SYSTEMD.LINK(5) systemd.link SYSTEMD.LINK(5)
NAME
systemd.link - Network device configuration
SYNOPSIS
link.link
DESCRIPTION
A plain ini-style text file that encodes configuration for matching
network devices, used by systemd-udevd(8) and in particular its
net_setup_link builtin. See systemd.syntax(7) for a general description
of the syntax.
Note that some distributions may incorporate .link files in their early
boot facilities (e.g. by including copies of the .link files in
initramfs). As such it may be necessary to take manual steps to ensure
that any local changes are consistent with early-boot storage
facilities. The relevant distribution-specific documentation should be
consulted.
The .link files are read from the files located in the system network
directory /usr/lib/systemd/network and /usr/local/lib/systemd/network
[1], 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
alphanumeric order, regardless of the directories in which they live.
However, files with identical filenames replace each other. It is
recommended that each filename is prefixed with a number smaller than
"70" (e.g. 10-eth0.link). Otherwise, the default .link files or those
generated by systemd-network-generator.service(8) may take precedence
over user configured files. 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. As a special case, an empty file (file size 0)
or symlink with the same name pointing to /dev/null disables the
configuration file entirely (it is "masked").
Along with the link file foo.link, a "drop-in" directory foo.link.d/ may
exist. All files with the suffix ".conf" from this directory will be
merged in the alphanumeric order and parsed after the main file itself
has been parsed. This is useful to alter or add configuration settings,
without having to modify the main configuration file. Each drop-in file
must have appropriate section headers.
In addition to /etc/systemd/network, drop-in ".d" directories can be
placed in /usr/lib/systemd/network or /run/systemd/network directories.
Drop-in files in /etc/ take precedence over those in /run/ which in turn
take precedence over those in /usr/lib/. Drop-in files under any of
these directories take precedence over the main link file wherever
located.
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.
See udevadm(8) for diagnosing problems with .link files.
[MATCH] SECTION OPTIONS
A link file is said to match an interface if all matches specified by
the [Match] section are satisfied. When a link file does not contain
valid settings in [Match] section, then the file will match all
interfaces and systemd-udevd warns about that. Hint: to avoid the
warning and to make it clear that all interfaces shall be matched, add
the following:
OriginalName=*
The first (in alphanumeric order) of the link files that matches a given
interface is applied, all later files are ignored, even if they match as
well. The following keys are accepted:
MACAddress=
A whitespace-separated list of hardware addresses. The acceptable
formats are:
colon-delimited hexadecimal
Each field must be one byte. E.g. "12:34:56:78:90:ab" or
"AA:BB:CC:DD:EE:FF".
Added in version 250.
hyphen-delimited hexadecimal
Each field must be one byte. E.g. "12-34-56-78-90-ab" or
"AA-BB-CC-DD-EE-FF".
Added in version 250.
dot-delimited hexadecimal
Each field must be two bytes. E.g. "1234.5678.90ab" or
"AABB.CCDD.EEFF".
Added in version 250.
IPv4 address format
E.g. "127.0.0.1" or "192.168.0.1".
Added in version 250.
IPv6 address format
E.g. "2001:0db8:85a3::8a2e:0370:7334" or "::1".
Added in version 250.
The total length of each MAC address must be 4 (for IPv4 tunnel), 6
(for Ethernet), 16 (for IPv6 tunnel), or 20 (for InfiniBand). This
option may appear more than once, in which case the lists are
merged. If the empty string is assigned to this option, the list of
hardware addresses defined prior to this is reset. Defaults to
unset.
Added in version 211.
PermanentMACAddress=
A whitespace-separated list of hardware's permanent addresses. While
MACAddress= matches the device's current MAC address, this matches
the device's permanent MAC address, which may be different from the
current one. Use full colon-, hyphen- or dot-delimited hexadecimal,
or IPv4 or IPv6 address format. This option may appear more than
once, in which case the lists are merged. If the empty string is
assigned to this option, the list of hardware addresses defined
prior to this is reset. Defaults to unset.
Added in version 245.
Path=
A whitespace-separated list of shell-style globs matching the
persistent path, as exposed by the udev property ID_PATH.
Added in version 211.
Driver=
A whitespace-separated list of shell-style globs matching the driver
currently bound to the device, as exposed by the udev property
ID_NET_DRIVER of its parent device, or if that is not set, the
driver as exposed by ethtool -i of the device itself. If the list is
prefixed with a "!", the test is inverted.
Added in version 211.
Type=
A whitespace-separated list of shell-style globs matching the device
type, as exposed by networkctl list. If the list is prefixed with a
"!", the test is inverted. Some valid values are "ether",
"loopback", "wlan", "wwan". Valid types are named either from the
udev "DEVTYPE" attribute, or "ARPHRD_" macros in linux/if_arp.h, so
this is not comprehensive.
Added in version 211.
Kind=
A whitespace-separated list of shell-style globs matching the device
kind, as exposed by networkctl status INTERFACE or ip -d link show
INTERFACE. If the list is prefixed with a "!", the test is inverted.
Some valid values are "bond", "bridge", "gre", "tun", "veth". Valid
kinds are given by netlink's "IFLA_INFO_KIND" attribute, so this is
not comprehensive.
Added in version 251.
Property=
A whitespace-separated list of udev property names with their values
after equals sign ("="). If multiple properties are specified, the
test results are ANDed. If the list is prefixed with a "!", the test
is inverted. If a value contains white spaces, then please quote
whole key and value pair. If a value contains quotation, then please
escape the quotation with "\".
Example: if a .link file has the following:
Property=ID_MODEL_ID=9999 "ID_VENDOR_FROM_DATABASE=vendor name" "KEY=with \"quotation\""
then, the .link file matches only when an interface has all the
above three properties.
Added in version 243.
OriginalName=
A whitespace-separated list of shell-style globs matching the device
name, as exposed by the udev property "INTERFACE". This cannot 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.
Added in version 218.
Host=
Matches against the hostname or machine ID of the host. See
ConditionHost= in systemd.unit(5) for details. When prefixed with an
exclamation mark ("!"), the result is negated. If an empty string is
assigned, the previously assigned value is cleared.
Added in version 211.
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. When
prefixed with an exclamation mark ("!"), the result is negated. If
an empty string is assigned, the previously assigned value is
cleared.
Added in version 211.
KernelCommandLine=
Checks whether a specific kernel command line option is set. See
ConditionKernelCommandLine= in systemd.unit(5) for details. When
prefixed with an exclamation mark ("!"), the result is negated. If
an empty string is assigned, the previously assigned value is
cleared.
Added in version 211.
KernelVersion=
Checks whether the kernel version (as reported by uname -r) matches
a certain expression. See ConditionKernelVersion= in systemd.unit(5)
for details. When prefixed with an exclamation mark ("!"), the
result is negated. If an empty string is assigned, the previously
assigned value is cleared.
Added in version 237.
Credential=
Checks whether the specified credential was passed to the
systemd-udevd.service service. See System and Service Credentials[2]
for details. When prefixed with an exclamation mark ("!"), the
result is negated. If an empty string is assigned, the previously
assigned value is cleared.
Added in version 252.
Architecture=
Checks whether the system is running on a specific architecture. See
ConditionArchitecture= in systemd.unit(5) for details. When prefixed
with an exclamation mark ("!"), the result is negated. If an empty
string is assigned, the previously assigned value is cleared.
Added in version 211.
Firmware=
Checks whether the system is running on a machine with the specified
firmware. See ConditionFirmware= in systemd.unit(5) for details.
When prefixed with an exclamation mark ("!"), the result is negated.
If an empty string is assigned, the previously assigned value is
cleared.
Added in version 249.
[LINK] SECTION OPTIONS
The [Link] section accepts the following keys:
Description=
A description of the device.
Added in version 211.
Property=
Set specified udev properties. This takes space separated list of
key-value pairs concatenated with equal sign ("="). Example:
Property=HOGE=foo BAR=baz
This option supports simple specifier expansion, see the Specifiers
section below. This option can be specified multiple times. If an
empty string is assigned, then the all previous assignments are
cleared.
This setting is useful to configure the "ID_NET_MANAGED_BY="
property which declares which network management service shall
manage the interface, which is respected by systemd-networkd(8) and
others. Use
Property=ID_NET_MANAGED_BY=io.systemd.Network
to declare explicitly that systemd-networkd shall manage the
interface, or set the property to something else to declare
explicitly it shall not do so. See systemd.network(5) for details
how this property is used to match interface names.
Added in version 256.
ImportProperty=
Import specified udev properties from the saved database. This takes
space separated list of property names. Example:
ImportProperty=HOGE BAR
This option supports simple specifier expansion, see the Specifiers
section below. This option can be specified multiple times. If an
empty string is assigned, then the all previous assignments are
cleared.
If the same property is also set in Property= in the above, then the
imported property value will be overridden by the value specified in
Property=.
Added in version 256.
UnsetProperty=
Unset specified udev properties. This takes space separated list of
property names. Example:
UnsetProperty=HOGE BAR
This option supports simple specifier expansion, see the Specifiers
section below. This option can be specified multiple times. If an
empty string is assigned, then the all previous assignments are
cleared.
This setting is applied after ImportProperty= and Property= are
applied. Hence, if the same property is specified in ImportProperty=
or Property=, then the imported or specified property value will be
ignored, and the property will be unset.
Added in version 256.
Alias=
The ifalias interface property is set to this value.
Added in version 211.
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 to exist for the link. On hardware
where these properties are not set, the generation of a
persistent MAC address will fail.
Added in version 211.
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. Either way, the random
address will have the "unicast" and "locally administered" bits
set.
Added in version 211.
none
Keeps the MAC address assigned by the kernel. Or use the MAC
address specified in MACAddress=.
Added in version 227.
An empty string assignment is equivalent to setting "none".
Added in version 211.
MACAddress=
The interface MAC address to use. For this setting to take effect,
MACAddressPolicy= must either be unset, empty, or "none".
Added in version 211.
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(7), rule to set NAME. 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.
Added in version 216.
database
The name is set based on entries in the udev's Hardware Database
with the key ID_NET_NAME_FROM_DATABASE.
Added in version 211.
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. See systemd.net-naming-scheme(7).
Added in version 211.
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. See systemd.net-naming-scheme(7).
Added in version 211.
path
The name is set based on the device's physical location, as
exported by the udev property ID_NET_NAME_PATH. See systemd.net-
naming-scheme(7).
Added in version 211.
mac
The name is set based on the device's persistent MAC address, as
exported by the udev property ID_NET_NAME_MAC. See systemd.net-
naming-scheme(7).
Added in version 211.
keep
If the device already had a name given by userspace (as part of
creation of the device or a rename), keep it.
Added in version 241.
Added in version 211.
Name=
The interface name to use. This option has lower precedence than
NamePolicy=, so for this setting to take effect, NamePolicy= must
either be unset, empty, disabled, or all policies configured there
must fail. Also see the example below with "Name=dmz0".
Note that specifying a name that the kernel might use for another
interface (for example "eth0") is dangerous because the name
assignment done by udev will race with the assignment done by the
kernel, and only one interface may use the name. Depending on the
order of operations, either udev or the kernel will win, making the
naming unpredictable. It is best to use some different prefix, for
example "internal0"/"external0" or "lan0"/"lan1"/"lan3".
Interface names must have a minimum length of 1 character and a
maximum length of 15 characters, and may contain any 7bit ASCII
character, with the exception of control characters, ":", "/" and
"%". While "." is an allowed character, it is recommended to avoid
it when naming interfaces as various tools (such as resolvconf(1))
use it as separator character. Also, fully numeric interface names
are not allowed (in order to avoid ambiguity with interface
specification by numeric indexes), nor are the special strings ".",
"..", "all" and "default".
Added in version 211.
AlternativeNamesPolicy=
A space-separated list of policies by which the interface's
alternative names should be set. Each of the policies may fail, and
all successful policies are used. The available policies are
"database", "onboard", "slot", "path", and "mac". If the kernel does
not support the alternative names, then this setting will be
ignored.
Added in version 245.
AlternativeName=
The alternative interface name to use. This option can be specified
multiple times. If the empty string is assigned to this option, the
list is reset, and all prior assignments have no effect. If the
kernel does not support the alternative names, then this setting
will be ignored.
Alternative interface names may be used to identify interfaces in
various tools. In contrast to the primary name (as configured with
Name= above) there may be multiple alternative names referring to
the same interface. Alternative names may have a maximum length of
127 characters, in contrast to the 15 allowed for the primary
interface name, but otherwise are subject to the same naming
constraints.
Added in version 245.
TransmitQueues=
Specifies the device's number of transmit queues. An integer in the
range 1...4096. When unset, the kernel's default will be used.
Added in version 248.
ReceiveQueues=
Specifies the device's number of receive queues. An integer in the
range 1...4096. When unset, the kernel's default will be used.
Added in version 248.
TransmitQueueLength=
Specifies the transmit queue length of the device in number of
packets. An unsigned integer in the range 0...4294967294. When
unset, the kernel's default will be used.
Added in version 248.
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.
Added in version 211.
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.
Added in version 211.
Duplex=
The duplex mode to set for the device. The accepted values are half
and full.
Added in version 211.
AutoNegotiation=
Takes a boolean. If set to yes, automatic negotiation of
transmission parameters is enabled. Autonegotiation is a procedure
by which two connected ethernet devices choose common transmission
parameters, such as speed, duplex mode, and flow control. When
unset, the kernel's default will be used.
Note that if autonegotiation is enabled, speed and duplex settings
are read-only. If autonegotiation is disabled, speed and duplex
settings are writable if the driver supports multiple link modes.
Added in version 233.
WakeOnLan=
The Wake-on-LAN policy to set for the device. Takes the special
value "off" which disables Wake-on-LAN, or space separated list of
the following words:
phy
Wake on PHY activity.
Added in version 211.
unicast
Wake on unicast messages.
Added in version 235.
multicast
Wake on multicast messages.
Added in version 235.
broadcast
Wake on broadcast messages.
Added in version 235.
arp
Wake on ARP.
Added in version 235.
magic
Wake on receipt of a magic packet.
Added in version 211.
secureon
Enable SecureOn password for MagicPacket. Implied when
WakeOnLanPassword= is specified. If specified without
WakeOnLanPassword= option, then the password is read from the
credential "LINK.link.wol.password" (e.g.,
"60-foo.link.wol.password"), and if the credential not found,
then read from "wol.password". See
ImportCredential=/LoadCredential=/SetCredential= in
systemd.exec(5) for details. The password in the credential,
must be 6 bytes in hex format with each byte separated by a
colon (":") like an Ethernet MAC address, e.g.,
"aa:bb:cc:dd:ee:ff".
Added in version 235.
Defaults to unset, and the device's default will be used. This
setting can be specified multiple times. If an empty string is
assigned, then the all previous assignments are cleared.
Added in version 211.
WakeOnLanPassword=
Specifies the SecureOn password for MagicPacket. Takes an absolute
path to a regular file or an AF_UNIX stream socket, or the plain
password. When a path to a regular file is specified, the password
is read from it. When an AF_UNIX stream socket is specified, a
connection is made to it and the password is read from it. The
password must be 6 bytes in hex format with each byte separated by a
colon (":") like an Ethernet MAC address, e.g., "aa:bb:cc:dd:ee:ff".
This implies WakeOnLan=secureon. Defaults to unset, and the current
value will not be changed.
Added in version 250.
Port=
The port option is used to select the device port. The supported
values are:
tp
An Ethernet interface using Twisted-Pair cable as the medium.
Added in version 234.
aui
Attachment Unit Interface (AUI). Normally used with hubs.
Added in version 234.
bnc
An Ethernet interface using BNC connectors and co-axial cable.
Added in version 234.
mii
An Ethernet interface using a Media Independent Interface (MII).
Added in version 234.
fibre
An Ethernet interface using Optical Fibre as the medium.
Added in version 234.
Added in version 234.
Advertise=
This sets what speeds and duplex modes of operation are advertised
for auto-negotiation. This implies "AutoNegotiation=yes". The
supported values are:
Table 1. Supported advertise values
┌────────────────────────────┬──────────────┬─────────────┐
│ Advertise │ Speed (Mbps) │ Duplex Mode │
├────────────────────────────┼──────────────┼─────────────┤
│ 10baset-full │ 10 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10baset1brr-full │ 10 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10baset1l-full │ 10 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10baset1s-full │ 10 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10baset-half │ 10 │ half │
├────────────────────────────┼──────────────┼─────────────┤
│ 10baset1s-half │ 10 │ half │
├────────────────────────────┼──────────────┼─────────────┤
│ 10baset1s-p2mp-half │ 10 │ half │
├────────────────────────────┼──────────────┼─────────────┤
│ 100basefx-full │ 100 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100baset-full │ 100 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100baset1-full │ 100 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100basefx-half │ 100 │ half │
├────────────────────────────┼──────────────┼─────────────┤
│ 100baset-half │ 100 │ half │
├────────────────────────────┼──────────────┼─────────────┤
│ 1000basekx-full │ 1000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 1000baset-full │ 1000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 1000baset1-full │ 1000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 1000basex-full │ 1000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 1000baset-half │ 1000 │ half │
├────────────────────────────┼──────────────┼─────────────┤
│ 2500baset-full │ 2500 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 2500basex-full │ 2500 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 5000baset-full │ 5000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10000baser-fec │ 10000 │ │
├────────────────────────────┼──────────────┼─────────────┤
│ 10000basecr-full │ 10000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10000baseer-full │ 10000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10000basekr-full │ 10000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10000basekx4-full │ 10000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10000baselr-full │ 10000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10000baselrm-full │ 10000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10000basesr-full │ 10000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 10000baset-full │ 10000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 20000basekr2-full │ 20000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 20000basemld2-full │ 20000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 25000basecr-full │ 25000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 25000basekr-full │ 25000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 25000basesr-full │ 25000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 40000basecr4-full │ 40000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 40000basekr4-full │ 40000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 40000baselr4-full │ 40000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 40000basesr4-full │ 40000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 50000basecr-full │ 50000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 50000basecr2-full │ 50000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 50000basedr-full │ 50000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 50000basekr-full │ 50000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 50000basekr2-full │ 50000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 50000baselr-er-fr-full │ 50000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 50000basesr-full │ 50000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 50000basesr2-full │ 50000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 56000basecr4-full │ 56000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 56000basekr4-full │ 56000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 56000baselr4-full │ 56000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 56000basesr4-full │ 56000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basecr-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basecr2-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basecr4-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basedr-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basedr2-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basekr-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basekr2-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basekr4-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000baselr-er-fr-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000baselr2-er2-fr2-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000baselr4-er4-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basesr-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basesr2-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 100000basesr4-full │ 100000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basecr-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basecr2-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basecr4-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basedr-2-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basedr-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basedr2-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basedr4-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basekr-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basekr2-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basekr4-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000baselr2-er2-fr2-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000baselr4-er4-fr4-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basesr-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basesr2-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basesr4-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 200000basevr-full │ 200000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basecr2-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basecr4-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basecr8-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basedr2-2-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basedr2-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basedr4-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basedr8-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basekr2-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basekr4-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basekr8-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000baselr4-er4-fr4-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000baselr8-er8-fr8-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basesr2-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basesr4-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basesr8-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 400000basevr2-full │ 400000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basecr4-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basecr8-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basedr4-2-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basedr4-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basedr8-2-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basedr8-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basekr4-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basekr8-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basesr4-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basesr8-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basevr4-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ 800000basevr8-full │ 800000 │ full │
├────────────────────────────┼──────────────┼─────────────┤
│ asym-pause │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ aui │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ autonegotiation │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ backplane │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ bnc │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ fec-baser │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ fec-llrs │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ fec-none │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ fec-rs │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ fibre │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ mii │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ pause │ │ │
├────────────────────────────┼──────────────┼─────────────┤
│ tp │ │ │
└────────────────────────────┴──────────────┴─────────────┘
By default, this is unset, i.e. all possible modes will be
advertised. This option may be specified more than once, in which
case all specified speeds and modes are advertised. If the empty
string is assigned to this option, the list is reset, and all prior
assignments have no effect.
Added in version 240.
ReceiveChecksumOffload=
Takes a boolean. If set to true, hardware offload for checksumming
of ingress network packets is enabled. When unset, the kernel's
default will be used.
Added in version 245.
TransmitChecksumOffload=
Takes a boolean. If set to true, hardware offload for checksumming
of egress network packets is enabled. When unset, the kernel's
default will be used.
Added in version 245.
TCPSegmentationOffload=
Takes a boolean. If set to true, TCP Segmentation Offload (TSO) is
enabled. When unset, the kernel's default will be used.
Added in version 232.
TCP6SegmentationOffload=
Takes a boolean. If set to true, TCP6 Segmentation Offload
(tx-tcp6-segmentation) is enabled. When unset, the kernel's default
will be used.
Added in version 235.
GenericSegmentationOffload=
Takes a boolean. If set to true, Generic Segmentation Offload (GSO)
is enabled. When unset, the kernel's default will be used.
Added in version 232.
GenericReceiveOffload=
Takes a boolean. If set to true, Generic Receive Offload (GRO) is
enabled. When unset, the kernel's default will be used.
Added in version 232.
GenericReceiveOffloadHardware=
Takes a boolean. If set to true, hardware accelerated Generic
Receive Offload (GRO) is enabled. When unset, the kernel's default
will be used.
Added in version 250.
LargeReceiveOffload=
Takes a boolean. If set to true, Large Receive Offload (LRO) is
enabled. When unset, the kernel's default will be used.
Added in version 232.
ReceivePacketSteeringCPUMask=
Configures Receive Packet Steering (RPS) list of CPUs to which RPS
may forward traffic. Takes a list of CPU indices or ranges separated
by either whitespace or commas. Alternatively, takes the special
value "all", which will include all available CPUs in the mask. CPU
ranges are specified by the lower and upper CPU indices separated by
a dash (e.g. "2-6"). This option may be specified more than once,
in which case the specified list of CPU ranges are merged. If an
empty string is assigned, the list is reset, all assignments prior
to this will have no effect. Defaults to unset and RPS CPU list is
unchanged. To disable RPS when it was previously enabled, use the
special value "disable".
Added in version 256.
ReceiveVLANCTAGHardwareAcceleration=
Takes a boolean. If set to true, receive VLAN CTAG hardware
acceleration is enabled. When unset, the kernel's default will be
used.
Added in version 250.
TransmitVLANCTAGHardwareAcceleration=
Takes a boolean. If set to true, transmit VLAN CTAG hardware
acceleration is enabled. When unset, the kernel's default will be
used.
Added in version 250.
ReceiveVLANCTAGFilter=
Takes a boolean. If set to true, receive filtering on VLAN CTAGs is
enabled. When unset, the kernel's default will be used.
Added in version 250.
TransmitVLANSTAGHardwareAcceleration=
Takes a boolean. If set to true, transmit VLAN STAG hardware
acceleration is enabled. When unset, the kernel's default will be
used.
Added in version 250.
NTupleFilter=
Takes a boolean. If set to true, receive N-tuple filters and actions
are enabled. When unset, the kernel's default will be used.
Added in version 250.
RxChannels=, TxChannels=, OtherChannels=, CombinedChannels=
Specifies the number of receive, transmit, other, or combined
channels, respectively. Takes an unsigned integer in the range
1...4294967295 or "max". If set to "max", the advertised maximum
value of the hardware will be used. When unset, the number will not
be changed. Defaults to unset.
Added in version 239.
RxBufferSize=, RxMiniBufferSize=, RxJumboBufferSize=, TxBufferSize=
Specifies the maximum number of pending packets in the NIC receive
buffer, mini receive buffer, jumbo receive buffer, or transmit
buffer, respectively. Takes an unsigned integer in the range
1...4294967295 or "max". If set to "max", the advertised maximum
value of the hardware will be used. When unset, the number will not
be changed. Defaults to unset.
Added in version 244.
RxFlowControl=
Takes a boolean. When set, enables receive flow control, also known
as the ethernet receive PAUSE message (generate and send ethernet
PAUSE frames). When unset, the kernel's default will be used.
Added in version 246.
TxFlowControl=
Takes a boolean. When set, enables transmit flow control, also known
as the ethernet transmit PAUSE message (respond to received ethernet
PAUSE frames). When unset, the kernel's default will be used.
Added in version 246.
AutoNegotiationFlowControl=
Takes a boolean. When set, auto negotiation enables the interface to
exchange state advertisements with the connected peer so that the
two devices can agree on the ethernet PAUSE configuration. When
unset, the kernel's default will be used.
Added in version 246.
GenericSegmentOffloadMaxBytes=
Specifies the maximum size of a Generic Segment Offload (GSO) packet
the device should accept. The usual suffixes K, M, G are supported
and are understood to the base of 1024. An unsigned integer in the
range 1...65536. Defaults to unset.
Added in version 248.
GenericSegmentOffloadMaxSegments=
Specifies the maximum number of Generic Segment Offload (GSO)
segments the device should accept. An unsigned integer in the range
1...65535. Defaults to unset.
Added in version 248.
UseAdaptiveRxCoalesce=, UseAdaptiveTxCoalesce=
Boolean properties that, when set, enable/disable adaptive Rx/Tx
coalescing if the hardware supports it. When unset, the kernel's
default will be used.
Added in version 250.
RxCoalesceSec=, RxCoalesceIrqSec=, RxCoalesceLowSec=,
RxCoalesceHighSec=, TxCoalesceSec=, TxCoalesceIrqSec=,
TxCoalesceLowSec=, TxCoalesceHighSec=
These properties configure the delay before Rx/Tx interrupts are
generated after a packet is sent/received. The "Irq" properties come
into effect when the host is servicing an IRQ. The "Low" and "High"
properties come into effect when the packet rate drops below the low
packet rate threshold or exceeds the high packet rate threshold
respectively if adaptive Rx/Tx coalescing is enabled. When unset,
the kernel's defaults will be used.
Added in version 250.
RxMaxCoalescedFrames=, RxMaxCoalescedIrqFrames=,
RxMaxCoalescedLowFrames=, RxMaxCoalescedHighFrames=,
TxMaxCoalescedFrames=, TxMaxCoalescedIrqFrames=,
TxMaxCoalescedLowFrames=, TxMaxCoalescedHighFrames=
These properties configure the maximum number of frames that are
sent/received before a Rx/Tx interrupt is generated. The "Irq"
properties come into effect when the host is servicing an IRQ. The
"Low" and "High" properties come into effect when the packet rate
drops below the low packet rate threshold or exceeds the high packet
rate threshold respectively if adaptive Rx/Tx coalescing is enabled.
When unset, the kernel's defaults will be used.
Added in version 250.
CoalescePacketRateLow=, CoalescePacketRateHigh=
These properties configure the low and high packet rate (expressed
in packets per second) threshold respectively and are used to
determine when the corresponding coalescing settings for low and
high packet rates come into effect if adaptive Rx/Tx coalescing is
enabled. If unset, the kernel's defaults will be used.
Added in version 250.
CoalescePacketRateSampleIntervalSec=
Configures how often to sample the packet rate used for adaptive
Rx/Tx coalescing. This property cannot be zero. This lowest time
granularity supported by this property is seconds. Partial seconds
will be rounded up before being passed to the kernel. If unset, the
kernel's default will be used.
Added in version 250.
StatisticsBlockCoalesceSec=
How long to delay driver in-memory statistics block updates. If the
driver does not have an in-memory statistic block, this property is
ignored. This property cannot be zero. If unset, the kernel's
default will be used.
Added in version 250.
MDI=
Specifies the medium dependent interface (MDI) mode for the
interface. A MDI describes the interface from a physical layer
implementation to the physical medium used to carry the
transmission. Takes one of the following words: "straight" (or
equivalently: "mdi"), "crossover" (or equivalently: "mdi-x",
"mdix"), and "auto". When "straight", the MDI straight through mode
will be used. When "crossover", the MDI crossover (MDI-X) mode will
be used. When "auto", the MDI status is automatically detected.
Defaults to unset, and the kernel's default will be used.
Added in version 251.
SR-IOVVirtualFunctions=
Specifies the number of SR-IOV virtual functions. Takes an integer
in the range 0...2147483647. Defaults to unset, and automatically
determined from the values specified in the VirtualFunction=
settings in the [SR-IOV] sections.
Added in version 251.
[SR-IOV] SECTION OPTIONS
SR-IOV provides the ability to partition a single physical PCI resource
into virtual PCI functions which can then be e.g. injected into a VM. In
the case of network VFs, SR-IOV reduces latency and CPU utilisation for
north-south network traffic (that is, traffic with endpoints outside the
host machine), by allowing traffic to bypass the host machine’s network
stack.
The presence of an [SR-IOV] section in a .link file will cause the
creation and configuration of the specified virtual function. Within a
.network file, the specified virtual function will be configured, but
must already exist. Specify several [SR-IOV] sections to configure
several SR-IOVs.
The [SR-IOV] section accepts the following keys.
VirtualFunction=
Specifies a Virtual Function (VF), lightweight PCIe function
designed solely to move data in and out. Takes an integer in the
range 0...2147483646. This option is compulsory.
Added in version 251.
VLANId=
Specifies VLAN ID of the virtual function. Takes an integer in the
range 1...4095.
Added in version 251.
QualityOfService=
Specifies quality of service of the virtual function. Takes an
integer in the range 1...4294967294.
Added in version 251.
VLANProtocol=
Specifies VLAN protocol of the virtual function. Takes "802.1Q" or
"802.1ad".
Added in version 251.
MACSpoofCheck=
Takes a boolean. Controls the MAC spoof checking. When unset, the
kernel's default will be used.
Added in version 251.
QueryReceiveSideScaling=
Takes a boolean. Toggle the ability of querying the receive side
scaling (RSS) configuration of the virtual function (VF). The VF RSS
information like RSS hash key may be considered sensitive on some
devices where this information is shared between VF and the physical
function (PF). When unset, the kernel's default will be used.
Added in version 251.
Trust=
Takes a boolean. Allows one to set trust mode of the virtual
function (VF). When set, VF users can set a specific feature which
may impact security and/or performance. When unset, the kernel's
default will be used.
Added in version 251.
LinkState=
Allows one to set the link state of the virtual function (VF). Takes
a boolean or a special value "auto". Setting to "auto" means a
reflection of the physical function (PF) link state, "yes" lets the
VF to communicate with other VFs on this host even if the PF link
state is down, "no" causes the hardware to drop any packets sent by
the VF. When unset, the kernel's default will be used.
Added in version 251.
MACAddress=
Specifies the MAC address for the virtual function.
Added in version 251.
SPECIFIERS
Some settings resolve specifiers which may be used to write generic unit
files referring to runtime or unit parameters that are replaced when the
unit files are loaded. Specifiers must be known and resolvable for the
setting to be valid. The following specifiers are understood:
Table 2. Specifiers available in unit files
┌───────────┬──────────────────────┬────────────────────────┐
│ Specifier │ Meaning │ Details │
├───────────┼──────────────────────┼────────────────────────┤
│ "%a" │ Architecture │ A short string │
│ │ │ identifying the │
│ │ │ architecture of the │
│ │ │ local system. A │
│ │ │ string such as x86, │
│ │ │ x86-64 or arm64. See │
│ │ │ the architectures │
│ │ │ defined for │
│ │ │ ConditionArchitecture= │
│ │ │ in systemd.unit(5) │
│ │ │ for a full list. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%A" │ Operating system │ The operating system │
│ │ image version │ image version │
│ │ │ identifier of the │
│ │ │ running system, as │
│ │ │ read from the │
│ │ │ IMAGE_VERSION= field │
│ │ │ of /etc/os-release. If │
│ │ │ not set, resolves to │
│ │ │ an empty string. See │
│ │ │ os-release(5) for more │
│ │ │ information. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%b" │ Boot ID │ The boot ID of the │
│ │ │ running system, │
│ │ │ formatted as string. │
│ │ │ See random(4) for more │
│ │ │ information. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%B" │ Operating system │ The operating system │
│ │ build ID │ build identifier of │
│ │ │ the running system, as │
│ │ │ read from the │
│ │ │ BUILD_ID= field of │
│ │ │ /etc/os-release. If │
│ │ │ not set, resolves to │
│ │ │ an empty string. See │
│ │ │ os-release(5) for more │
│ │ │ information. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%H" │ Host name │ The hostname of the │
│ │ │ running system. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%l" │ Short host name │ The hostname of the │
│ │ │ running system, │
│ │ │ truncated at the first │
│ │ │ dot to remove any │
│ │ │ domain component. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%m" │ Machine ID │ The machine ID of the │
│ │ │ running system, │
│ │ │ formatted as string. │
│ │ │ See machine-id(5) for │
│ │ │ more information. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%M" │ Operating system │ The operating system │
│ │ image identifier │ image identifier of │
│ │ │ the running system, as │
│ │ │ read from the │
│ │ │ IMAGE_ID= field of │
│ │ │ /etc/os-release. If │
│ │ │ not set, resolves to │
│ │ │ an empty string. See │
│ │ │ os-release(5) for more │
│ │ │ information. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%o" │ Operating system ID │ The operating system │
│ │ │ identifier of the │
│ │ │ running system, as │
│ │ │ read from the ID= │
│ │ │ field of │
│ │ │ /etc/os-release. See │
│ │ │ os-release(5) for more │
│ │ │ information. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%q" │ Pretty host name │ The pretty hostname of │
│ │ │ the running system, as │
│ │ │ read from the │
│ │ │ PRETTY_HOSTNAME= field │
│ │ │ of /etc/machine-info. │
│ │ │ If not set, resolves │
│ │ │ to the short hostname. │
│ │ │ See machine-info(5) │
│ │ │ for more information. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%T" │ Directory for │ This is either /tmp or │
│ │ temporary files │ the path "$TMPDIR", │
│ │ │ "$TEMP" or "$TMP" are │
│ │ │ set to. (Note that the │
│ │ │ directory may be │
│ │ │ specified without a │
│ │ │ trailing slash.) │
├───────────┼──────────────────────┼────────────────────────┤
│ "%v" │ Kernel release │ Identical to uname -r │
│ │ │ output. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%V" │ Directory for larger │ This is either │
│ │ and persistent │ /var/tmp or the path │
│ │ temporary files │ "$TMPDIR", "$TEMP" or │
│ │ │ "$TMP" are set to. │
│ │ │ (Note that the │
│ │ │ directory may be │
│ │ │ specified without a │
│ │ │ trailing slash.) │
├───────────┼──────────────────────┼────────────────────────┤
│ "%w" │ Operating system │ The operating system │
│ │ version ID │ version identifier of │
│ │ │ the running system, as │
│ │ │ read from the │
│ │ │ VERSION_ID= field of │
│ │ │ /etc/os-release. If │
│ │ │ not set, resolves to │
│ │ │ an empty string. See │
│ │ │ os-release(5) for more │
│ │ │ information. │
├───────────┼──────────────────────┼────────────────────────┤
│ "%W" │ Operating system │ The operating system │
│ │ variant ID │ variant identifier of │
│ │ │ the running system, as │
│ │ │ read from the │
│ │ │ VARIANT_ID= field of │
│ │ │ /etc/os-release. If │
│ │ │ not set, resolves to │
│ │ │ an empty string. See │
│ │ │ os-release(5) for more │
│ │ │ information. │
└───────────┴──────────────────────┴────────────────────────┘
EXAMPLES
Example 1. /usr/lib/systemd/network/99-default.link
The link file 99-default.link that is shipped with systemd defines the
default policies for the interface name, alternative names, and MAC
address of links.
[Match]
OriginalName=*
[Link]
NamePolicy=keep kernel database onboard slot path
AlternativeNamesPolicy=database onboard slot path
MACAddressPolicy=persistent
Example 2. /etc/systemd/network/10-dmz.link
This example assigns the fixed name "dmz0" to the interface with the MAC
address 00:a0:de:63:7a:e6:
[Match]
MACAddress=00:a0:de:63:7a:e6
[Link]
Name=dmz0
NamePolicy= is not set, so Name= takes effect. We use the "10-" prefix
to order this file early in the list. Note that it needs to be before
99-default.link, i.e. it needs a numerical prefix, to have any effect at
all.
Example 3. (Re-)applying a .link file to an interface
After a new .link file has been created, or an existing .link file
modified, the new settings may be applied to the matching interface with
the following commands:
$ sudo udevadm control --reload
$ sudo ip link set eth0 down
$ sudo udevadm trigger --verbose --settle --action add /sys/class/net/eth0
You may also need to stop the service that manages the network
interface, e.g. systemd-networkd.service(8) or NetworkManager.service
before the above operation, and then restart the service after that. For
more details about udevadm command, see udevadm(8).
Example 4. Debugging NamePolicy= assignments
$ sudo SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/hub0
...
Parsed configuration file /usr/lib/systemd/network/99-default.link
Parsed configuration file /etc/systemd/network/10-eth0.link
ID_NET_DRIVER=cdc_ether
Config file /etc/systemd/network/10-eth0.link applies to device hub0
link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
hub0: Device has name_assign_type=4
Using default interface naming scheme 'v240'.
hub0: Policies did not yield a name, using specified Name=hub0.
ID_NET_LINK_FILE=/etc/systemd/network/10-eth0.link
ID_NET_NAME=hub0
...
Explicit Name= configuration wins in this case.
sudo SYSTEMD_LOG_LEVEL=debug udevadm test-builtin net_setup_link /sys/class/net/enp0s31f6
...
Parsed configuration file /usr/lib/systemd/network/99-default.link
Parsed configuration file /etc/systemd/network/10-eth0.link
Created link configuration context.
ID_NET_DRIVER=e1000e
Config file /usr/lib/systemd/network/99-default.link applies to device enp0s31f6
link_config: autonegotiation is unset or enabled, the speed and duplex are not writable.
enp0s31f6: Device has name_assign_type=4
Using default interface naming scheme 'v240'.
enp0s31f6: Policy *keep*: keeping existing userspace name
enp0s31f6: Device has addr_assign_type=0
enp0s31f6: MAC on the device already matches policy *persistent*
ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
...
In this case, the interface was already renamed, so the keep policy
specified as the first option in 99-default.link means that the existing
name is preserved. If keep was removed, or if were in boot before the
renaming has happened, we might get the following instead:
enp0s31f6: Policy *path* yields "enp0s31f6".
enp0s31f6: Device has addr_assign_type=0
enp0s31f6: MAC on the device already matches policy *persistent*
ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
ID_NET_NAME=enp0s31f6
...
Please note that the details of output are subject to change.
Example 5. /etc/systemd/network/10-internet.link
This example assigns the fixed name "internet0" to the interface with
the device path "pci-0000:00:1a.0-*":
[Match]
Path=pci-0000:00:1a.0-*
[Link]
Name=internet0
Example 6. /etc/systemd/network/25-wireless.link
Here's an overly complex example that shows the use of a large number of
[Match] and [Link] settings.
[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
SEE ALSO
systemd-udevd.service(8), udevadm(8), systemd.netdev(5),
systemd.network(5), systemd-network-generator.service(8)
NOTES
1. 💣💥🧨💥💥💣 Please note that those configuration files must be available
at all times. If /usr/local/ is a separate partition, it may not be
available during early boot, and must not be used for configuration.
2. System and Service Credentials
https://systemd.io/CREDENTIALS
systemd 257.9 SYSTEMD.LINK(5)
Generated by dwww version 1.16 on Tue Dec 16 05:00:35 CET 2025.