What is a disk image? | View definition and learn about file formats and applications

A disk image refers to the process of copying and transferring the contents of a data storage device or medium to another similar medium or device. In its original context, disk imaging means creating an exact replica of a computer hard drive, including the programs, settings, and data within specific compression file formats contained on it.

The purpose of a disk image is to provide the user with a replica of a computer system and its data. This way, in case of a catastrophic hard drive failure or when the user needs to restore a system or data (e.g., after a virus attack or accidental event), these replicas can be used. Additionally, a system's setup can be "cloned" to install on another computer or migrated to another hard drive.

What are disk images used for?

Disk imaging is used to copy optical media, such as DVDs and Blu-rays. It's also used to clone a hard drive in its entirety, as mentioned above. Disk images are often used as backup files. But they're also related to virtual disks.

A virtual disk can emulate any type of physical drive, such as a hard drive, tape drive, floppy disk drive, CD/DVD/BD/HD-DVD, or a network share; naturally, a virtual drive requires a virtual reading device to match. The emulated drive is typically created in RAM (called a RAM disk) or on a hard drive for faster read-write access. Typical uses for a virtual disk include mounting disc images and mounting a virtual hard drive for “on-the-fly encryption” (OTFE).

A virtual disk is usually read-only and used to mount existing images that cannot be modified. However, some software offers virtual CD/DVD drives that can create new images; such a virtual disk is called a “virtual writer” (or by another name).

Disk image applications

Disk images are typically used in two major areas: system backups and software distribution/deployment. Let's examine the advantages of disk images in these contexts:

【System Backup】:

While some backup software only saves user files, system boot information and files locked by the operating system (for example, files in use during the backup) may not be saved. A disk image contains all the files and duplicates all data, including file attributes and fragmentation status. This means you can use it to back up an operating system and perform an accurate and efficient single-image system restore after making changes to the system or a virtual machine.

Software distribution/deployment:

If you are in charge of IT for a medium-sized business, you can use images to distribute software over your network, or to make it portable. With software distributed via images, you can download and install programs on many networked machines with no disruption to users, and even schedule updates for off-peak hours.

How to Create a Disk Image

Disk imaging software is mainly used for quickly and conveniently backing up computer programs and data stored on a hard drive. While most people think of it in terms of data backup, disk imaging software also backs up a computer's system settings.

In effect, disk-imaging software takes a “snapshot” of a computer system – its architecture, registry, tweaks, software, and so on. This can be invaluable if something goes wrong with the system: for example, if it is hit by a malicious virus that requires the hard drive to be reformatted or wiped; if a software or hardware glitch necessitates a reset; or if a human disaster or accident (such as fire or flood) occurs.

In other words, the clone is a disk image that contains the latest “rescue” image, allowing one to return rapidly to the cloned state, without having to reinstall software or reset and configure settings to the desired configuration.

Another use for disk-imaging software is for system administrators who manage many similarly configured computers. Instead of spending time transferring and configuring systems on different machines, they can easily and quickly copy a system from one machine and “install” the disk image on another.

Disk imaging software

The most popular disk-imaging program is Symantec's Ghost, which can duplicate an entire hard drive (even if it is only half full) in its early versions, and, in later ones, copy either an entire drive or a single partition. Ghost also offers several options for replicating systems or data: directly to another hard drive on the same machine; across a network or a parallel cable to another computer; or to a network or tape drive.

The enterprise version of Ghost supports multicasting, which allows an image to be sent simultaneously to multiple computers from one source, thus relieving network congestion that would result from transmitting large files (typically many tens or hundreds of megabytes) to each machine individually.

Best Disk Imaging Software - Todo Backup Tools

Todo Backup is a reliable disk imaging software that provides secure backup and recovery solutions, including one-click system, file, and application backup.

Step 1: Launch Todo Backup and click "Create Backup" on the main interface, then click the big question mark to select backup content.

2. To back up your Windows operating system, click Operating System to begin the backup.

Step 3: System information and all system-related files and partitions will be selected automatically; you don't need to make any manual selections. Next, click on the area highlighted in the screenshot below to choose a location to save your system image backup.

**Step 4.** You can choose another local drive on your computer, an external hard drive, a network, cloud storage, or Network Attached Storage (NAS) as the backup location. Generally, we recommend using a physical external drive or the cloud to save your system image files.

5. If you're interested, you can customize settings like automatic daily, weekly, or monthly backups, and differential or incremental backups. Click "Options," then click "Backup Now" to begin the Windows backup process. When it's finished, the backup will appear as a card on the left side.

The format of the disk image

Since all operating systems support the creation and running of disk images, these images come in different formats. For example, disk images created with tools like Todo Backup have the file extension .pbd. Here, we'll list some common disk image formats:

Here is a list of file formats: 1. Apple Disk Image (.dmg) - An installable image file format used for Mac OS 2. IMG - Typically used for disk imaging, a generic image file format 3. VHD - Virtual Hard Disk file format, commonly found in virtualization platforms like Microsoft's Hyper-V and VirtualBox 4. VDI - Virtual Machine Disk file format, utilized by Oracle's VirtualBox and VMware 5. VMDK - Virtual Machine Disk Image file format, widely used in VMware products 6. QCOW - QEMU Copy-On-Write, a lightweight disk image file format mainly used with QEMU virtual machines in Linux-based virtualization environments Please note that the choice of format depends on your specific requirements, such as the operating system, virtualization software, or cloud platform.