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67 lines
2.6 KiB
67 lines
2.6 KiB
<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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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 naming scheme</link>
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to assign names to network interfaces. This means that by default
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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 change</link>.
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If this is undesirable, for example if you have a single ethernet
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card, you can revert to the traditional scheme by 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 better to
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assign custom names based on the device hardware address. For
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example, we assign the name <literal>wan</literal> to the interface
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with MAC address <literal>52:54:00:12:01:01</literal> using a
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netword link unit:
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</para>
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<programlisting>
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<link linkend="opt-systemd.network.links">systemd.network.links."10-wan"</link> = {
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matchConfig.MACAddress = "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 networkd</emphasis>,
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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>
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<link linkend="opt-services.udev.initrdRules">services.udev.initrdRules</link> = ''
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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><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 avoid race
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conditions with other programs controlling the interface.
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</para></warning>
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</section>
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</section>
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