In computing, a system image is a serialized copy of the entire state of a computer system stored in some non-volatile form, such as a file.
If a system has all its state written to a disk (i.e. on a disk image), then a system image can be produced by copying the disk to a file elsewhere, often with disk cloning applications. On many systems a complete system image cannot be created by a disk cloning program running within that system because information can be held outside of disks and volatile memory, for example in non-volatile memory like boot ROMs.
A system is said to be capable of using system images if it can be shut down and later restored to exactly the same state. In such cases, system images can be used for backup.
Hibernation is an example that uses an image of the entire machine's RAM.
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Using a System Image to Restore an HP Computer in Windows 8
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Transcription
This video shows how to restore your computer using a system image in Windows 8. A system image is a file containing a snapshot of all of the data on a hard drive at any given time. If your hard drive fails or is corrupt, you can restore your files and settings to the point when you created the system image. To create a system image, you will need a storage device such as an external hard drive or DVDs. For this example we will use an external hard drive. From the Start Screen, press the Windows and W keys to search in Settings. Begin typing File Recovery, and select Windows 7 File Recovery from the list of results. Click Create a system image. Choose the storage device you would like to use, and then click Next. Select the drives you want to include in the image, and then click Next. Make sure that you have enough blank space on your storage device to create the system image. Confirm the settings, and then click Start backup. Continue to follow the on-screen instructions until the image is complete. Processing time will vary based on how much data you are backing up. Don’t disrupt the process even if it takes over an hour to complete. When the system image has been created, you will be asked to create a system repair disc that can be used to boot the computer in case of startup problems. It is not necessary to create the repair disc to complete the system image process. If you would like to create a repair disc, click Yes and follow the onscreen instructions. If you have already created a system repair disc or do not want to create one now, click No to proceed. The system image has been created. Click Close. Connect the storage device containing the system image to the computer. From the Startup screen, click Settings, then select the Power button. While holding down the shift key, click Restart to reboot the computer to open the Advanced Startup menu. When the computer restarts to the Advanced Startup Menu, click Troubleshoot, and then select Advanced options. Click System Image Recovery. Enter the user account and password, and then click Continue. Select Use the latest available system image, and then click Next. Click Next. Click Finish, and then click Yes. Windows begins to restore the computer. Follow the on-screen instructions to completely restore the computer. Processing time varies and could take up to a few hours to complete. Do not interrupt the process. When the system image is restored, your computer automatically restarts. Thank you for viewing this video. For more help, go to hp.com/support.
Process images
A process image is a copy of a given process's state at a given point in time. It is often used to create persistence within an otherwise volatile system. A common example is a database management system (DBMS). Most DBMS can store the state of its database or databases to a file before being closed down (see database dump). The DBMS can then be restarted later with the information in the database intact and proceed as though the software had never stopped. Another example would be the hibernate feature of many operating systems. Here, the state of all RAM memory is stored to disk, the computer is brought into an energy saving mode, then later restored to normal operation.
Some emulators provide a facility to save an image of the system being emulated. In video gaming this is often referred to as a savestate.
Another use is code mobility: a mobile agent can migrate between machines by having its state saved, then copying the data to another machine and restarting there.
Programming language support
Some programming languages provide a command to take a system image of a program. This is normally a standard feature in Smalltalk (inspired by FLEX) and Lisp, among other languages. Development in these languages is often quite different from many other programming languages. For example, in Lisp the programmer may load packages or other code into a running Lisp implementation using the read-eval-print loop, which usually compiles the programs. Data is loaded into the running Lisp system. The programmer may then dump a system image, containing that pre-compiled and possibly customized code—and also all loaded application data. Often this image is an executable, and can be run on other machines. This system image can be the form in which executable programs are distributed—this method has often been used by programs (such as TeX and Emacs) largely implemented in Lisp, Smalltalk, or idiosyncratic languages to avoid spending time repeating the same initialization work every time they start up.
Similar, Lisp Machines were booted from Lisp images, called Worlds. The World contains the complete operating system, its applications and its data in a single file. It was also possible to save incremental Worlds, that contain only the changes from some base World. Before saving the World, the Lisp Machine operating system could optimize the contents of memory (better memory layout, compacting data structures, sorting data, ...).
Although its purpose is different, a "system image" is often similar in structure to a core dump.
See also
External links
This page was last edited on 23 April 2024, at 03:15