Saying Y here includes support for SquashFS 4.0 (a Compressed Read-Only File System). Squashfs is a highly compressed read-only filesystem for Linux. It uses zlib, lzo or xz compression to compress both files, inodes and directories. Inodes in the system are very small and all blocks are packed to minimise data overhead. Block sizes greater than 4K are supported up to a maximum of 1 Mbytes (default block size 128K). SquashFS 4.0 supports 64 bit filesystems and files (larger than 4GB), full uid/gid information, hard links and timestamps. Squashfs is intended for general read-only filesystem use, for archival use (i.e. in cases where a .tar.gz file may be used), and in embedded systems where low overhead is needed. Further information and tools are available from http://squashfs.sourceforge.net. If you want to compile this as a module ( = code which can be inserted in and removed from the running kernel whenever you want), say M here and read <file:Documentation/modules.txt>. The module will be called squashfs. Note that the root file system (the one containing the directory /) cannot be compiled as a module. If unsure, say N.
Saying Y here includes support for extended attributes (xattrs). Xattrs are name:value pairs associated with inodes by the kernel or by users (see the attr(5) manual page). If unsure, say N.
Saying Y here includes support for reading Squashfs file systems compressed with LZO compression. LZO compression is mainly aimed at embedded systems with slower CPUs where the overheads of zlib are too high. LZO is not the standard compression used in Squashfs and so most file systems will be readable without selecting this option. If unsure, say N.
Saying Y here includes support for reading Squashfs file systems compressed with XZ compression. XZ gives better compression than the default zlib compression, at the expense of greater CPU and memory overhead. XZ is not the standard compression used in Squashfs and so most file systems will be readable without selecting this option. If unsure, say N.
Saying Y here allows you to specify cache size. If unsure, say N.
By default SquashFS caches the last 3 fragments read from the filesystem. Increasing this amount may mean SquashFS has to re-read fragments less often from disk, at the expense of extra system memory. Decreasing this amount will mean SquashFS uses less memory at the expense of extra reads from disk. Note there must be at least one cached fragment. Anything much more than three will probably not make much difference.