SYSTEMD.LINK(5)                            systemd.link                           SYSTEMD.LINK(5)



NAME
       systemd.link - Network device configuration

SYNOPSIS
       link.link

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
       /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 /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 /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; and 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.

[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.

       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, or if that is not set, the driver as exposed by "ethtool -i" of the
           device itself.

       Type=
           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.

           "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
           commandline. 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". The available policies are:

           "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

SEE ALSO
       systemd-udevd.service(8), udevadm(8)



systemd 215                                                                       SYSTEMD.LINK(5)