Cramfs

Compressed ROM file system ( cramfs ) is a free Linux compressed file system for ROM - based embedded systems . Cramfs provides support for working with FS directly reflected in memory (for example, in NVRAM). In combination with the use of uncompressed areas of memory, this feature allows you to organize "execution in place" (execute-in-place) without additional copying to RAM. Cramfs is read-only (although there are patches that add support for temporary data modification ^[1] ), it is limited to 256 * 10 ^ 6 bytes for the file system (and 16 * 10 ^ 6 bytes per file), and also does not support 16/32 -bit user and group identifiers .

You can create an image of the cramfs file system using the mkcramfs utility.

Theoretically, the size of the last file may exceed the 256MB boundary. Hard links are supported, but the link count is always equal to one, including for directories. Directories have no "." And ".." elements. Timestamps for files are not stored, all files have a creation date of January 1, 1970, but recently modified files may have a different date, but this lasts until the file system node is cached in memory, i.e. the timestamp is reset back to 1970 when the file system was remounted or zeroing the cache .