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29-403: A disk image with a copy of macOS , macOS Server , Mac OS 9 , or Mac OS 8 is created using System Image Utility and is stored on a server, typically macOS Server. Clients receive this image across a network using many popular protocols including: HTTPS , AFP , TFTP , NFS , and multicast Apple Software Restore (ASR). Server-side NetBoot image can boot entire machines, although NetBoot

58-577: A CD/DVD drive by reading an ISO image . This can also be faster than reading from the physical optical medium. Further, there are less issues with wear and tear. A hard disk drive or solid-state drive in a virtual machine is implemented as a disk image (i.e. either the VHD format used by Microsoft's Hyper-V , the VDI format used by Oracle Corporation 's VirtualBox , the VMDK format used for VMware virtual machines, or

87-508: A TFTP transfer of the Mac OS ROM file . Next, two volumes are mounted via AppleTalk over TCP on which the client disk images reside. All in all, the Classic Mac OS uses three images; a System image which contains the operating system and may contain applications. Next a private image (or scratch disk) is mounted in an overlay over the read-only System image. Finally, an applications image

116-406: A bit-by-bit copy to ensure forensic soundness. The purposes of imaging the disk is to not only discover evidence preserved in digital information but also to examine the drive to gather clues of how the crime was committed. Creating a virtual disk image of optical media or a hard disk drive is typically done to make the content available to one or more virtual machines . Virtual machines emulate

145-533: A computer. This is usually used in conjunction with a DHCP server to automate the configuration of network parameters including IP addresses. Multicasting , broadcasting or unicasting tend to be used to restore an image to many computers simultaneously. These approaches do not work well if one or more computers experience packet loss. As a result, some imaging solutions use the BitTorrent protocol to overcome this problem. Network-based image deployment reduces

174-421: A raw disk image is always a multiple of the sector size. For floppy disks and hard drives this size is typically 512 bytes (but other sizes such as 128 and 1024 exist). More precisely, the file size of a raw disk image of a magnetic disk corresponds to: E.g. for 80 cylinders (tracks) and 2 heads (sides) with 18 sectors per track: For optical discs such as CDs and DVDs, the raw sector size is usually 2,352, making

203-435: A single disk. In some cases, disk imaging can fail due to bad sectors or physical wear and tear on the source device. Unix utilities (such as dd ) are not designed to cope with failures, causing the disk image creation process to fail. When data recovery is the end goal, it is instead recommended to use more specialised tools (such as ddrescue ). IMG (file format) IMG , in computing, refers to binary files with

232-644: A virtual disk image. A virtual burner, by definition, appears as a disc drive in the system with writing capabilities (as opposed to conventional disc authoring programs that can create virtual disk images), thus allowing software that can burn discs to create virtual discs. Forensic imaging is the process of creating a bit-by-bit copy of the data on the drive, including files, metadata, volume information, filesystems and their structure. Often, these images are also hashed to verify their integrity and that they have not been altered since being created. Unlike disk imaging for other purposes, digital forensic applications take

261-598: Is a similar feature of macOS Server which utilizes NetBoot and ASR to deliver installation images to network clients (typically on first boot). Like NetBoot, NetInstall images can be created using the System Image Utility . NetInstall performs a function for macOS similar to Windows Deployment Services for Microsoft clients, which depend on the Preboot Execution Environment. Mac OS 8.5 and Mac OS 9 use only BOOTP/DHCP to get IP information, followed by

290-414: Is more commonly used for operating system and software deployment , somewhat similar to Norton Ghost . Client machines first request network configuration information through DHCP , then a list of boot images and servers with BSDP and then proceed to download images with protocols mentioned above. Both Intel and PowerPC -based servers can serve images for Intel and PowerPC-based clients. NetInstall

319-482: Is mounted. This image, however, may be empty. Disk image A disk image is a snapshot of a storage device's structure and data typically stored in one or more computer files on another storage device. Traditionally, disk images were bit-by-bit copies of every sector on a hard disk often created for digital forensic purposes, but it is now common to only copy allocated data to reduce storage space. Compression and deduplication are commonly used to reduce

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348-453: Is used to create an image of a completely-configured system (such an image is sometimes called a golden image). This image is then written to a computer's hard disk (which is sometimes described as restoring an image). Image restoration can be done using network-based image deployment. This method uses a PXE server to boot an operating system over a computer network that contains the necessary components to image or restore storage media in

377-484: Is usually simpler to program than accessing a real floppy drive (particularly if the disks are in a format not supported by the host operating system), and allows a large library of software to be managed. Emulation also allows existing disk images to be put into a usable form even though the data contained in the image is no longer readable without emulation. Disk imaging is time consuming, the space requirements are high and reading from them can be slower than reading from

406-424: The .img filename extension that store raw disk images of floppy disks , hard drives , and optical discs or a bitmap image – .img . The .img filename extension is used by disk image files, which contain raw dumps of a magnetic disk or of an optical disc . Since a raw image consists of a sector -by-sector binary copy of the source medium, the actual format of the file contents will depend on

435-461: The .img file extension for raw images of hard drive disks, calling the format simply "raw". CloneCD stores optical disc images in .img files and generates additional CloneCD Control Files (with .ccd extension) for each image to hold the necessary metadata . The CUE/BIN format stores disc images in .bin files, which are functionally equivalent to .img image files, and uses .cue files as descriptor files. The file size of

464-502: The QCOW format used by QEMU ). Virtual hard disk images tend to be stored as either a collection of files (where each one is typically 2GB in size), or as a single file. Virtual machines treat the image set as a physical drive. Educational institutions and businesses can often need to buy or replace computer systems in large numbers. Disk imaging is commonly used to rapidly deploy the same configuration across workstations. Disk imaging software

493-479: The dd program can be used to create raw disk images. Apple Disk Copy can be used on Classic Mac OS and macOS systems to create and write disk image files. Authoring software for CDs/DVDs such as Nero Burning ROM can generate and load disk images for optical media. A virtual disk writer or virtual burner is a computer program that emulates an actual disc authoring device such as a CD writer or DVD writer. Instead of writing data to an actual disc, it creates

522-483: The file system of the disk from which the image was created (such as a version of FAT ). Raw disk images of optical media (such as CDs and DVDs ) contain a raw image of all the tracks in a disc (which can include audio, data and video tracks). In the case of CD-ROMs and DVDs, these images usually include not only the data from each sector, but the control headers and error correction fields for each sector as well. Since IMG files hold no additional data beyond

551-533: The benefits of disk imaging the storage costs can be high, management can be difficult and they can be time consuming to create. Disk images were originally (in the late 1960s) used for backup and disk cloning of mainframe disk media. Early ones were as small as 5 megabytes and as large as 330 megabytes, and the copy medium was magnetic tape , which ran as large as 200 megabytes per reel. Disk images became much more popular when floppy disk media became popular, where replication or storage of an exact structure

580-484: The control headers and error correction fields of CD-ROM or DVD sectors that raw disc images usually store. Their internal format follows the structure of an optical disc file system, commonly ISO 9660 (for CDs) or UDF (for DVDs). The CUE/BIN and CCD/IMG formats, which usually contain raw disc images, can also store ISO images instead. .img is also a planar bitmap graphics file using simple run-length encoding, originating with Digital Research 's GEM . It

609-434: The disk contents, these files can only be automatically handled by programs that can detect their file systems . For instance, a typical raw disk image of a floppy disk begins with a FAT boot sector , which can be used to identify its file system. Disc images of optical media are usually accompanied by a descriptor file which describes the layout of the disc, and includes information such as track limits which are not stored in

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638-630: The disk directly because of a performance overhead. Other limitations can be the lack of access to software required to read the contents of the image. For example, prior to Windows 8, third party software was required to mount disk images. When imaging multiple computers with only minor differences, much data is duplicated unnecessarily, wasting space. Disk imaging can be slow, especially for older storage devices. A typical 4.7 GB DVD can take an average of 18 minutes to duplicate. Floppy disks read and write much slower than hard disks. Therefore, despite their small size, it can take several minutes to copy

667-446: The exact and efficient recovery after experimenting with modifications to a system or virtual machine . Typically, disk imaging can be used to quickly restore an entire system to an operational state after a disaster. Libraries and museums are typically required to archive and digitally preserve information without altering it in any manner. Emulators frequently use disk images to emulate floppy disks that have been preserved. This

696-416: The need to maintain and update individual systems manually. Imaging is also easier than automated setup methods because an administrator does not need to have knowledge of the prior configuration to copy it. A disk image contains all files and data (i.e., file attributes and the file fragmentation state). For this reason, it is also used for backing up optical media ( CDs and DVDs , etc.), and allows

725-442: The raw image file. The .img file extension was originally used for floppy disk raw disk images only. A similar file extension, .ima , is also used to refer to floppy disk image files by some programs. A variant of IMG, called IMZ, consists of a gzipped version of a raw floppy disk image. These files use the .imz file extension, and are commonly found in compressed images of floppy disks created by WinImage. QEMU uses

754-433: The size of a raw disc image a multiple of this value. ISO images are another type of optical disc image files, which commonly use the .iso file extension, but sometimes use the .img file extension as well. They are similar to the raw optical disc images, but contain only one track with computer data obtained from an optical disc. They cannot contain multiple tracks, nor audio or video tracks. They also do not contain

783-608: The size of the image file set. Disk imaging is done for a variety of purposes including digital forensics , cloud computing , system administration , as part of a backup strategy, and legacy emulation as part of a digital preservation strategy. Disk images can be made in a variety of formats depending on the purpose. Virtual disk images (such as VHD and VMDK) are intended to be used for cloud computing, ISO images are intended to emulate optical media and raw disk images are used for forensic purposes. Proprietary formats are typically used by disk imaging software. Despite

812-513: Was commonly used on the Atari ST line of home computers, but also with some GEM-based PC software such as Corel Ventura or Timeworks Publisher . In addition, .img is an Apple Disk Image used by the Mac OS X or macOS operating system. Garmin .img is a hard-disk image file format which contains a header and many subfiles and used to store the maps for its GPS units. The raw IMG file format

841-544: Was necessary and efficient, especially in the case of copy protected floppy disks. Disk image creation is called disk imaging and is often time consuming, even with a fast computer, because the entire disk must be copied. Typically, disk imaging requires a third party disk imaging program or backup software. The software required varies according to the type of disk image that needs to be created. For example, RawWrite and WinImage create floppy disk image files for MS-DOS and Microsoft Windows . In Unix or similar systems

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