![]() ![]() ![]() Disk image - Wikipedia"CD image" redirects here. For ISO 9. 66. 0 image files, see ISO image. A disk image, in computing, is a computer file containing the contents and structure of a disk volume or of an entire data storage device, such as a hard disk drive, tape drive, floppy disk, optical disc or USB flash drive. A disk image is usually made by creating a sector- by- sector copy of the source medium, thereby perfectly replicating the structure and contents of a storage device independent of the file system. Depending on the disk image format, a disk image may span one or more computer files. The file format may be an open standard, such as the ISO image format for optical disc images, or a disk image may be unique to a particular software application. The size can be huge because it contains the contents of an entire disk. People are always telling you how to maximize your mornings, but your morning routine—whatever it may be—is fine. What you really need is an afternoon routine.I recently, after backing up my files on an external hard drive, did a system recovery due to a virus on my computer. My computer was up and running for about a week. Combine all cleaning and wiping tasks in different erasing procedures launched manually or at scheduled times or events (user log-on/log-off, system start-up/shutdown. To reduce storage requirements, if an imaging utility is filesystem- aware it can omit copying unused space, and it can compress the used space. History[edit]Disk images were originally (in the late 1. Disk images became much more popular when floppy disk media became popular, where replication or storage of an exact structure was necessary and efficient, especially in the case of copy protected floppy disks. Disk images are used heavily for duplication of optical media including DVDs, Blu- ray disks, etc. It is also used to make perfect clones of hard disks. A virtual disk may emulate any type of physical drive, such as a hard disk drive, tape drive, key drive, floppy drive, CD/DVD/BD/HD DVD or a network share among others; and of course, since it is not physical, requires a virtual reader device matched to it (see below). An emulated drive is typically created either in RAM for fast read/write access (known as a RAM disk), or on a hard drive. Typical uses of virtual drives include the mounting of disk images of CDs and DVDs, and the mounting of virtual hard disks for the purpose of on the fly disk encryption ("OTFE"). Some operating systems such as Linux[2] and mac. OS[3] have virtual drive functionality built- in (such as the loop device), while others such as older versions of Microsoft Windows require additional software. Starting from Windows 8, Windows includes native virtual drive functionality.[4][5]Virtual drives are typically read- only, being used to mount existing disk images which are not modifiable by the drive. However some software provides virtual CD/DVD drives which can produce new disk images; this type of virtual drive goes by a variety of names, including "virtual burner". Enhancement[edit]Using disk images in a virtual drive allows users to shift data between technologies, for example from CD optical drive to hard disk drive. This may provide advantages such as speed and noise (hard disk drives are typically four or five times faster than optical drives,< ref> pcguide. Access Time< /ref> quieter, suffer from less wear and tear, and in the case of solid- state drives, immune to some physical trauma). In addition it may reduce power consumption, since it may allow just one device (a hard disk) to be used instead of two (hard disk plus optical drive). Virtual drives may also be used as part of emulation of an entire machine (a virtual machine). Software distribution[edit]Since the spread of broadband, CD and DVD images have become a common medium for Linux distributions.[2] Applications for mac. OS are often delivered online as an Apple Disk Image containing a file system that includes the application, documentation for the application, and so on. Online data and bootable recovery CD images are provided for customers of certain commercial software companies. Disk images may also be used to distribute software across a company network, or for portability (many CD/DVD images can be stored on a hard disk drive). There are several types of software that allow software to be distributed to large numbers of networked machines with little or no disruption to the user. Some can even be scheduled to update only at night so that machines are not disturbed during business hours. These technologies reduce end- user impact and greatly reduce the time and man- power needed to ensure a secure corporate environment.[6] Efficiency is also increased because there is much less opportunity for human error. Disk images may also be needed to transfer software to machines without a compatible physical disk drive. For computers running mac. OS, disk images are the most common file type used for softwaredownloads, typically downloaded with a web browser. The images are typically compressed Apple Disk Image (. They are usually opened by directly mounting them without using a real disk. The advantage compared with some other technologies, such as Zip and RAR archives, is they do not need redundant drive space for the unarchived data. Software packages for Windows are also sometimes distributed as disk images including ISO images. While Windows versions prior to Windows 7 do not natively support mounting disk images to the files system, several software options are available to do this; see comparison of disc image software. Security[edit]Virtual hard disks are often used in on the fly disk encryption ("OTFE") software such as Free. OTFE and True. Crypt, where an encrypted "image" of a disk is stored on the computer. When the disk's password is entered, the disk image is "mounted", and made available as a new volume on the computer. Files written to this virtual drive are written to the encrypted image, and never stored in cleartext. The process of making a computer disk available for use is called "mounting", the process of removing it is called "dismounting" or "unmounting"; the same terms are used for making an encrypted disk available or unavailable. Virtualization[edit]A hard disk image is interpreted by a Virtual Machine Monitor as a system hard disk drive. IT administrators and software developers administer them through offline operations using built- in or third- party tools. In terms of naming, a hard disk image for a certain Virtual Machine monitor has a specific file type extension, e. VMware VMDK, . vhd for Xen and Microsoft Hyper- V, .Oracle VM Virtual. . Box, etc. Hard drive imaging is used in several major application areas: Forensic imaging or acquisition is the process where the entire drive contents are imaged to a file and checksum values are calculated to verify the integrity (in court cases) of the image file (often referred to as a "hash value"). Forensic images are acquired with the use of software tools. Some hardware cloning tools have added forensic functionality.)Drive cloning, as previously mentioned, is typically used to replicate the contents of the hard drive for use in another system. This can typically be done by software- only programs as it typically only requires the cloning of file structure and files themselves. Data recovery imaging (like forensic imaging) is the process of imaging every single sector on the source drive to another medium from which required files can be retrieved. In data recovery situations, one cannot rely on the integrity of the file structure and therefore a complete sector copy is mandatory (also similar to forensic imaging). The similarities to forensic imaging end there though. Forensic images are typically acquired using software tools such as En. Case and FTK. However, forensic imaging software tools have significantly limited ability to deal with drives that have hard errors (which is often the case in data recovery and why the drive was submitted for recovery in the first place). Data recovery imaging must have the ability to pre- configure drives by disabling certain attributes (such as SMART and G- List re- mapping) and the ability to work with unstable drives (drive instability/read instability can be caused by minute mechanical wear and other issues). Data recovery imaging must have the ability to read data from "bad sectors." Read instability is a major factor when working with drives in operating systems such as Windows. A typical operating system is limited in its ability to deal with drives that take a long time to read. For these reasons, software that relies on the BIOS and operating system to communicate with the hard drive is often unsuccessful in data recovery imaging; separate hardware control of the source hard drive is required to achieve the full spectrum of data recovery imaging.
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