12bab91d3b
For reliably identifying network interfaces, `PermanentMACAddress` is likely to be preferable to `MACAddress`. NetworkManager in particular commonly changes the MAC address of wireless interfaces. Reference: - https://www.freedesktop.org/software/systemd/man/systemd.link.html#PermanentMACAddress=
62 lines
2.7 KiB
XML
62 lines
2.7 KiB
XML
<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-rename-ifs">
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<title>Renaming network interfaces</title>
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<para>
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NixOS uses the udev
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<link xlink:href="https://systemd.io/PREDICTABLE_INTERFACE_NAMES/">predictable
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naming scheme</link> to assign names to network interfaces. This
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means that by default cards are not given the traditional names like
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<literal>eth0</literal> or <literal>eth1</literal>, whose order can
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change unpredictably across reboots. Instead, relying on physical
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locations and firmware information, the scheme produces names like
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<literal>ens1</literal>, <literal>enp2s0</literal>, etc.
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</para>
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<para>
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These names are predictable but less memorable and not necessarily
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stable: for example installing new hardware or changing firmware
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settings can result in a
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<link xlink:href="https://github.com/systemd/systemd/issues/3715#issue-165347602">name
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change</link>. If this is undesirable, for example if you have a
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single ethernet card, you can revert to the traditional scheme by
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setting
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<xref linkend="opt-networking.usePredictableInterfaceNames" /> to
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<literal>false</literal>.
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</para>
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<section xml:id="sec-custom-ifnames">
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<title>Assigning custom names</title>
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<para>
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In case there are multiple interfaces of the same type, it’s
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better to assign custom names based on the device hardware
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address. For example, we assign the name <literal>wan</literal> to
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the interface with MAC address
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<literal>52:54:00:12:01:01</literal> using a netword link unit:
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</para>
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<programlisting language="bash">
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systemd.network.links."10-wan" = {
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matchConfig.PermanentMACAddress = "52:54:00:12:01:01";
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linkConfig.Name = "wan";
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};
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</programlisting>
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<para>
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Note that links are directly read by udev, <emphasis>not
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networkd</emphasis>, and will work even if networkd is disabled.
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</para>
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<para>
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Alternatively, we can use a plain old udev rule:
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</para>
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<programlisting language="bash">
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services.udev.initrdRules = ''
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SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", \
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ATTR{address}=="52:54:00:12:01:01", KERNEL=="eth*", NAME="wan"
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'';
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</programlisting>
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<warning>
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<para>
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The rule must be installed in the initrd using
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<literal>services.udev.initrdRules</literal>, not the usual
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<literal>services.udev.extraRules</literal> option. This is to
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avoid race conditions with other programs controlling the
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interface.
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</para>
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</warning>
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</section>
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</section>
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