Saying Y here includes support for CramFs (Compressed ROM File
System). CramFs is designed to be a simple, small, and compressed
file system for ROM based embedded systems. CramFs is read-only,
limited to 256MB file systems (with 16MB files), and doesn't support
16/32 bits uid/gid, hard links and timestamps.

See <file:Documentation/filesystems/cramfs.txt> and
<file:fs/cramfs/README> for further information.

To compile this as a module, choose M here: the module will be called
cramfs. Note that the root file system (the one containing the
directory /) cannot be compiled as a module.

This filesystem is limited in capabilities and performance on
purpose to remain small and low on RAM usage. It is most suitable
for small embedded systems. If you have ample RAM to spare, you may
consider a more capable compressed filesystem such as SquashFS
which is much better in terms of performance and features.

If unsure, say N.

source code:

fs/cramfs/