squashfs-tools/RELEASE-READMEs/README-4.1 - nest-cam/4320010/squashfs-tools - Git at Google

 	SQUASHFS 4.1 - A squashed read-only filesystem for Linux

 	Copyright 2002-2010 Phillip Lougher <phillip@lougher.demon.co.uk>

 	Released under the GPL licence (version 2 or later).

 Welcome to Squashfs 4.1.  This is a tools only release, support for Squashfs
 file systems is in mainline (2.6.29 and later).

 New features in Squashfs-tools 4.1
 ----------------------------------

   1. Support for extended attributes
   2. Support for LZMA and LZO compression
   3. New pseudo file features

 Compatiblity
 ------------

 Mksquashfs 4.1 generates 4.0 filesystems.  These filesystems are fully
 compatible/interchangable with filesystems generated by Mksquashfs 4.0 and are
 mountable on 2.6.29 and later kernels.

 Extended attributes (xattrs)
 ----------------------------

 Squashfs file systems now have extended attribute support.  The
 extended attribute implementation has the following features:

 1. Layout can store up to 2^48 bytes of compressed xattr data.
 2. Number of xattrs per inode unlimited.
 3. Total size of xattr data per inode 2^48 bytes of compressed data.
 4. Up to 4 Gbytes of data per xattr value.
 5. Inline and out-of-line xattr values supported for higher performance
    in xattr scanning (listxattr & getxattr), and to allow xattr value
    de-duplication.
 6. Both whole inode xattr duplicate detection and individual xattr value
    duplicate detection supported.  These can obviously nest, file C's
    xattrs can be a complete duplicate of file B, and file B's xattrs
    can be a partial duplicate of file A.
 7. Xattr name prefix types stored, allowing the redundant "user.", "trusted."
    etc. characters to be eliminated and more concisely stored.
 8. Support for files, directories, symbolic links, device nodes, fifos
    and sockets.

 Extended attribute support is in 2.6.35 and later kernels.  File systems
 with extended attributes can be mounted on 2.6.29 and later kernels, the
 extended attributes will be ignored with a warning.

 LZMA and LZO compression
 ------------------------

 Squashfs now supports LZMA and LZO compression.

 LZO support is in 2.6.36 and newer kernels.  LZMA is not yet in mainline.

 New Mksquashfs options
 ----------------------

 -comp <comp>

     Select <comp> compression.

     The compression algorithms supported by the build of Mksquashfs can be
     found by typing mksquashfs without any arguments.  The compressors available
     are displayed at the end of the help message, e.g.

     Compressors available:
 	gzip (default)
 	lzma
 	lzo

     The default compression used when -comp isn't specified on the command line
     is indicated by "(default)".

 -no-xattrs
     Don't store extended attributes

 -xattrs
     Store extended attributes

     The default behaviour of Mksquashfs with respect to extended attribute
     storage is build time selectable.  The Mksquashfs help message indicates
     whether extended attributes are stored or not, e.g.

 	-no-xattrs		don't store extended attributes
 	-xattrs			store extended attributes (default)

     shows that extended attributes are stored by default, and can be disabled
     by the -no-xattrs option.

 	-no-xattrs		don't store extended attributes (default)
 	-xattrs			store extended attributes

     shows that extended attributes are not stored by default, storage can be
     enabled by the -xattrs option.


 -noX
 -noXattrCompression
     Don't compress extended attributes


 New Unsquashfs options
 ----------------------

 -n[o-xattrs]
     Don't extract xattrs in filesystem

 -x[attrs]
     Extract xattrs in filesystem

     The default behaviour of Unsquashfs with respect to extended attributes
     is build time selectable.  The Unsquashfs help message indicates whether
     extended attributes are stored or not, e.g.

 	-no[-xattrs]		don't extract xattrs in file system
 	-x[attrs]		extract xattrs in file system (default)

     shows that xattrs are extracted by default.

 	-no[-xattrs]		don't extract xattrs in file system (default)
 	-x[attrs]		extract xattrs in file system

     shows that xattrs are not extracted by default.


 New pseudo file support
 -----------------------

 Mksquashfs supports pseudo files, these allow fake files, directories, character
 and block devices to be specified and added to the Squashfs filesystem being
 built, rather than requiring them to be present in the source directories.
 This, for example, allows device nodes to be added to the filesystem without
 requiring root access.

 Mksquashfs 4.1 adds support for "dynamic pseudo files" and a modify operation.
 Dynamic pseudo files allow files to be dynamically created when Mksquashfs
 is run, their contents being the result of running a command or piece of
 shell script.  The modifiy operation allows the mode/uid/gid of an existing
 file in the source filesystem to be modified.

 Two Mksquashfs options are supported, -p allows one pseudo file to be specified
 on the command line, and -pf allows a pseudo file to be specified containing a
 list of pseduo definitions, one per line.

 Pseudo operations
 -----------------

 1. Creating a dynamic file
 --------------------------

 Pseudo definition

 Filename f mode uid gid command

 mode is the octal mode specifier, similar to that expected by chmod.

 uid and gid can be either specified as a decimal number, or by name.

 command can be an executable or a piece of shell script, and it is executed
 by running "/bin/sh -c command".   The stdout becomes the contents of
 "Filename".

 Examples:

 Running a basic command
 -----------------------

 /somedir/dmesg f 444 root root dmesg

 creates a file "/somedir/dmesg" containing the output from dmesg.

 Executing shell script
 ----------------------

 RELEASE f 444 root root \
 		if [ ! -e /tmp/ver ]; then \
 			echo 0 > /tmp/ver; \
 		fi; \
                 ver=`cat /tmp/ver`; \
                 ver=$((ver +1)); \
                 echo $ver > /tmp/ver; \
                 echo -n `cat /tmp/release`; \
                 echo "-dev #"$ver `date` "Build host" `hostname`

 Creates a file RELEASE containing the release name, date, build host, and
 an incrementing version number.  The incrementing version is a side-effect
 of executing the shell script, and ensures every time Mksquashfs is run a
 new version number is used without requiring any other shell scripting.

 The above example also shows that commands can be split across multiple lines
 using "\".  Obviously as the script will be presented to the shell as a single
 line, a semicolon is need to separate individual shell commands within the
 shell script.

 Reading from a device (or fifo/named socket)
 --------------------------------------------

 input f 444 root root dd if=/dev/sda1 bs=1024 count=10

 Copies 10K from the device /dev/sda1 into the file input.  Ordinarily Mksquashfs
 given a device, fifo, or named socket will place that special file within the
 Squashfs filesystem, the above allows input from these special files to be
 captured and placed in the Squashfs filesystem.

 2. Creating a block or character device
 ---------------------------------------

 Pseudo definition

 Filename type mode uid gid major minor

 Where type is either
 	b - for block devices, and
 	c - for character devices

 mode is the octal mode specifier, similar to that expected by chmod.

 uid and gid can be either specified as a decimal number, or by name.

 For example:

 /dev/chr_dev c 666 root root 100 1
 /dev/blk_dev b 666 0 0 200 200

 creates a character device "/dev/chr_dev" with major:minor 100:1 and
 a block device "/dev/blk_dev" with major:minor 200:200, both with root
 uid/gid and a mode of rw-rw-rw.

 3. Creating a directory
 -----------------------

 Pseudo definition

 Filename d mode uid gid

 mode is the octal mode specifier, similar to that expected by chmod.

 uid and gid can be either specified as a decimal number, or by name.

 For example:

 /pseudo_dir d 666 root root

 creates a directory "/pseudo_dir" with root uid/gid and mode of rw-rw-rw.

 4. Modifying attributes of an existing file
 -------------------------------------------

 Pseudo definition

 Filename m mode uid gid

 mode is the octal mode specifier, similar to that expected by chmod.

 uid and gid can be either specified as a decimal number, or by name.

 For example:

 dmesg m 666 root root

 Changes the attributes of the file "dmesg" in the filesystem to have
 root uid/gid and a mode of rw-rw-rw, overriding the attributes obtained
 from the source filesystem.
	SQUASHFS 4.1 - A squashed read-only filesystem for Linux

	Copyright 2002-2010 Phillip Lougher <phillip@lougher.demon.co.uk>

	Released under the GPL licence (version 2 or later).

	Welcome to Squashfs 4.1. This is a tools only release, support for Squashfs
	file systems is in mainline (2.6.29 and later).

	New features in Squashfs-tools 4.1
	----------------------------------

	1. Support for extended attributes
	2. Support for LZMA and LZO compression
	3. New pseudo file features

	Compatiblity
	------------

	Mksquashfs 4.1 generates 4.0 filesystems. These filesystems are fully
	compatible/interchangable with filesystems generated by Mksquashfs 4.0 and are
	mountable on 2.6.29 and later kernels.

	Extended attributes (xattrs)
	----------------------------

	Squashfs file systems now have extended attribute support. The
	extended attribute implementation has the following features:

	1. Layout can store up to 2^48 bytes of compressed xattr data.
	2. Number of xattrs per inode unlimited.
	3. Total size of xattr data per inode 2^48 bytes of compressed data.
	4. Up to 4 Gbytes of data per xattr value.
	5. Inline and out-of-line xattr values supported for higher performance
	in xattr scanning (listxattr & getxattr), and to allow xattr value
	de-duplication.
	6. Both whole inode xattr duplicate detection and individual xattr value
	duplicate detection supported. These can obviously nest, file C's
	xattrs can be a complete duplicate of file B, and file B's xattrs
	can be a partial duplicate of file A.
	7. Xattr name prefix types stored, allowing the redundant "user.", "trusted."
	etc. characters to be eliminated and more concisely stored.
	8. Support for files, directories, symbolic links, device nodes, fifos
	and sockets.

	Extended attribute support is in 2.6.35 and later kernels. File systems
	with extended attributes can be mounted on 2.6.29 and later kernels, the
	extended attributes will be ignored with a warning.

	LZMA and LZO compression
	------------------------

	Squashfs now supports LZMA and LZO compression.

	LZO support is in 2.6.36 and newer kernels. LZMA is not yet in mainline.

	New Mksquashfs options
	----------------------

	-comp <comp>

	Select <comp> compression.

	The compression algorithms supported by the build of Mksquashfs can be
	found by typing mksquashfs without any arguments. The compressors available
	are displayed at the end of the help message, e.g.

	Compressors available:
	gzip (default)
	lzma
	lzo

	The default compression used when -comp isn't specified on the command line
	is indicated by "(default)".

	-no-xattrs
	Don't store extended attributes

	-xattrs
	Store extended attributes

	The default behaviour of Mksquashfs with respect to extended attribute
	storage is build time selectable. The Mksquashfs help message indicates
	whether extended attributes are stored or not, e.g.

	-no-xattrs don't store extended attributes
	-xattrs store extended attributes (default)

	shows that extended attributes are stored by default, and can be disabled
	by the -no-xattrs option.

	-no-xattrs don't store extended attributes (default)
	-xattrs store extended attributes

	shows that extended attributes are not stored by default, storage can be
	enabled by the -xattrs option.


	-noX
	-noXattrCompression
	Don't compress extended attributes


	New Unsquashfs options
	----------------------

	-n[o-xattrs]
	Don't extract xattrs in filesystem

	-x[attrs]
	Extract xattrs in filesystem

	The default behaviour of Unsquashfs with respect to extended attributes
	is build time selectable. The Unsquashfs help message indicates whether
	extended attributes are stored or not, e.g.

	-no[-xattrs] don't extract xattrs in file system
	-x[attrs] extract xattrs in file system (default)

	shows that xattrs are extracted by default.

	-no[-xattrs] don't extract xattrs in file system (default)
	-x[attrs] extract xattrs in file system

	shows that xattrs are not extracted by default.


	New pseudo file support
	-----------------------

	Mksquashfs supports pseudo files, these allow fake files, directories, character
	and block devices to be specified and added to the Squashfs filesystem being
	built, rather than requiring them to be present in the source directories.
	This, for example, allows device nodes to be added to the filesystem without
	requiring root access.

	Mksquashfs 4.1 adds support for "dynamic pseudo files" and a modify operation.
	Dynamic pseudo files allow files to be dynamically created when Mksquashfs
	is run, their contents being the result of running a command or piece of
	shell script. The modifiy operation allows the mode/uid/gid of an existing
	file in the source filesystem to be modified.

	Two Mksquashfs options are supported, -p allows one pseudo file to be specified
	on the command line, and -pf allows a pseudo file to be specified containing a
	list of pseduo definitions, one per line.

	Pseudo operations
	-----------------

	1. Creating a dynamic file
	--------------------------

	Pseudo definition

	Filename f mode uid gid command

	mode is the octal mode specifier, similar to that expected by chmod.

	uid and gid can be either specified as a decimal number, or by name.

	command can be an executable or a piece of shell script, and it is executed
	by running "/bin/sh -c command". The stdout becomes the contents of
	"Filename".

	Examples:

	Running a basic command
	-----------------------

	/somedir/dmesg f 444 root root dmesg

	creates a file "/somedir/dmesg" containing the output from dmesg.

	Executing shell script
	----------------------

	RELEASE f 444 root root \
	if [ ! -e /tmp/ver ]; then \
	echo 0 > /tmp/ver; \
	fi; \
	ver=`cat /tmp/ver`; \
	ver=$((ver +1)); \
	echo $ver > /tmp/ver; \
	echo -n `cat /tmp/release`; \
	echo "-dev #"$ver `date` "Build host" `hostname`

	Creates a file RELEASE containing the release name, date, build host, and
	an incrementing version number. The incrementing version is a side-effect
	of executing the shell script, and ensures every time Mksquashfs is run a
	new version number is used without requiring any other shell scripting.

	The above example also shows that commands can be split across multiple lines
	using "\". Obviously as the script will be presented to the shell as a single
	line, a semicolon is need to separate individual shell commands within the
	shell script.

	Reading from a device (or fifo/named socket)
	--------------------------------------------

	input f 444 root root dd if=/dev/sda1 bs=1024 count=10

	Copies 10K from the device /dev/sda1 into the file input. Ordinarily Mksquashfs
	given a device, fifo, or named socket will place that special file within the
	Squashfs filesystem, the above allows input from these special files to be
	captured and placed in the Squashfs filesystem.

	2. Creating a block or character device
	---------------------------------------

	Pseudo definition

	Filename type mode uid gid major minor

	Where type is either
	b - for block devices, and
	c - for character devices

	mode is the octal mode specifier, similar to that expected by chmod.

	uid and gid can be either specified as a decimal number, or by name.

	For example:

	/dev/chr_dev c 666 root root 100 1
	/dev/blk_dev b 666 0 0 200 200

	creates a character device "/dev/chr_dev" with major:minor 100:1 and
	a block device "/dev/blk_dev" with major:minor 200:200, both with root
	uid/gid and a mode of rw-rw-rw.

	3. Creating a directory
	-----------------------

	Pseudo definition

	Filename d mode uid gid

	mode is the octal mode specifier, similar to that expected by chmod.

	uid and gid can be either specified as a decimal number, or by name.

	For example:

	/pseudo_dir d 666 root root

	creates a directory "/pseudo_dir" with root uid/gid and mode of rw-rw-rw.

	4. Modifying attributes of an existing file
	-------------------------------------------

	Pseudo definition

	Filename m mode uid gid

	mode is the octal mode specifier, similar to that expected by chmod.

	uid and gid can be either specified as a decimal number, or by name.

	For example:

	dmesg m 666 root root

	Changes the attributes of the file "dmesg" in the filesystem to have
	root uid/gid and a mode of rw-rw-rw, overriding the attributes obtained
	from the source filesystem.