unsquashfs

unsquashfs is a command-line utility used to extract the contents of a SquashFS filesystem image. It is part of the squashfs-tools package and is commonly available on Linux systems. SquashFS is a compressed, read-only filesystem; unsquashfs reads an image and reconstructs the file tree in a destination directory. It preserves file metadata such as permissions, ownership, and timestamps, and supports the compression formats used by SquashFS. By default, extracted content is placed into a directory named squashfs-root.

Usage is straightforward: the basic invocation is unsquashfs image.squashfs. To change the output location, use the -d option followed by a directory name, for example unsquashfs -d /tmp/extracted image.squashfs. Additional options allow selective extraction, handling of specific paths, and other behavior consistent with the version being used, reflecting features such as processing of hard links and special files.

Unsquashfs is commonly employed to inspect or modify the contents of live CDs, initramfs images, embedded systems, or other distributions that ship with SquashFS-based images. It is also useful in recovery and debugging workflows to access data within a compressed, read-only image without mounting it directly.

Limitations include that unsquashfs extracts to a writable directory and does not modify the image itself. To recreate a SquashFS image from an edited tree, a separate tool such as mksquashfs is used. Together, these tools facilitate viewing, editing, and repackaging SquashFS filesystem images.