NAME¶
systemd.link - Network device configuration
DESCRIPTION¶
Network link configuration is performed by the
net_setup_link udev builtin.
The link 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. Link files must have the extension .link;
other extensions are ignored. All link 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 link file with a local file if needed; a symlink in /etc
with the same name as a link file in /usr/lib, pointing to /dev/null,
disables the link file entirely.
The link file contains a "[Match]" section, which
determines if a given link file may be applied to a given device, as well as
a "[Link]" section specifying how the device should be configured.
The first (in lexical order) of the link files that matches a given device
is applied. Note that a default file 99-default.link is shipped by the
system, any user-supplied .link should hence have a lexically earlier name
to be considered at all.
[MATCH] SECTION OPTIONS¶
A link 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.
OriginalName=
A whitespace-separated list of shell-style globs matching
the device name, as exposed by the udev property "INTERFACE". This
can not be used to match on names that have already been changed from
userspace. Caution is advised when matching on kernel-assigned names, as they
are known to be unstable between reboots.
Path=
A whitespace-separated list of shell-style globs matching
the persistent path, as exposed by the udev property
"ID_PATH".
Driver=
A whitespace-separated list of shell-style globs matching
the driver currently bound to the device, as exposed by the udev property
"DRIVER" of its parent device, or if that is not set, the driver as
exposed by "ethtool -i" of the device itself.
Type=
A whitespace-separated list of shell-style globs matching
the device type, as exposed by the udev property "DEVTYPE".
Host=
Matches against the hostname or machine ID of the host.
See "ConditionHost=" in
systemd.unit(5) 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.unit(5) 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.unit(5) for
details.
Architecture=
Checks whether the system is running on a specific
architecture. See "ConditionArchitecture=" in
systemd.unit(5)
for details.
[LINK] SECTION OPTIONS¶
The "[Link]" section accepts the following keys:
Description=
A description of the device.
Alias=
The "ifalias" is set to this value.
MACAddressPolicy=
The policy by which the MAC address should be set. The
available policies are:
"persistent"
If the hardware has a persistent MAC address, as most
hardware should, and if it is used by the kernel, nothing is done. Otherwise,
a new MAC address is generated which is guaranteed to be the same on every
boot for the given machine and the given device, but which is otherwise
random. This feature depends on ID_NET_NAME_* properties existing for the
link, on hardware where these properties are not set the generation of a
persistent MAC address will fail.
"random"
If the kernel is using a random MAC address, nothing is
done. Otherwise, a new address is randomly generated each time the device
appears, typically at boot.
MACAddress=
The MAC address to use, if no
"MACAddressPolicy=" is specified.
NamePolicy=
An ordered, space-separated list of policies by which the
interface name should be set. "NamePolicy" may be disabled by
specifying "net.ifnames=0" on the kernel command line. Each of the
policies may fail, and the first successful one is used. The name is not set
directly, but is exported to udev as the property "ID_NET_NAME",
which is, by default, used by a udev rule to set "NAME". If the name
has already been set by userspace, no renaming is performed. The available
policies are:
"kernel"
If the kernel claims that the name it has set for a
device is predictable, then no renaming is performed.
"database"
The name is set based on entries in the udev's Hardware
Database with the key "ID_NET_NAME_FROM_DATABASE".
"onboard"
The name is set based on information given by the
firmware for on-board devices, as exported by the udev property
"ID_NET_NAME_ONBOARD".
"slot"
The name is set based on information given by the
firmware for hot-plug devices, as exported by the udev property
"ID_NET_NAME_SLOT".
"path"
The name is set based on the device's physical location,
as exported by the udev property "ID_NET_NAME_PATH".
"mac"
The name is set based on the device's persistent MAC
address, as exported by the udev property "ID_NET_NAME_MAC".
Name=
The interface name to use in case all the policies
specified in NamePolicy= fail, or in case NamePolicy= is missing
or disabled.
MTUBytes=
The maximum transmission unit in bytes to set for the
device. The usual suffixes K, M, G, are supported and are understood to the
base of 1024.
BitsPerSecond=
The speed to set for the device, the value is rounded
down to the nearest Mbps. The usual suffixes K, M, G, are supported and are
understood to the base of 1000.
Duplex=
The duplex mode to set for the device. The accepted
values are "half" and "full".
WakeOnLan=
The Wake-on-LAN policy to set for the device. The
supported values are:
"phy"
Wake on PHY activity.
"magic"
Wake on receipt of a magic packet.
"off"
Never wake.
EXAMPLE¶
Example 1. /etc/systemd/network/wireless.link
[Match]
MACAddress=12:34:56:78:9a:bc
Driver=brcmsmac
Path=pci-0000:02:00.0-*
Type=wlan
Virtualization=no
Host=my-laptop
Architecture=x86-64
[Link]
Name=wireless0
MTUBytes=1450
BitsPerSecond=10M
WakeOnLan=magic
MACAddress=cb:a9:87:65:43:21