dracut (software)

Dracut
Original author(s) Harald Hoyer and others
Initial release July 2009 (2009-07)
Stable release
048 / 6 July 2018 (2018-07-06)
Written in C, Unix shell
Operating system Linux
Platform Linux kernel
Type Initramfs
License GPL-2+ and LGPL-2+
Website dracut.wiki.kernel.org

dracut is an event-driven initramfs infrastructure. dracut (the tool) is used to create an initramfs image by copying tools and files from an installed system and combining it with the dracut framework, usually found in /usr/lib/dracut/modules.d.

Unlike existing initramfses, dracut's framework attempts to have as little hard-coded into the initramfs as possible. The initramfs has (basically) one purpose in life—mounting the root file system so the boot process can transition to the real rootfs. This is all driven off of device availability. Therefore, instead of having hard-coded scripts to do various things, dracut's initramfs depends on udev to create symbolic links to device nodes and when the rootfs's device node appears, it mounts it and switches root to it. This helps to keep the time required in initramfs down so that things like a 5-second boot are not made impossible as a result of the very existence of an initramfs.[1]

Most of the initramfs generation functionality in dracut is provided by generator modules that are sourced by the main dracut tool to install specific functionality into the initramfs. They live in the modules subdirectory, and use functionality provided by dracut-functions to do their work.[1]

Currently, dracut supports booting from btrfs, DM RAID, MD RAID, LVM2, device mapper multipath I/O, dm-crypt, cifs, FCoE, iSCSI, NBD and NFS.[2]

Lately dracut gained the ability to use systemd as process 1 in the initramfs.[3]

Adoption

dracut is available from the official repository of most distros, including

dracut is the default initramfs creation tool on openSUSE and many others.

References

  1. 1 2 dracut Wiki, kernel.org, retrieved 2012-10-10
  2. ↑ dracut documentation, kernel.org, retrieved 2012-10-10
  3. ↑ Google+ blog about systemd in dracut, plus.google.com, retrieved 2012-10-10
  4. ↑ Features/Dracut, FedoraProject, retrieved 2012-10-10
  5. ↑ RHEL6 SRPMS FTP, redhat.com, retrieved 2012-10-10
  6. ↑ Dracut - Gentoo Wiki, wiki.gentoo.org, retrieved 2012-10-10
  7. ↑ Package: dracut (005-1), debian.org, retrieved 2012-10-10
  8. ↑ dracut-010-6-mdv2011.0.noarch.rpm, pkgs.org, retrieved 2012-10-10
  9. ↑ Kernel
  10. ↑ Mageia App Db, mageia.madb.org, retrieved 2012-10-10
  11. ↑ openSUSE 13.2 Major features, openSUSE project, retrieved 2014-11-04
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