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mdadm is a utility used to create and manage software RAID devices implemented through Multiple devices driver (MD) in kernel. It supports following RAID metadata formats:

  • Linux native RAID:

    Known as native or native RAID. First and default metadata format. Metadata management is implemented in MD driver.

  • Matrix Storage Manager Support (no reference, metadata format documentation is proprietary).

    Known as IMSM. Metadata format developed and maintained by Intel® as a part of VROC solution. There are some functional differences between native and imsm. The most important difference is that the metadata is managed from userspace.

    CAUTION: imsm is compatible with Intel RST, however it is not officially supported. You are using it on your own risk.

  • Common RAID DDF Specification Revision

    IMPORTANT: DDF is in maintenance only mode. There is no active development around it. Please do not use it in new solutions.

Questions and Support

This Github site is not right place to ask if your are looking for:

  • support from Linux Raid Community;
  • support with kernel issues;

This is the place where development of mdadm application is done. Please, do not use for looking for support. You should always ask on Mailing List.

Please use issues if you have confirmation that issue you are experiencing is related to mdadm components:

  • mdadm;
  • mdmon;
  • raid6check;
  • swap_super;
  • test_stripe;
  • systemd services ( see systemd/);
  • udev rules;
  • manual pages (including md.man)

For example:

  • mdadm issues (e.g segfaults, memory leaks, crashes, bad communication with MD driver);
  • feature requests for mdadm;
  • suggestions or minor fixes requested (e.g. better error messages);

Generally, if you are not sure it is better to ask on Mailing List first.

How to Contribute

Effective immediately Github is the primary location for mdadm. Use pull request to contribute.

It was originally hosted on kernel.org. You can access the old repository here.

Patches sent through Mailing list are accepted but Github is preferred. Sent then to ML only if you cannot use Github. Please add "mdadm:" to the subject to allow automation to create Github Pull Request and run checks.

NOTE: Maintainers may ask you to send RFC to mailing list if the proposed code requires consultation with kernel developers.

Kernel coding style is used. Please familiarize with general kernel submitting patches documentation. Formatting, tags and commit message guidelines applies to mdadm.

Checkpatch script is run on every patch in pull request so be sure that your commits are not generating issues. There are some excludes, so the best is to follow github checkpatch action result.

Pull Request are closed by Rebase and Merge option, so it requires to keep every commit meaningful. Kernel style requires that. The review changes must be pushed with push --force to the chosen branch, then Pull Request will be automatically updated.

Maintainers of mdadm repository on kernel.org

If there are differences between github and kernel.org, please contact kernel.org mdadm maintainers:

Minimal supported kernel version

We do not support kernel versions below v3.10. Please be aware that maintainers may remove workarounds and fixes for legacy issues.

Dependencies

The following packages are required for compilation:

RHEL SLES Debian/Ubuntu
pkgconf pkg-config pkg-config
gcc gcc gcc
make make make
libudev-devel libudev-devel libudev-dev

Compiling mdadm

Run make command to compile mdadm.

Specifying more jobs e.g. make -j4 can decrease compilation time significantly.

Various values can be specified for the CXFLAGS variable to customize the build process:

  • Run make CXFLAGS=-ggdb to include gdb debugging information.
  • Run make CXFLAGS=-DDEBUG to enable additional debug information through dprintf statements and call traces.
  • Run make CXFLAGS=-DNO_LIBUDEV to compile without libudev.

To build with more than one option specified in CXFLAGS, separate each option with a space, e.g. make CXFLAGS="-ggdb -DDEBUG".

Additionally, the EXTRAVERSION variable can be set to build with user-friendly version label, useful when customizing mdadm builds or labeling some instance in between major releases, e.g. make EXTRAVERSION="custom-label".

Installing mdadm

Before installing mdadm, it is advised to uninstall vendor-provided packages (mdadm.deb, mdadm.rpm etc.) in order to avoid configuration issues.

Run make install command to install mdadm. This command invokes the following targets:

  • install-bin
  • install-man
  • install-udev

After installing mdadm, consider rebuilding initramfs to ensure the changes take effect.

List of installation targets:

  • Run make install-bin to install the mdadm and mdmon binary files.
  • Run make install-systemd to install the systemd services.
  • Run make install-udev to install the udev rules.
  • Run make install-man to install the manual pages (mdadm.8, md.4, mdadm.conf.5, mdmon.8).

The following targets are deprecated and should not be used:

  • install-static
  • install-tcc
  • install-uclibc
  • install-klibc

License

It is released under the terms of the GNU General Public License version 2 as published by the Free Software Foundation.