mkdiskimage

mkdiskimage [options] <output_file> <size>[kMGT]

<output_file>
    The path and name of the disk image file to be created. This file will be overwritten if it already exists.

<size>[kMGT]
    The desired size of the disk image. The size can be specified in bytes (default), or with suffixes: 'k' for kilobytes, 'M' for megabytes, 'G' for gigabytes, or 'T' for terabytes (e.g., '10M' for 10 megabytes).

-v, --verbose
    Enables verbose output, showing more details about the image creation process.

-q, --quiet
    Suppresses all output except for critical errors, making the command run silently.

The mkdiskimage command is a utility designed to create a blank, unformatted disk image file. These image files are typically used as virtual disks for virtual machines, bootable media (like floppy or USB drives), or in embedded system development environments. While its functionality can often be replicated using standard Linux tools like dd, mkdiskimage often serves as a convenient wrapper or a component within specific build systems to streamline the process of allocating space for a disk image before it's formatted with a filesystem. It's particularly useful when a precisely sized raw image is needed as a precursor to creating FAT (File Allocation Table) filesystems using utilities such as mkfs.fat. The command provides a straightforward method to quickly generate an image file that can then be partitioned, formatted, and populated with data, simulating a physical disk.

mkdiskimage is not a standard, universally available command found in core Linux utility packages like util-linux or dosfstools on most modern distributions. Its presence and exact behavior vary significantly. It is often a custom shell script implemented within specific projects (e.g., for embedded systems or legacy boot environments) or part of older, less common toolchains. Users should verify its availability and specific syntax on their system. It typically creates a raw, unformatted image; subsequent formatting with tools like mkfs.fat is usually required.

A typical workflow involving mkdiskimage often follows these steps:
1. Create the image: mkdiskimage my_image.img 10M
2. Format with FAT: mkfs.fat my_image.img
3. Mount the image (optional): sudo losetup -f my_image.img followed by sudo mount /dev/loopX /mnt/my_image

Due to its non-standard nature, the mkdiskimage command can have different implementations. Some versions might directly integrate filesystem creation (e.g., calling mkfs.fat internally), while others might only create the raw file and leave formatting to the user. Always consult the documentation or source code for the specific mkdiskimage script or utility you are using.

The conceptual need for a mkdiskimage utility arose in scenarios requiring the creation of specific disk layouts, particularly for bootable media (like floppy disks or early hard disk images) for DOS/BIOS environments. While not a single, standardized command, scripts named mkdiskimage have been historically used in various projects to automate the process of creating a raw disk image file and sometimes immediately formatting it with a FAT filesystem. Its typical implementation leverages lower-level commands like dd for file allocation and mkfs.fat for formatting. Its prominence has waned with the shift away from physical bootable media and simple FAT-based bootloaders, but it remains relevant in niche areas such as embedded system development, emulation of legacy systems, and specialized build processes.

dd(1), mkfs.fat(8), losetup(8), fdisk(8), parted(8)