Squashfs is a compressed read-only file system for

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

. Squashfs compresses files,

inode An inode (index node) is a data structure in a Unix-style file system that describes a file-system object such as a file or a directory. Each inode stores the attributes and disk block locations of the object's data. File-system object attribu ...

s and directories, and supports block sizes from 4 KiB up to 1 MiB for greater compression. Several compression algorithms are supported. Squashfs is also the name of

free software Free software, libre software, libreware sometimes known as freedom-respecting software is computer software distributed open-source license, under terms that allow users to run the software for any purpose as well as to study, change, distribut ...

, licensed under the GPL, for accessing Squashfs filesystems. Squashfs is intended for general read-only file-system use and in constrained block-device memory systems (e.g. embedded systems) where low overhead is needed.

Uses

Squashfs is used by the Live CD versions of Arch Linux, Clonezilla,

Debian Debian () is a free and open-source software, free and open source Linux distribution, developed by the Debian Project, which was established by Ian Murdock in August 1993. Debian is one of the oldest operating systems based on the Linux kerne ...

, Fedora,

Gentoo Linux Gentoo Linux (pronounced ) is a Linux distribution built using the Portage package management system. Unlike a binary software distribution, the source code is compiled locally according to the user's preferences and is often optimized for ...

, KDE neon, Kali Linux,

Linux Mint Linux Mint is a community-developed Linux distribution. It is based on Ubuntu and designed for x86-64 based computers; another variant is based on Debian which is named Linux Mint Debian Edition (LMDE) and has both 64-bit and IA-32 support. T ...

, NixOS, Salix,

Ubuntu Ubuntu ( ) is a Linux distribution based on Debian and composed primarily of free and open-source software. Developed by the British company Canonical (company), Canonical and a community of contributors under a Meritocracy, meritocratic gover ...

, openSUSE and on embedded distributions such as the

OpenWrt OpenWrt (from ''open wireless router'') is an open-source project for embedded operating systems based on Linux kernel, Linux, primarily used on Embedded system, embedded devices to Router (computing), route network traffic. The main components ...

and DD-WRT router

firmware In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, h ...

. It is also used in

Chromecast Chromecast is a discontinued line of digital media players developed by Google. The devices, designed as small dongles, can play Internet-streaming media, streamed audio-visual content on a high-definition television or home audio system. The u ...

, in Tiny Core Linux fo
packaging extensions
and for the system partitions of some Android releases ( Android Nougat). It is often combined with a union mount filesystem, such as UnionFS, OverlayFS, or aufs, to provide a read-write environment for live Linux distributions. This takes advantage of both Squashfs's high-speed compression abilities and the ability to alter the distribution while running it from a live CD. Distributions such as Debian Live, Mandriva One, Puppy Linux, Salix Live and Slax use this combination. The AppImage project, which aims to create portable Linux applications, uses Squashfs for creating AppImages. The snap package system also uses Squashfs as its file container format. Squashfs is also used by Linux Terminal Server Project and Splashtop. The tools ''unsquashfs'' and ''mksquashfs'' have been ported to

Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...

– Windows 8.1. 7-Zip also supports Squashfs.

History

Squashfs was initially maintained as an out-of-tree Linux patch. The initial version 1.0 was released on 23 October 2002. In 2009 Squashfs was merged into Linux mainline as part of Linux 2.6.29. In that process, the backward-compatibility code for older formats was removed. Since then the Squashfs kernel-space code has been maintained in the Linux mainline tree, while the user-space tools remain on the project's

GitHub GitHub () is a Proprietary software, proprietary developer platform that allows developers to create, store, manage, and share their code. It uses Git to provide distributed version control and GitHub itself provides access control, bug trackin ...

page. The original version of Squashfs used gzip compression, although Linux kernel 2.6.34 added support for LZMA and LZO compression, Linux kernel 2.6.38 added support for LZMA2 compression (which is used by xz), Linux kernel 3.19 added support for LZ4 compression, and Linux kernel 4.14 added support for Zstandard compression. Linux kernel 2.6.35 added support for extended file attributes.

References

External links

*

{{File systems Compression file systems Free special-purpose file systems Read-only file systems supported by the Linux kernel Free software programmed in C

Uses

History

See also

References

External links