SquashFS
| Developer | Phillip Lougher, Robert Lougher |
|---|---|
| Introduced | 2009 (Linux 2.6.29) |
| Limits | |
| Max. file size | 16 EiB |
| Max. volume size | 16 EiB |
| Features | |
| Transparent compression | gzip LZMA LZO LZMA2 |
| Supported operating systems | Linux |
SquashFS is a compressed read-only file system for Linux. SquashFS compresses files, inodes and directories, and supports block sizes up to 1 MB for greater compression. SquashFS is also the name of free/open software, 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. The original version of SquashFS used gzip compression, although Linux kernel 2.6.34 added support for LZMA[1] and LZO compression,[2] and Linux kernel 2.6.38 added support for LZMA2 compression (which is used by xz).[3]
Linux kernel 2.6.35 added support for Extended file attributes.[4]
Contents |
Uses[edit]
SquashFS is used by the Live CD versions of Arch Linux, Debian, Fedora, Gentoo Linux, Salix, Ubuntu and on embedded distributions such as the OpenWrt[5] and DD-WRT router firmware. It is often combined with a union mount filesystem, such as UnionFS or aufs, to provide a read-write environment for live Linux distributions. This takes advantage of both the 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 on-disk format of SquashFS has stabilized enough that it has been merged into the 2.6.29 version of the Linux kernel.[6] In that process, the backward-compatibility code for older formats was removed.
SquashFS is also used by Linux Terminal Server Project, Slax, and Splashtop. The tools unsquashfs and mksquashfs have been ported to Windows NT;[7] 7-zip claims to support SquashFS, although it is unsupported in the current 9.20 release; there is some support in alpha/beta versions.
See also[edit]
- Comparison of file systems
- List of file systems
- Cloop is a compressed loopback device module for the Linux kernel
- Cramfs is another read-only compressed file system
- e2compr provides compression for ext2
References[edit]
- ^ "Official Squashfs LZMA". Squashfs-lzma.org. Retrieved 2012-11-08.
- ^ "Linux 2 6 34 - Linux Kernel Newbies". Kernelnewbies.org. Retrieved 2012-11-08.
- ^ "Linux 2 6 38 - Linux Kernel Newbies". Kernelnewbies.org. Retrieved 2012-11-08.
- ^ "Linux 2 6 35 - Linux Kernel Newbies". Kernelnewbies.org. Retrieved 2012-11-08.
- ^ "The OpenWrt Flash Layout - OpenWrt Wiki". Wiki.openwrt.org. 2012-08-25. Retrieved 2012-11-08.
- ^ "Btrfs and Squashfs merged into Linux kernel - The H Open: News and Features". Heise-online.co.uk. 2009-01-10. Retrieved 2012-11-08.
- ^ "Squashfs tools for Windows; Forum Thread". Retrieved 2012-12-16.
External links[edit]
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