloch [3] and Soper , [4] on IBM PC compatible platform, a cold boot is a boot process in which the computer starts from a powerless state. All except Tulloch also mention that in cold boot, the system performs a power-on self-test POST. In addition to the power switch , Cooper and Soper also state that the reset button , if present, may commence a cold reboot.

Jones, Landes, and Tittel contradicts this assertion and states that a reset button may commence either a cold or warm reboot, depending on the system. Microsoft Support article [5] states that although the reset button is designed to perform a cold reboot, it may not disconnect the power to the motherboard — a state that does not correspond to the cold boot definition given above.

According to Jones, Landes, and Tittel , : both the operating system and third-party software can initiate a cold boot; the restart command in Windows 9x initiates a cold reboot, unless Shift key is held. Finding a definition for warm boot, however, is more of a challenge. Jones, Landes, and Tittel specifies that for a warm reboot to occur, BIOS must be the recipient of the key combination.

The Windows NT family of operating systems also does the same and reserves the key combination for its own use. The Linux family of operating systems supports an alternative to warm boot; the Linux kernel has optional support for kexec , a system call which transfers execution to a new kernel and skips hardware or firmware reset.

The entire process occurs independently of the system firmware. The kernel being executed does not have to be a Linux kernel.

A warm boot discards program memory. A cold boot additionally discards storage memory also known as the "object store" , while a clean boot erases all forms of memory storage from the device. However, since these areas do not exist on all Windows CE devices, users are only concerned with two forms of reboot: one that resets the volatile memory and one that wipes the device clean and restores factory settings.

For example, for a Windows Mobile 5. A hard reboot means that the system is not shut down in an orderly manner, skipping file system synchronisation and other activities that would occur on an orderly shutdown. This can be achieved by either applying a reset , by cycling power, by issuing the halt -q command in most Unix-like systems, or by triggering a kernel panic.

The term "restart" is used by the Microsoft Windows and Linux families of operating systems to denote an operating system-assisted reboot. Unexpected loss of power for any reason including power outage , power supply failure or depletion of battery on a mobile device forces the system user to perform a cold boot once the power is restored.

Some BIOSes have an option to automatically boot the system after a power failure. Such crashes may occur due to a multitude of software and hardware problems, such as triple faults. They are generally symptomatic of an error in ring 0 that is not trapped by an error handler in an operating system or a hardware-triggered non-maskable interrupt. Systems may be configured to reboot automatically after a power failure, or a fatal system error or kernel panic.

The method by which this is done varies depending on whether the reboot can be handled via software or must be handled at the firmware or hardware level.

This option is enabled by default in some editions. The introduction of advanced power management allowed operating systems greater control of hardware power management features.

While hibernation also involves turning a system off then subsequently back on again, the operating system does not start from scratch, thereby differentiating this process from rebooting. A reboot may be simulated by software running on an operating system. For example: the Sysinternals BlueScreen utility, which is used for pranking; or some modes of the bsod XScreenSaver "hack", for entertainment albeit possibly concerning at first glance.

Malware may also simulate a reboot, and thereby deceive a computer user for some nefarious purpose. Microsoft App-V sequencing tool captures all the file system operations of an installer in order to create a virtualized software package for users.

From Wikipedia, the free encyclopedia. Process by which a computer system is restarted. For other uses, see Reboot disambiguation. Main article: Booting. For the attack called a "cold boot attack", see Cold boot attack. Main article: Hibernation computing. Que Publishing. Microsoft Press. Archived from the original on 21 February O'Reilly Media.

Microsoft Support. Retrieved 19 January Larry Osterman's WebLog. MSDN Blogs. Retrieved 15 March Retrieved 3 March Cengage Learning. Donahue, Gary A. Sebastopol : O'Reilly Media. How-To Geek. Microsoft Hardware Dev Center. Hidden categories: All articles with dead external links Articles with dead external links from April Articles with permanently dead external links Articles with short description Short description is different from Wikidata Use dmy dates from October Namespaces Article Talk.

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Show a Custom Message to Users Before Linux Server Shutdown

Booting and Shutting Down a System Overview. Shutting Down a System Tasks. Booting a System Tasks. Booting a System From the Network Tasks. Troubleshooting Booting a System Tasks.

Jump to navigation. Understanding the Linux boot and startup processes is important to being able to both configure Linux and to resolving startup issues. This article presents an overview of the bootup sequence using the GRUB2 bootloader and the startup sequence as performed by the systemd initialization system. In reality, there are two sequences of events that are required to boot a Linux computer and make it usable: boot and startup. The boot sequence starts when the computer is turned on, and is completed when the kernel is initialized and systemd is launched. The startup process then takes over and finishes the task of getting the Linux computer into an operational state.

From time to time, you will need to shut the system down. This is necessary for scheduled maintenance, running diagnostics, hardware changes or additions, and other administrative tasks. All users are notified that the system will be going down, preferably giving them some reasonable advance warning. All running processes are sent a signal telling them to terminate, allowing them time to exit gracefully, provided the program has made provisions to do so. Depending on the type of shutdown, the system moves to single-user mode, the processor is halted, or the system is rebooted. After taking these steps, the administrator can turn the power off, execute diagnostics, or perform other maintenance activities as appropriate.

Linux shutdown command


  1. Talbot A.

    09.04.2021 at 06:13

    Beyond the question of controlling the boot or shutdown process, the open a getty process for each virtual console (login prompt in text mode). getty opens tty​.

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  4. Tiochronunol

    14.04.2021 at 20:49

    In this section, we touch upon the startup and shutdown process on Linux. Please refer to the official RedHat documentation for details about the boot up process. And if you are so inclined, there is also a text-based interface to chkconfig.

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    16.04.2021 at 04:17

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