Section: System Administration (8)
Updated: April 2013Index
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mkfs.cramfs - make compressed ROM file system
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 16 MB.
Maximum file system size is a little under 272 MB. (The last file on the
file system must begin before the 256 MB block, but can extend past it.)
is simply the root of the directory tree that we want to generate a
compressed filesystem out of.
will contain the cram file system, which later can be mounted.
Enable verbose messaging.
Treat all warnings as errors, which are reflected as command return value.
- -b blocksize
Use defined block size, which has to be divisible by page size.
- -e edition
Use defined file system edition number in superblock.
- -N big, little, host
Use defined endianness. Value defaults to
- -i file
to cramfs file system.
- -n name
Set name of the cramfs file system.
Pad by 512 bytes for boot code.
This option is ignored. Originally the -s turned on directory entry
Make explicit holes. Use of this option will require 2.3.39 kernel, or newer.
Display version information and exit.
Display help and exit.
operation error, such as unable to allocate memory
The example command is part of the util-linux package and is available from
Linux Kernel Archive
- EXIT STATUS
- SEE ALSO