mtd-utils
=========
This package provides userspace utilities for working with Linux MTD and UBI
infrastructure, as well as related filesystems (JFFS2, UBIFS).
MTD stands for "Memory Technology Devices" and means flash, RAM and similar
chips, used for solid state storage on embedded devices. Think of e.g. a raw
nand-flash chip attached directly to an SoC via parallel or SPI bus, but
without _any_ special management like an eMMC has. The MTD subsystem exposes
those devices to userspace as character devices. It provides a unified
interface, but does not attempt to hide the page vs erase-block device
geometry or issues involved in dealing with the underlying storage, like wear
or bad blocks.
For this purpose, UBI provides a layer on top of MTD that hides away some
of those complexities. UBI also implements LVM-like logical volume partitioning
and some other useful capabilities.
UBI does not emulate block device like storage. UBI volumes are exposed as
character devices with page vs erase-block access geometry, much like MTD
partitions. But they behave more like a flash chip with "idealized" properties
and transparent wear-leveling.
JFFS2 is a flash friendly filesystem. It predates UBI and is designed to run
on top of raw MTD, implementing its own wear leveling.
The more recent UBIFS (formerly JFFS3) can be used on top of UBI volumes and
offers a number of improvements over JFFS2, offers newer compression schemes
and advanced features like file-level encryption and authentication.
Installing
----------
mtd-utils are packaged by a number of Linux distributions[0] and can be
installed via the package management system. A Yocto recipe is available
as well[1] as part of the openembedded-core layer.
Should the tools be too big for on-device use, the BusyBox project provides
compatible clone versions.
Before making this choice however, please note that some "heavy weight" tools
like mkfs.ubifs are typically not needed on the device itself. The kernel
module can format a volume on first mount. Other, heavy weight tools like lsmtd
can be disabled via a configure flag.
[0] https://repology.org/project/mtd-utils/versions
[1] https://layers.openembedded.org/layerindex/recipe/262/
How to get the source
---------------------
The official git repository and release tarballs are hosted on infradead.org:
Relase tarballs: ftp://ftp.infradead.org/pub/mtd-utils
git repository: git://git.infradead.org/mtd-utils.git
This is also where the website and documentation are hosted:
http://www.linux-mtd.infradead.org/
A http mirror is also provided on infraroot.at:
Relase tarballs: https://infraroot.at/pub/mtd
git repository: https://git.infraroot.at/mtd-utils.git
There are a number of mirrored repositories on GitHub, but this is not where
official development takes place. If you want to contribute upstream, please
do not open any issues or pull requests there. Upstream development is done
via mailing list (see below).
How to build
------------
mtd-utils uses an autotools based build system. If you are building the git
tree, you first need to run `./autogen.sh`. This sets up the build system
and requires autoconf, automake and possibly other autotools to be installed.
After unpacking a tarball (or running autogen.sh) simply run:
$ ./configure
$ make
to build the package. This does not require autotools to be installed, but
does need pkg-config, make, etc...
There are a number of configure switches to tune the build.
Run `./configure --help` to get an overview.
For compiling mtd-utils, you need development packages for the following
dependency libraries:
zlib (optional dependency for mkfs.ubifs, mkfs.jffs2)
lzo2 (optional dependency for mkfs.ubifs, mkfs.jffs2)
zstd (optional dependency for mkfs.ubifs)
libuuid* (required by mkfs.ubifs)
libselinux (optional dependency for mkfs.ubifs)
openssl (optional dependency for mkfs.ubifs)
* this library is part of util-linux, aka util-linux-ng and some distributions
package it under that name.
For xattr & acl support in mkfs.ubifs and mkfs.jffs2, the build system looks
for the "sys/xattr.h" and "sys/acl.h" header files. Depending on your
distributions, those may be packaged as part of libattr and libacl
respectively.
Please note that the mkfs tools are optional and can be disabled via a
configure flag. This should also remove any library dependencies.
How to contribute
-----------------
Development of mtd-utils takes place on the linux-mtd mailing list:
mailto: linux-mtd@lists.infradead.org
archive: https://lists.infradead.org/pipermail/linux-mtd/
You can subscribe here: http://lists.infradead.org/mailman/listinfo/linux-mtd/
or simply send "subscribe" to linux-mtd-request@lists.infradead.org
Contributions are submitted in the form of plain text patches,
using `git send-email` or similar.
Please prefix your subject with "mtd-utils: " to make them easier to spot.
It may take a few days for a patch to be picked up. This is in part done
intentionally to allow other people to comment on it. If it's been more
than a week and you feel your patch might have been overlooked, please send
a friendly ping, or re-submit the patch series with "[RESEND]" in the subject.
There is also a #mtd IRC channel on irc.oftc.net
