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![Phillip Lougher](/assets/img/avatar_default.png)
Squashfs now supports XZ and LZO compression in addition to ZLIB. As such it no longer makes sense to always include ZLIB support. In particular embedded systems may only use LZO or XZ compression, and the ability to exclude ZLIB support will reduce kernel size. Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
101 lines
3.6 KiB
Text
101 lines
3.6 KiB
Text
config SQUASHFS
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tristate "SquashFS 4.0 - Squashed file system support"
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depends on BLOCK
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help
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Saying Y here includes support for SquashFS 4.0 (a Compressed
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Read-Only File System). Squashfs is a highly compressed read-only
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filesystem for Linux. It uses zlib, lzo or xz compression to
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compress both files, inodes and directories. Inodes in the system
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are very small and all blocks are packed to minimise data overhead.
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Block sizes greater than 4K are supported up to a maximum of 1 Mbytes
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(default block size 128K). SquashFS 4.0 supports 64 bit filesystems
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and files (larger than 4GB), full uid/gid information, hard links and
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timestamps.
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Squashfs is intended for general read-only filesystem use, for
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archival use (i.e. in cases where a .tar.gz file may be used), and in
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embedded systems where low overhead is needed. Further information
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and tools are available from http://squashfs.sourceforge.net.
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If you want to compile this as a module ( = code which can be
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inserted in and removed from the running kernel whenever you want),
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say M here and read <file:Documentation/modules.txt>. The module
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will be called squashfs. Note that the root file system (the one
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containing the directory /) cannot be compiled as a module.
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If unsure, say N.
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config SQUASHFS_XATTR
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bool "Squashfs XATTR support"
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depends on SQUASHFS
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help
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Saying Y here includes support for extended attributes (xattrs).
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Xattrs are name:value pairs associated with inodes by
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the kernel or by users (see the attr(5) manual page).
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If unsure, say N.
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config SQUASHFS_ZLIB
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bool "Include support for ZLIB compressed file systems"
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depends on SQUASHFS
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select ZLIB_INFLATE
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default y
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help
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ZLIB compression is the standard compression used by Squashfs
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file systems. It offers a good trade-off between compression
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achieved and the amount of CPU time and memory necessary to
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compress and decompress.
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If unsure, say Y.
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config SQUASHFS_LZO
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bool "Include support for LZO compressed file systems"
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depends on SQUASHFS
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select LZO_DECOMPRESS
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help
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Saying Y here includes support for reading Squashfs file systems
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compressed with LZO compression. LZO compression is mainly
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aimed at embedded systems with slower CPUs where the overheads
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of zlib are too high.
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LZO is not the standard compression used in Squashfs and so most
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file systems will be readable without selecting this option.
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If unsure, say N.
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config SQUASHFS_XZ
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bool "Include support for XZ compressed file systems"
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depends on SQUASHFS
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select XZ_DEC
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help
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Saying Y here includes support for reading Squashfs file systems
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compressed with XZ compression. XZ gives better compression than
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the default zlib compression, at the expense of greater CPU and
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memory overhead.
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XZ is not the standard compression used in Squashfs and so most
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file systems will be readable without selecting this option.
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If unsure, say N.
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config SQUASHFS_EMBEDDED
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bool "Additional option for memory-constrained systems"
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depends on SQUASHFS
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help
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Saying Y here allows you to specify cache size.
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If unsure, say N.
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config SQUASHFS_FRAGMENT_CACHE_SIZE
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int "Number of fragments cached" if SQUASHFS_EMBEDDED
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depends on SQUASHFS
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default "3"
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help
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By default SquashFS caches the last 3 fragments read from
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the filesystem. Increasing this amount may mean SquashFS
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has to re-read fragments less often from disk, at the expense
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of extra system memory. Decreasing this amount will mean
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SquashFS uses less memory at the expense of extra reads from disk.
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Note there must be at least one cached fragment. Anything
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much more than three will probably not make much difference.
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