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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | ARGUMENTS | OPTIONS | EXIT STATUS | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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MKFS.CRAMFS(8) System Administration MKFS.CRAMFS(8)
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(8)) 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.)
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.
-v
Enable verbose messaging.
-E
Treat all warnings as errors, which are reflected as command
exit status.
-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 the specified endianness. The default is host.
-i file
Insert a file to cramfs file system.
-n name
Set name of the cramfs file system.
-p
Pad by 512 bytes for boot code.
-s
This option is ignored. Originally the -s turned on directory
entry sorting.
-z
Make explicit holes.
-l[=mode]
Use an exclusive BSD lock for the device or file that is
operated upon. The optional argument mode can be yes (1), no
(0), or nonblock. If the mode argument is omitted, it defaults
to yes. This option overrides the environment variable
$LOCK_BLOCK_DEVICE. The default is to not use any lock at all,
but using a lock is recommended to avoid collisions with
systemd-udevd(8) or other tools.
-h, --help
Display help text and exit.
-V, --version
Display version and exit.
0
success
8
operation error, such as unable to allocate memory
fsck.cramfs(8), mount(8)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
The mkfs.cramfs command is part of the util-linux package which
can be downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
part of the util-linux (a random collection of Linux utilities)
project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) If you discover any
rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
util-linux 2.42-start-521-ec46 2025-08-09 MKFS.CRAMFS(8)
Pages that refer to this page: fsck.cramfs(8), systemd-makefs@.service(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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