Dracut is a set of tools that provide enhanced functionality for automating the

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...

boot process In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so s ...

. The tool named is used to create a Linux boot image (

initramfs In Linux systems, initrd (''initial ramdisk'') is a scheme for loading a temporary root file system into memory, to be used as part of the Linux startup process. initrd and initramfs refer to two different methods of achieving this. Both are comm ...

) by copying tools and files from an installed system and combining it with the Dracut framework, which is usually found in . Unlike existing Linux

boot image A boot image is a type of disk image (a computer file containing the complete contents and structure of a storage medium). When it is transferred onto a boot device it allows the associated hardware to boot. The ''boot image'' usually includes t ...

s, the Dracut framework attempts to introduce as little hard-coded logic into the initramfs as possible. The initramfs has essentially one purpose: locating and mounting the real

root file system In a computer file system, and primarily used in the Unix and Unix-like operating systems, the root directory is the first or top-most directory in a hierarchy. It can be likened to the trunk of a tree, as the starting point where all branche ...

so that the boot process can transition to it. This functionality is dependent on device availability. Therefore, instead of having hard-coded

scripts Script may refer to: Writing systems * Script, a distinctive writing system, based on a repertoire of specific elements or symbols, or that repertoire * Script (styles of handwriting) ** Script typeface, a typeface with characteristics of handw ...

to determine device availability and suitability, Dracut's initramfs depends on the Linux device manager (

udev udev (userspace ) is a device manager for the Linux kernel. As the successor of devfsd and hotplug, udev primarily manages device nodes in the directory. At the same time, udev also handles all user space events raised when hardware devices ...

) to create

symbolic link In computing, a symbolic link (also symlink or soft link) is a file whose purpose is to point to a file or directory (called the "target") by specifying a path thereto. Symbolic links are supported by POSIX and by most Unix-like operating syste ...

s to

device node A device is usually a constructed tool. Device may also refer to: Technology Computing * Device, a colloquial term encompassing desktops, laptops, tablets, smartphones, etc. * Device file, an interface of a device driver * Peripheral, any devic ...

s. When the root file system's device node appears, Dracut mounts it as the new root file system. This helps to minimize the time required in initramfs so that things like a 5-second boot are now made possible. Most of the initramfs generation functionality in Dracut is provided by generator modules that are sourced by the main tool to install specific functionality into the initramfs. They live in the modules

subdirectory In computing, a directory is a file system cataloging structure which contains references to other computer files, and possibly other directories. On many computers, directories are known as folders, or drawers, analogous to a workbench or the ...

, and use functionality provided by dracut-functions to do their work. Currently, dracut supports booting from

ext2 The ext2 or second extended file system is a file system for the Linux kernel. It was initially designed by French software developer Rémy Card as a replacement for the extended file system (ext). Having been designed according to the same ...

ext3 ext3, or third extended filesystem, is a journaled file system that is commonly used by the Linux kernel. It used to be the default file system for many popular Linux distributions. Stephen Tweedie first revealed that he was working on ext ...

ext4 ext4 (fourth extended filesystem) is a journaling file system for Linux, developed as the successor to ext3. ext4 was initially a series of backward-compatible extensions to ext3, many of them originally developed by Cluster File Systems for ...

btrfs Btrfs (pronounced as "better F S", "butter F S", "b-tree F S", or simply by spelling it out) is a computer storage format that combines a file system based on the copy-on-write (COW) principle with a logical volume manager (not to be confused ...

ISO_9660 ISO 9660 (also known as ECMA-119) is a file system for optical disc media. Being sold by the International Organization for Standardization (ISO) the file system is considered an international technical standard. Since the specification is ...

, DM RAID, MD RAID, LVM2, device mapper multipath I/O,

dm-crypt dm-crypt is a transparent block device encryption subsystem in Linux kernel versions 2.6 and later and in DragonFly BSD. It is part of the device mapper (dm) infrastructure, and uses cryptographic routines from the kernel's Crypto API. Unlike it ...

cifs Server Message Block (SMB) is a communication protocol originally developed in 1983 by Barry A. Feigenbaum at IBM and intended to provide shared access to files and printers across nodes on a network of systems running IBM's OS/2. It also provide ...

, FCoE,

iSCSI Internet Small Computer Systems Interface or iSCSI ( ) is an Internet Protocol-based storage networking standard for linking data storage facilities. iSCSI provides block-level access to storage devices by carrying SCSI commands over a TCP/IP ...

, NBD and NFS.

Adoption

Red Hat Red Hat, Inc. is an American software company that provides open source software products to enterprises. Founded in 1993, Red Hat has its corporate headquarters in Raleigh, North Carolina, with other offices worldwide. Red Hat has become a ...

is the original author of dracut. Red Hat-derived

Linux distribution A Linux distribution (often abbreviated as distro) is an operating system made from a software collection that includes the Linux kernel and, often, a package management system. Linux users usually obtain their operating system by downloading one ...

s use dracut for initramfs creation. Use outside Red Hat-derived distributions is limited. *

Fedora A fedora () is a hat with a soft brim and indented crown.Kilgour, Ruth Edwards (1958). ''A Pageant of Hats Ancient and Modern''. R. M. McBride Company. It is typically creased lengthwise down the crown and "pinched" near the front on both side ...

since version 12, Constantine *

Red Hat Enterprise Linux Red Hat Enterprise Linux (RHEL) is a commercial open-source Linux distribution developed by Red Hat for the commercial market. Red Hat Enterprise Linux is released in server versions for x86-64, Power ISA, ARM64, and IBM Z and a desktop ...

since version 6 *

openSUSE openSUSE () is a free and open source RPM-based Linux distribution developed by the openSUSE project. The initial release of the community project was a beta version of SUSE Linux 10.0. Additionally the project creates a variety of tools, s ...

since version 13.2, when it became the default initramfs creation tool *

SUSE Linux Enterprise Server SUSE Linux Enterprise (often abbreviated to SLE) is a Linux-based operating system developed by SUSE. It is available in two editions, suffixed with Server (SLES) for servers and mainframes, and Desktop (SLED) for workstations and desktop com ...

since version 12 *

Void Linux Void Linux is an independent Linux distribution that uses the X Binary Package System (XBPS) package manager, which was designed and implemented from scratch, and the runit init system. Excluding binary kernel blobs, a base install is composed e ...

OpenMandriva Lx OpenMandriva Lx is a Linux distribution forked from Mandriva Linux. It is maintained by the OpenMandriva Association. History Origin of the distribution OpenMandriva Lx is a community Linux distribution. Originally an offering of Mandriva Linux ...

, since it was Mandriva Linux in 2011 *

Mageia Mageia is a Linux-based operating system, distributed as free and open source software. It was forked from the Mandriva Linux distribution. The Greek term () means enchantment, fascination, glamour, wizardry. The first release of the soft ...

since Mageia 2 * Gentoo for distribution kernels since 2020, for custom kernels possible since 2010 * KaOS * Bottlerocket OS *

EndeavourOS EndeavourOS is a Linux distribution based on Arch Linux. EndeavourOS features the graphical Calamares installer capable of installing the Xfce, Budgie, Cinnamon, GNOME, i3, KDE Plasma 5, LXQt, and MATE desktop environments, the former of wh ...

Distributions which include dracut, but do not use it by default for initramfs creation: *

Debian Debian (), also known as Debian GNU/Linux, is a Linux distribution composed of free and open-source software, developed by the community-supported Debian Project, which was established by Ian Murdock on August 16, 1993. The first version of De ...

since version 6 (Squeeze) *

Arch Linux Arch Linux () is an independently developed, x86-64 general-purpose Linux distribution that strives to provide the latest stable versions of most software by following a rolling-release model. The default installation is a minimal base system, ...

in extra repository *

Ubuntu Linux Ubuntu ( ) is a Linux distribution based on Debian and composed mostly of free and open-source software. Ubuntu is officially released in three editions: '' Desktop'', ''Server'', and ''Core'' for Internet of things devices and robots. Al ...

since 18.04 Most other distributions have made dracut available as an optiona
package
to replace the distributions default initramfs generator.

References

External links

Dracut source files

Dracut manual page
{{Linux kernel Linux kernel

Adoption

See also

References

External links