Cramfs 844158 201566870 2008-03-28T13:11:10Z 82.119.242.94 cramfs on sourceforge is obsolete, linked to util-linux instead The '''compressed ROM file system''' (or '''cramfs''') is a [[Free software|free]] ([[GNU General Public License|GPL]]'ed) read-only [[Linux kernel|Linux]] [[file system]] designed for simplicity and space-efficiency. It is mainly used in [[embedded system]]s and small-footprint systems. Unlike a compressed image of a conventional file system, a cramfs image can be used as it is i.e. without the need to decompress the image first. For this reason, some [[Linux distribution]]s also use cramfs for [[initrd]] images ([[Debian]] 3.1 in particular) and installation images ([[SUSE Linux]] in particular), where there are constraints on memory and image size. == Design == Files on cramfs file systems are [[zlib]]-compressed one page at a time to allow random read access. The meta-data is not compressed, but is expressed in a terse representation that is designed to be more space-efficient than conventional file systems. The file system is intentionally read-only to simplify its design; random write access for compressed files is difficult to implement. cramfs ships with a utility (<code>mkcramfs</code>) to pack files into new cramfs images. File sizes are limited to less than 16MB. Maximum file system size is a little over 256MB. (The last file on the file system must begin before the 256MB block, but can extend past it.) == See also == {{portal|Free software|Free Software Portal Logo.svg}} * [[List of file systems]] * [[Comparison of file systems]] * [[SquashFS]], a read-only compressed file system * [[Util-linux]] contains the cramfs utilities [[Category:Free special purpose file systems]] [[Category:Compression file systems]] [[Category:Linux file systems]] [[de:CramFS]] [[fr:Cramfs]] [[ru:Cramfs]]