squashfstools

Squashfs-tools is a collection of user-space utilities for creating, inspecting, and extracting SquashFS images, a compressed read-only filesystem for Linux. It provides programs such as mksquashfs, which creates a SquashFS filesystem from a directory tree, and unsquashfs, which extracts the contents of an image. Additional tools allow listing, testing, and managing metadata. The suite is widely used for building compact root filesystems in embedded devices and live media.

SquashFS is a highly compressed, read-only filesystem designed for space efficiency and fast access. Widely adopted in embedded devices, live CDs, and container bases, SquashFS images are mounted as read-only in Linux. The user-space tools enable creation, extraction, and inspection of contents and attributes.

Key features include support for multiple compression algorithms such as gzip, lzma (xz), lzo, and newer formats like zstd; options to tune block size, ownership, and permissions; and the ability to preserve metadata, hard links, symlinks, and extended attributes. The tools create an image from a directory, or extract an image to a directory, and can list or verify contents.

In practice, squashfs-tools are common in embedded Linux builds, live ISO creation, and software distribution where compact, portable root filesystems are needed. The package is provided as squashfs-tools in many distributions (for example, Debian and Ubuntu) and is used from the command line to package or unpack SquashFS images.

The project is open source, with public repositories and ongoing development. Licenses vary by version and component, but the tools are generally released under free licenses compatible with Linux distributions.