INSTALL - platform/external/squashfs-tools - Git at Google

 			INSTALLING SQUASHFS

 The squashfs2.2-r2.tar.gz file contains this file, a README file,
 an ACKNOWLEDGEMENTS file, a CHANGES file, the squashfs patch
 directories/files, and the squashfs-tools directory (mksquashfs).

 1. Patching the kernel
 ----------------------

 There are twelve kernel patch directories depending on your linux kernel
 version.  If your kernel version isn't listed then try the patch for the nearest
 kernel listed.

 To patch your kernel, cd into the top level directory, and run the "patch"
 comand, e.g. assuming linux-2.4.20

 %cd /usr/src/linux-2.4.20
 %patch -p1 < location-of-squashfs/linux-2.4.20/squashfs2.2-patch

 Where "location-of-squashfs" is the path to the squashfs2.2 source directory.

 The squashfs patches patch the relevant kernel files to add configure support,
 initrd support, include files, and the squashfs directory under linux/fs/.
 Once patched, the kernel must be reconfigured, with squashfs support turned on
 (either Y/M) to ensure that inflate support is built into the kernel.  The
 squashfs kernel option can be found in the filesystems submenu of the
 configure menus.  In the 2.6.x kernels, the squashfs option is hiding in
 the new miscellaneous filesystems submenu near the bottom of the filesystems
 submenu.

 In SquashFS 2.2 there are a new set of options which are intended for use by
 embedded systems with low memory.  At the "Additional options for
 memory-constrained systems" prompt, please say NO unless you know what you're
 doing!  Saying Y here allows you to specify cache sizes and how Squashfs
 allocates memory.

 The "Number of fragments cached" prompt allows the number of fragments cached
 to be controlled.  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.

 The "Use Vmalloc rather than Kmalloc" prompt allows you to tell SquashFS to
 use Vmalloc.  By default SquashFS uses kmalloc to obtain fragment cache memory.
 Kmalloc memory is the standard kernel allocator, but it can fail on memory
 constrained systems.  Because of the way Vmalloc works, Vmalloc can succeed
 when kmalloc fails.  Specifying this option will make SquashFS always use
 Vmalloc to allocate the fragment cache memory.

 2. Building squashfs tools
 --------------------------

 The squashfs-tools directory contains the mksquashfs program.  This can be
 made by typing make.  The source files use a local copy of squashfs_fs.h
 (included in the kernel patches) allowing the tools to be made without needing
 to patch the kernel.  The program uses Large File Support
 (64 bit offsets etc.) and so a relatively recent glibc is needed.
	INSTALLING SQUASHFS

	The squashfs2.2-r2.tar.gz file contains this file, a README file,
	an ACKNOWLEDGEMENTS file, a CHANGES file, the squashfs patch
	directories/files, and the squashfs-tools directory (mksquashfs).

	1. Patching the kernel
	----------------------

	There are twelve kernel patch directories depending on your linux kernel
	version. If your kernel version isn't listed then try the patch for the nearest
	kernel listed.

	To patch your kernel, cd into the top level directory, and run the "patch"
	comand, e.g. assuming linux-2.4.20

	%cd /usr/src/linux-2.4.20
	%patch -p1 < location-of-squashfs/linux-2.4.20/squashfs2.2-patch

	Where "location-of-squashfs" is the path to the squashfs2.2 source directory.

	The squashfs patches patch the relevant kernel files to add configure support,
	initrd support, include files, and the squashfs directory under linux/fs/.
	Once patched, the kernel must be reconfigured, with squashfs support turned on
	(either Y/M) to ensure that inflate support is built into the kernel. The
	squashfs kernel option can be found in the filesystems submenu of the
	configure menus. In the 2.6.x kernels, the squashfs option is hiding in
	the new miscellaneous filesystems submenu near the bottom of the filesystems
	submenu.

	In SquashFS 2.2 there are a new set of options which are intended for use by
	embedded systems with low memory. At the "Additional options for
	memory-constrained systems" prompt, please say NO unless you know what you're
	doing! Saying Y here allows you to specify cache sizes and how Squashfs
	allocates memory.

	The "Number of fragments cached" prompt allows the number of fragments cached
	to be controlled. 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.

	The "Use Vmalloc rather than Kmalloc" prompt allows you to tell SquashFS to
	use Vmalloc. By default SquashFS uses kmalloc to obtain fragment cache memory.
	Kmalloc memory is the standard kernel allocator, but it can fail on memory
	constrained systems. Because of the way Vmalloc works, Vmalloc can succeed
	when kmalloc fails. Specifying this option will make SquashFS always use
	Vmalloc to allocate the fragment cache memory.

	2. Building squashfs tools
	--------------------------

	The squashfs-tools directory contains the mksquashfs program. This can be
	made by typing make. The source files use a local copy of squashfs_fs.h
	(included in the kernel patches) allowing the tools to be made without needing
	to patch the kernel. The program uses Large File Support
	(64 bit offsets etc.) and so a relatively recent glibc is needed.