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 udev(7) .
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.
The "[NetDev]
" section accepts the following
keys:
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
".
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
".
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_pton(3)
. 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_pton(3) . 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_pton(3) .
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_pton(3)
. 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:
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.