systemd Developer Tom Gundersen teg@jklm.no systemd-networkd.service 8 systemd-networkd.service systemd-networkd Network manager systemd-networkd.service /usr/lib/systemd/systemd-networkd systemd-networkd is a system service that manages networks. It detects and configures network devices as they appear, as well as creating virtual network devices. To configure low-level link settings independently of networks, see udev7 . Network configurations applied before networkd is started are not removed, and static configuration applied by networkd are not removed when networkd exits. This ensures restarting networkd does not cut the network connection, and, in particular, that it is safe to transition between the initrd and the real root, and back. The configuration files are read from the files located in the system network directory /usr/lib/systemd/network, the volatile runtime network directory /run/systemd/network and the local administration network directory /etc/systemd/network. All configuration files are collectively sorted and processed in lexical order, regardless of the directories in which they live. However, files with identical filenames replace each other. Files in /etc have the highest priority, files in /run take precedence over files with the same name in /usr/lib. This can be used to override a system-supplied configuration file with a local file if needed; a symlink in /etc with the same name as a configuration file in /usr/lib, pointing to /dev/null, disables the configuration file entirely. Virtual Network Device files must have the extension .netdev; other extensions are ignored. Virtual network devices are created as soon as networkd is started. A virtual network device is only created if the [Match] section matches the current environment, or if the section is empty. The following keys are accepted: Host Matches against the hostname or machine ID of the host. See ConditionHost= in systemd.unit5 for details. Virtualization Checks whether the system is executed in a virtualized environment and optionally test whether it is a specific implementation. See ConditionVirtualization= in systemd.unit5 for details. KernelCommandLine Checks whether a specific kernel command line option is set (or if prefixed with the exclamation mark unset). See ConditionKernelCommandLine= in systemd.unit5 for details. The [NetDev] section accepts the following keys: Name The interface name used when creating the bridge. This option is compulsory. Kind The netdev kind. Currently, bridge, bond and vlan are supported. This option is compulsory. The [VLAN] section only applies for netdevs of kind vlan, and accepts the following key: Id The VLAN ID to use. An integer in the range 0–4094. This option is compulsory. Network files must have the extension .network; other extensions are ignored. Networks are applied to links whenever the links appear. The network file contains a [Match] section, which determines if a given network file may be applied to a given device; and a [Network] section specifying how the device should be configured. The first (in lexical order) of the network files that matches a given device is applied. A network file is said to match a device if each of the entries in the [Match] section matches, or if the section is empty. The following keys are accepted: MACAddress The hardware address. Path The persistent path, as exposed by the udev property ID_PATH. May contain shell style globs. Driver The driver currently bound to the device, as exposed by the udev property DRIVER of its parent device. Type The device type, as exposed by the udev property DEVTYPE. Name The device name, as exposed by the udev property INTERFACE. May contain shell style globs. Host Matches against the hostname or machine ID of the host. See ConditionHost= in systemd.unit5 for details. Virtualization Checks whether the system is executed in a virtualized environment and optionally test whether it is a specific implementation. See ConditionVirtualization= in systemd.unit5 for details. KernelCommandLine Checks whether a specific kernel command line option is set (or if prefixed with the exclamation mark unset). See ConditionKernelCommandLine= in systemd.unit5 for details. The [Network] section accepts the following keys: Description A description of the device. This is only used for presentation purposes. DHCP A boolean. When true, enables basic DHCPv4 support. Address A static IPv4 or IPv6 address and its prefix length, separated by a / character. The format of the address must be as described in inet_pton3 . This is a short-hand for an [Address] section only containing an Address key (see below). Gateway The gateway address, which must be in the format described in inet_pton3 . This is a short-hand for a [Route] section only containing a Gateway key. DNS A DNS server address, which must be in the format described in inet_pton3 . Bridge The name of the bridge to add the link to. Bond The name of the bond to add the link to. VLAN The name of a VLAN to create on the link. This option may be specified more than once. The [Address] section accepts the following keys: Address As in the [Network] section. This key is mandatory. Broadcast The broadcast address, which must be in the format described in inet_pton3 . This key only applies to IPv4 addresses. If it is not given, it is derived from the Address key. Label An address label. The [Route] section accepts the following keys: Gateway As in the [Network] section. This key is mandatory. Destination The destination prefix of the route. Possibly followed by a slash and the prefixlength, if ommitted a full-length host route is assumed. The [DHCPv4] section accepts the following keys: UseDNS When true (the default), the DNS servers received from the DHCP server will be used and take precedence over any statically configured ones. UseMTU When true, the interface maximum transmission unit from the DHCP server will be used on the current link. Defaults to false. UseHostname When true (the default), the hostname received from the DHCP server will be used as the transient hostname. CriticalConnection When true, the connection will never be torn down even if the DHCP lease expires. This is contrary to the DHCP specification, but may be the best choice if, say, the root filesystem relies on this connection. Defaults to false. systemd1, udev7,