CramFS

The cramfs (Compressed ROM File System, alternatively, " cram a filesystem ontological a small ROM" ) is a free and GPL'ed Read-only file system with integrated data compression under Linux. It is mainly used in embedded systems, which is why a focus on the simplicity and efficiency of storage space required was laid.

Unlike a conventional compressed cramfs file system does not have to unpack, but it can be accessed directly. For this reason, use some Linux distributions the cramfs file system for initial ram disks (Debian ) or as an installation images (SuSE to openSUSE 10.2 ) because they are subject to some restrictions on their size. In embedded systems such as wireless routers cramfs is used.

Technology

Files in cramfs compressed with zlib. The metadata of these files are uncompressed, but are in a tighter structure represented as in conventional file systems. Since a write access to a compressed file system is not easy to implement, can be accessed for reading cramfs.

Processing

To create a cramfs file system and add files in it, tools like mkcramfs supplied as standard. For processing under Linux, the contents must be copied to a directory. Can then be created from the directory a new image. On Windows, there are tools for direct manipulation. One of these is newtuxflashtools.zip.

Technical Characteristics

Cramfs has some limitations such as:

• File sizes are limited to 16MB
• The maximum size of a file system is just over 256MB, the last file on the file system must begin before the end of the 256MB block, but may also be enough.

Alternatives

Squashfs is a compressed file system published in 2002, which compared to cramfs offers among other things a more effective compression and cope with larger files.