Squashfs 4.2 released (28th February 2011). Please see the CHANGES and README files in the new file release.

Squashfs is a compressed read-only filesystem for Linux. Squashfs is intended for general read-only filesystem use, for archival use (i.e. in cases where a .tar.gz file may be used), and in constrained block device/memory systems (e.g. embedded systems) where low overhead is needed.

You can go to the download page or the summary page. On the summary page there are links to the public forums, and the mailing lists. Queries, problems, etc. please send a message to the Squashfs mailing list, or use the trackers available on the Squashfs sourceforge page.

Squashfs presentation at CELF ELC-E 2008

Slides and a video of a presentation the author gave at the 2008 CELF Embedded Linux Europe conference are available.

Donations

Help sponsor Squashfs development!

Maintaining and improving Squashfs is a lot of work, but Squashfs is one of the only widely used Linux file systems that has no company backing. Squashfs development is funded soley by the author, partially supported by donations from companies and individuals that want to improve Squashfs for themselves and others.

Mainlining of Squashfs only became possible when CELF (Consumer Electronics Linux Forum) offered to contribute to the costs, which allowed the author to work full-time on the project.

There's lots of exciting new improvements to Squashfs in the pipeline, and if your company is a serious user of Squashfs, please consider accelerating development of Squashfs by donating.

Donatations can be made from the Squashfs sourceforge homepage, or if you prefer by contacting the author privately.

Releases

There are a number of different Squashfs releases available on the downloads page. The following gives brief details on them.

Squashfs 4.2

This is the latest release, for users of 2.6.29 and later kernels

Squashfs 4.1

Previous release without XZ compression support. For users of 2.6.29 and later kernels

Squashfs 3.4

This is the last 3.x release, for users of pre-2.6.29 kernels

Squashfs 3.0

First 3.x release, for users of pre-2.6.12 kernels, and 2.4.x kernels. This is the last release that supported 2.4 kernels

Squashfs 2.2-r2

This is the last 2.x release, for users of older kernels patched with Squashfs 2.

Squashfs 1.3r3

This is the last 1.x release, for users of older kernels patched with Squashfs 1.

Squashfs overview

• Data, inodes and directories are compressed.
• Squashfs stores full uid/gids (32 bits), and file creation time.
• Files up to 2^64 bytes are supported. Filesystems can be up to 2^64 bytes.
• Inode and directory data are highly compacted, and packed on byte boundaries. Each compressed inode is on average 8 bytes in length (the exact length varies on file type, i.e. regular file, directory, symbolic link, and block/char device inodes have different sizes).
• Squashfs can use block sizes up to 1Mbytes (the default size is 128K). Using 128K blocks achieves greater compression ratios than the normal 4K block size.
• File duplicates are detected and removed.
• Both big and little endian architectures are supported. The mksquashfs program can generate filesystems for different endian architectures for cases where the host byte ordering is different to the target. This is useful for embedded systems.

Installing squashfs

The squashfs file release contains a README, the squashfs patch files, and the squashfs-tools directory (mksquashfs). Please see the INSTALL file for install instructions.

Using squashfs

The README file contains details on using squashfs, and contains brief filesystem design notes...

Contact

The author can be contacted by email, phillip at lougher.demon.co.uk or plougher at users.sourceforge.net.