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[[!meta copyright="Copyright © 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
2010 Free Software Foundation, Inc."]]
[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
id="license" text="Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version 1.2 or
any later version published by the Free Software Foundation; with no Invariant
Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
is included in the section entitled [[GNU Free Documentation
License|/fdl]]."]]"""]]
[[!meta title="What Is the GNU Hurd?"]]
The Hurd is the GNU project's replacement for the [[UNIX]] system's [[kernel]].
There are several
[[free software operating systems|https://www.gnu.org/distros/free-distros.en.html]]
using the [[Linux kernel|https://en.wikipedia.org/wiki/Linux_kernel]]. The
Hurd is an alternate operating system that uses a different kernel. You can
read more about the status of the Hurd [[here|hurd/status]]. If you decide
to use the Hurd, then we would recommend
[[the Debian GNU/Hurd distribution|https://www.debian.org/ports/hurd/]].
The Hurd is firstly a collection of protocols formalizing how different
components may interact. The protocols are designed to reduce the mutual
[[trust]] requirements of the actors thereby permitting a more
[[extensible|extensibility]] system. These include interface definitions to
manipulate files and directories and to resolve path names. This allows any
process to implement a file system. The only requirement is that it have
access to its backing store and that the [[principal]] that started it own the
file system node to which it connects.
The Hurd is also a set of [[servers|translator]] that implement these
protocols. They include [[file systems|hurd/translator/ext2fs]], network
protocols and [[authentication|hurd/translator/auth]].
The servers run on top of the [[microkernel/Mach]] [[microkernel]] and use
Mach's [[microkernel/mach/IPC]] mechanism to transfer information.
The Hurd provides a compatibility layer such that compiling higher level
programs is essentially transparent; that is, by means of the [[glibc]], it
provides the same standard interfaces known from other [[UNIX]]-like systems.
Thus, for a typical user, the Hurd is intended to silently work in the
background providing the services and infrastructure which the [[microkernel]]
itself has no business implementing, but that are required for higher level
programs and libraries to operate. Let's look at an example.
[[!img open_issues/images/overview.svg]]
Firefox invokes glibc's `send ()`, which in turn uses the pfinet (or
lwip) TCP/IP stack, which talk to our device drivers (rump or netdde),
which can actually access the hardware without entering kernel space
(GNU Mach). That's a lot of power for userspace!
The Hurd supplies the last major software component needed for a complete
[[GNU_operating_system|running/gnu]] as originally conceived by Richard
M. Stallman (RMS) in 1983. The GNU vision directly drove the creation and has
guided the evolution of the [Free Software Foundation](http://fsf.org/), the
organization that is the home of the [GNU project](http://gnu.org/gnu/).
The Hurd development effort is a somewhat separate project from the
[[Debian_GNU/Hurd|hurd/running/debian]] port.
Want to know what the Hurd can do? Read the [[status|hurd/status]] page.
Read about what the GNU Hurd is [[gramatically_speaking]].
Read about the [[origin_of_the_name]].
Want to read more [[Hurd documentation|hurd/documentation]]?
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