SquashFS
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Squashfs (.sfs) is a free (GPL) compressed read-only file system for the Linux kernel. Squashfs compresses files, inodes and directories, and supports block sizes up to 1024 KB for greater compression.
Squashfs is intended for general read-only file system use, for archival use (i.e. in cases where a tar file may be used), and in constrained block device/memory systems (e.g. embedded systems) where low overhead is needed. The standard version of Squashfs uses gzip compression.
[edit] Uses
SquashFS is used by the Live CD versions of Finnix, Ubuntu, DD-WRT and probably many more Linux distributions. The Helix forensics Live CD also makes use of SquashFS. It is also combined with an 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 with the ability to drastically alter the distribution while running it off of a cd. One distribution that uses this combo is Slax and its derivatives such as the Backtrack Live CD as well as Debian Live.
Note that as the on-disk format of SquashFS have not stabilized yet[1], it is not ready for long-term archival use (i.e. in cases where a tar file may be used).
[edit] See also
- List of file systems
- Comparison of file systems
- Cramfs is another read-only compressed file system
- zisofs is a transparent compression extension to the ISO 9660 file system
- Cloop is a compressed loopback device module for the Linux kernel
- e2compr is an extension to the ext2 file system driver in the Linux kernel to support online compression
- http://www.squashfs-lzma.org/ has the patches for LZMA to achieve higher compression Vs Zlib
