NetworkManager is a daemon that sits on top of

libudev 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 a ...

and other Linux kernel interfaces (and a couple of other daemons) and provides a high-level interface for the configuration of the network interfaces.

Rationale

NetworkManager is a software utility that aims to simplify the use of

computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...

s. NetworkManager is available for

Linux kernel The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU ...

-based and other

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

How it works

Simplified Structure of the Linux Kernel

To connect computers with each other, various

communications protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synch ...

s have been developed, e.g.

IEEE 802.3 IEEE 802.3 is a working group and a collection standards defining the physical layer and data link layer's media access control (MAC) of wired Ethernet. The standards are produced by the working group of Institute of Electrical and Electronics ...

(Ethernet), IEEE 802.11 ("wireless"),

IEEE 802.15.1 Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limit ...

(Bluetooth),

PPPoE The Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol for encapsulating Point-to-Point Protocol (PPP) frames inside Ethernet frames. It appeared in 1999, in the context of the boom of DSL as the solution for tunneling pack ...

, PPPoA, and many many more. Each participating computer must have the suitable hardware, e.g. network card or wireless network card and this hardware must be configured accordingly to be able to establish a connection. In case of a monolithic kernel all the device drivers are part of it. The hardware is accessed (and also configured) through its device driver. In case of Linux, the kernel presents for each device driver a representation in form of a device file. All device files are found in the /dev directory, and traditionally the device files for Ethernet hardware have been named eth0, eth1, etc. Since systemd, they are named differently: enp4s0, etc. (This abstraction is called the

everything is a file Everything is a file is an idea that Unix, and its derivatives handle input/output to and from resources such as documents, hard-drives, modems, keyboards, printers and even some inter-process and network communications as simple streams of bytes ...

concept.) Anything in user-space accesses the hardware through its device file. The configuration utility to configure the hardware, and programs like the

web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used o ...

/ SSH/ NTP-client/etc. to send and receive network packets.

Configuration of network interfaces without NetworkManager

On Linux and all Unix-like operating systems, the utilities ifconfig and the newer ip (from the

iproute2 iproute2 is a collection of userspace utilities for controlling and monitoring various aspects of networking in the Linux kernel, including routing, network interfaces, tunnels, traffic control, and network-related device drivers. iproute2 ...

-bundle) are used to configure

and IEEE 802.11 hardware. These utilities configure the kernel directly and the configuration is applied immediately. After boot-up, the user is required to configure them again. To apply the same static configuration after each boot-up, the PID1-programs are used: System V init executes

shell script A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be scripting languages. Typical operations performed by shell scripts include file man ...

s and binary programs,

systemd systemd is a software suite that provides an array of system components for Linux operating systems. Its main aim is to unify service configuration and behavior across Linux distributions; Its primary component is a "system and service manag ...

parses its own conf-files (and executes programs). The boot-up configuration for network interfaces is stored in /etc/network/interfaces
/code> for Debian Linux distributions and its derivatives or ifcfg
/code> files in /etc/sysconfig/network-scripts/ for

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 ...

and its derivatives, and DNS-servers in /etc/resolv.conf. /etc/network/interfaces or /etc/sysconfig/network-scripts/ifcfg-* can define a static IP-address or dhclient
/code> to be used, and all kinds of VPN can be configured here as well. In case the configuration has to be changed,

DHCP The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a cli ...

-protocol goes a long way to do so automatically, without the user even noticing.

Configuration of network interfaces with NetworkManager

* NetworkManager is accessible via dbus. * Configuration is stored in /etc/NetworkManager/NetworkManager.conf However, dynamic configurations (i.e., not stored in a static configuration file but taken from outside the host, and potentially changing after boot) have been an increasingly more common configuration, especially as we've moved from physically large servers to more portable hosts that may be plugged and unplugged (or moved from WiFi hotspot to WiFi hotspot) at the will of the user. Bootp was an early protocol used for this, and to this day its descendant

is still very common. Many Unix-like systems include a program called dhclient to handle this dynamic configuration. Given a relatively static or simple dynamic configuration, static configuration modified by dhclient works well. However, as networks and their topologies get more complex, a central manager for all the network configuration information becomes more essential.

Software architecture

NetworkManager has two components: # the NetworkManager daemon, the actual software which manages connections and reports network changes # several graphical front-ends for diverse graphical desktop environments, such as

GNOME Shell GNOME Shell is the graphical shell of the GNOME desktop environment starting with version 3, which was released on April 6, 2011. It provides basic functions like launching applications, switching between windows and is also a widget engine. ...

, GNOME Panel, KDE Plasma Workspaces,

Cinnamon Cinnamon is a spice obtained from the inner bark of several tree species from the genus '' Cinnamomum''. Cinnamon is used mainly as an aromatic condiment and flavouring additive in a wide variety of cuisines, sweet and savoury dishes, breakf ...

, etc. Both components are intended by the developers to be reasonably portable, and the applet is available to

desktop environment In computing, a desktop environment (DE) is an implementation of the desktop metaphor made of a bundle of programs running on top of a computer operating system that share a common graphical user interface (GUI), sometimes described as a grap ...

s which implement the Freedesktop.org System Tray Protocol, including GNOME, KDE Plasma Workspaces,

Enlightenment (software) Enlightenment, also known simply as E, is a compositing window manager for the X Window System. Since version 20, Enlightenment is also a Wayland compositor. Enlightenment developers have referred to it as "the original eye-candy window manager ...

and Xfce. As the components communicate via D-Bus, applications can be written to be “ link-aware”, or to replace the provided applet entirely. One example is KNetworkManager, a KDE frontend to NetworkManager developed by

Novell Novell, Inc. was an American software and services company headquartered in Provo, Utah, that existed from 1980 until 2014. Its most significant product was the multi- platform network operating system known as Novell NetWare. Under the le ...

for SUSE Linux.

=Graphical front-ends and command line interfaces

= File:Network Manager 0.9.5.png, The GUI shows all available APs. The user merely needs to click on the desired one. File:GNOME Shell NM front-end 3.10.png, Graphical front-end for

3.10 ;nm-applet :nm-applet is the

GNOME A gnome is a mythological creature and diminutive spirit in Renaissance magic and alchemy, first introduced by Paracelsus in the 16th century and later adopted by more recent authors including those of modern fantasy literature. Its characte ...

applet In computing, an applet is any small application that performs one specific task that runs within the scope of a dedicated widget engine or a larger program, often as a plug-in. The term is frequently used to refer to a Java applet, a program ...

for NetworkManager. ;nmcli :nmcli is NetworkManager's built-in

command-line interface A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...

added in 2010. nmcli allows easy display of NetworkManager's current status, manage connections and devices, monitor connections. ;nmtui :nmtui is a built-in text-based user interface. nmtui is relatively basic compared to nmcli, which only allows users to add/edit a connection, activate a connection, and set the hostname of the system. ;cnetworkmanager :cnetworkmanager command-line interface for NetworkManager.

Mobile broadband configuration assistant

Antti Kaijanmäki announced the development of a mobile broadband configuration assistant for NetworkManager in April 2008; it became available in NetworkManager version 0.7.0. Together with the package mobile-broadband-provider-info the connection is easily configured.

History

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 ...

initiated the NetworkManager project in 2004 with the goal of enabling Linux users to deal more easily with modern networking needs, particularly

wireless networking A wireless network is a computer network that uses wireless data connections between network nodes. Wireless networking is a method by which homes, telecommunications networks and business installations avoid the costly process of introducing c ...

. NetworkManager takes an opportunistic approach to network selection, attempting to use the best available connection as outages occur, or as the user roams between wireless networks. It prefers

Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1 ...

connections over “known” wireless networks, which are preferred over wireless networks with SSIDs to which the user has never connected. The user is prompted for WEP or WPA keys as needed. The NetworkManager project was among the first major Linux desktop components to utilize

D-Bus In computing, D-Bus (short for "Desktop Bus") is a message-oriented middleware mechanism that allows communication between multiple processes running concurrently on the same machine. D-Bus was developed as part of the freedesktop.org project ...

and

HAL HAL may refer to: Aviation * Halali Airport (IATA airport code: HAL) Halali, Oshikoto, Namibia * Hawaiian Airlines (ICAO airline code: HAL) * HAL Airport, Bangalore, India * Hindustan Aeronautics Limited an Indian aerospace manufacturer of figh ...

extensively. Since June 2009, however, NetworkManager no longer depends on HAL, and since 0.9.10 (ca. 2014), neither does it require the D-Bus daemon to be running for root operation.

References

External links

NetworkManager Homepage

Service Provider Database

NetworkManager in freedesktop.org

Original NetworkManager page at redhat.com via WaybackMachine

How to use a WiFi interface with NetworkManager
{{DEFAULTSORT:Networkmanager Applications using D-Bus Free network-related software Linux network-related software Red Hat software