How to use the command systemd-dissect (with examples)

Systemd-dissect is a command that allows users to introspect and interact with file system OS disk images, specifically Discoverable Disk Images (DDIs). It provides various functionalities to work with disk images such as showing general image information, mounting and unmounting images, listing files within an image, and attaching and detaching images to loopback block devices.

Use case 1: Show general image information about the OS image

Code:

systemd-dissect path/to/image.raw

Motivation: This use case is helpful when you want to gather general information about an OS image without mounting it. It provides insights into important details such as the size of the image, its offset, and the file system used.

Explanation:

• path/to/image.raw: Path to the OS image file.

Example output:

[General]
Size=214748364800
Offset=1048576
Filesystem=ext4

Use case 2: Mount an OS image

Code:

systemd-dissect --mount path/to/image.raw /mnt/image

Motivation: Mounting an OS image allows users to access the file system within the image, and perform operations like reading and modifying files. This can be useful for forensics analysis or when working with disk images in a controlled manner.

Explanation:

• --mount: Flag used to indicate that the image needs to be mounted.
• path/to/image.raw: Path to the OS image file.
• /mnt/image: Mount point where the image will be mounted.

Use case 3: Unmount an OS image

Code:

systemd-dissect --umount /mnt/image

Motivation: After performing tasks on a mounted image, it is necessary to unmount it properly to ensure data integrity and prevent any issues. This command allows users to unmount an image when it is no longer needed.

Explanation:

• --umount: Flag used to indicate that the image needs to be unmounted.
• /mnt/image: Mount point of the image to be unmounted.

Use case 4: List files in an image

Code:

systemd-dissect --list path/to/image.raw

Motivation: Sometimes it is necessary to inspect the contents of an OS image without mounting it. This use case allows users to list the files present in the image, providing an overview of its contents.

Explanation:

• --list: Flag used to indicate that the files within the image need to be listed.
• path/to/image.raw: Path to the OS image file.

Example output:

/
|-- bin
|   |-- ls
|   |-- cat
|-- etc
|   |-- passwd
|   |-- hosts
|-- usr
|   |-- lib
|   |   |-- libssl.so.1.1

Use case 5: Attach an OS image to an automatically allocated loopback block device and print its path

Code:

systemd-dissect --attach path/to/image.raw

Motivation: Attaching an OS image to a loopback block device allows users to access the image as if it were a physical disk. This is useful when the image needs to be treated as a device and accessed through device-specific operations.

Explanation:

• --attach: Flag used to indicate that the image needs to be attached to a loopback block device.
• path/to/image.raw: Path to the OS image file.

Example output:

/dev/loop0

Use case 6: Detach an OS image from a loopback block device

Code:

systemd-dissect --detach path/to/device

Motivation: When an OS image is attached to a loopback block device, detaching it is necessary to release the device and prevent any potential issues. This command allows users to detach an image from a loopback block device.

Explanation:

• --detach: Flag used to indicate that the image needs to be detached from a loopback block device.
• path/to/device: Path to the loopback block device.

Conclusion:

The systemd-dissect command provides a range of functionalities for working with file system OS disk images. Whether you need to gather general information, mount or unmount images, list files within an image, or attach and detach images from loopback block devices, systemd-dissect has you covered. By understanding and utilizing these use cases, you can efficiently interact with OS disk images to perform various tasks, such as forensics analysis or controlled disk image manipulation.