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mkfs.cramfs — make compressed ROM file system
mkfs.cramfs [options]
directory file
Files on cramfs file systems are zlib-compressed one page at a time to allow random read access. The metadata is not compressed, but is expressed in a terse representation that is more space-efficient than conventional file systems.
The file system is intentionally read-only to simplify its design; random write access for compressed files is difficult to implement. cramfs ships with a utility (mkcramfs) to pack files into new cramfs images.
File sizes are limited to less than 16MB.
Maximum file system size is a little under 272MB. (The last file on the file system must begin before the 256MB block, but can extend past it.)
The directory is
simply the root of the directory tree that we want to
generate a compressed filesystem out of.
The file will
contain the cram file system, which later can be mounted.
−vEnable verbose messaging.
−ETreat all warnings as errors, which are reflected as command return value.
−b blocksizeUse defined block size, which has to be divisible by page size.
−e editionUse defined file system edition number in superblock.
−N big,
little, hostUse defined endianness. Value defaults to host.
−i fileInsert a file to cramfs file
system.
−n nameSet name of the cramfs file system.
−pPad by 512 bytes for boot code.
−sThis option is ignored. Originally the −s turned on directory entry sorting.
−zMake explicit holes. Use of this option will require 2.3.39 kernel, or newer.
−VDisplay version information and exit.
−hDisplay help and exit.
The example command is part of the util-linux package and is available from Linux Kernel Archive
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