systemd/SOURCES/0478-man-describe-naming-schemes-in-a-new-man-page.patch
2021-09-10 05:03:39 +00:00

523 lines
27 KiB
Diff
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

From af528dcffaab1efea760395cc6676fe4b01e89b5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Thu, 9 May 2019 12:34:30 +0200
Subject: [PATCH] man: describe naming schemes in a new man page
I decided to make this a separate man page because it is freakin' long.
This content could equally well go in systemd-udevd.service(8), systemd.link(5),
or a new man page for the net_id builtin.
v2:
- rename to systemd.net-naming-scheme
- add udevadm test-builtin net_id example
(cherry picked from commit 0b1e5b6ed8c6b9a2bc53709eb75e381d360f05bf)
Related: #1827462
[msekleta: I've removed parts that describe features which are not
available in RHEL-8]
---
man/rules/meson.build | 1 +
man/systemd-udevd.service.xml | 19 +-
man/systemd.link.xml | 10 +-
man/systemd.net-naming-scheme.xml | 385 ++++++++++++++++++++++++++++++
src/udev/udev-builtin-net_id.c | 1 +
5 files changed, 402 insertions(+), 14 deletions(-)
create mode 100644 man/systemd.net-naming-scheme.xml
diff --git a/man/rules/meson.build b/man/rules/meson.build
index 7ae94ea265..e6c0a99bbd 100644
--- a/man/rules/meson.build
+++ b/man/rules/meson.build
@@ -714,6 +714,7 @@ manpages = [
['systemd.kill', '5', [], ''],
['systemd.link', '5', [], ''],
['systemd.mount', '5', [], ''],
+ ['systemd.net-naming-scheme', '7', [], ''],
['systemd.netdev', '5', [], 'ENABLE_NETWORKD'],
['systemd.network', '5', [], 'ENABLE_NETWORKD'],
['systemd.nspawn', '5', [], ''],
diff --git a/man/systemd-udevd.service.xml b/man/systemd-udevd.service.xml
index b738591c93..f4cdb2f1e7 100644
--- a/man/systemd-udevd.service.xml
+++ b/man/systemd-udevd.service.xml
@@ -174,15 +174,11 @@
<term><varname>net.naming-scheme=</varname></term>
<listitem>
<para>Network interfaces are renamed to give them predictable names when possible (unless
- <varname>net.ifnames=0</varname> is specified, see above). The names are derived from various
- device metadata fields. Newer versions of <filename>systemd-udevd.service</filename> take more of
- these fields into account, improving (and thus possibly changing) the names used for the same
- devices. With this kernel command line option it is possible to pick a specific version of this
- algorithm. It expects a naming scheme identifier as argument. Currently the following identifiers
- are known: <literal>rhel-8.0</literal>, <literal>rhel-8.1</literal>, <literal>rhel-8.2</literal>,
- <literal>rhel-8.3</literal> which each implement the naming scheme that was the default in the
- indicated Red Hat Enterprise Linux minor version. In addition, <literal>latest</literal> may be
- used to designate the latest scheme known (to this particular version of
+ <varname>net.ifnames=0</varname> is specified, see above). With this kernel command line option it
+ is possible to pick a specific version of this algorithm and override the default chosen at
+ compilation time. Expects one of the naming scheme identifiers listed in
+ <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ or <literal>latest</literal> to select the latest scheme known (to this particular version of
<filename>systemd-udevd.service</filename>).</para>
<para>Note that selecting a specific scheme is not sufficient to fully stabilize interface naming:
the naming is generally derived from driver attributes exposed by the kernel. As the kernel is
@@ -191,9 +187,8 @@
</listitem>
</varlistentry>
</variablelist>
- <!-- when adding entries here, consider also adding them
- in kernel-command-line.xml -->
- </refsect1>
+ <!-- when adding entries here, consider also adding them in kernel-command-line.xml -->
+ </refsect1>
<refsect1>
<title>See Also</title>
diff --git a/man/systemd.link.xml b/man/systemd.link.xml
index 6708753e82..32657308d0 100644
--- a/man/systemd.link.xml
+++ b/man/systemd.link.xml
@@ -286,6 +286,7 @@
<para>The name is set based on information given by
the firmware for on-board devices, as exported by the
udev property <literal>ID_NET_NAME_ONBOARD</literal>.
+ See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
</para>
</listitem>
</varlistentry>
@@ -295,6 +296,7 @@
<para>The name is set based on information given by
the firmware for hot-plug devices, as exported by the
udev property <literal>ID_NET_NAME_SLOT</literal>.
+ See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
</para>
</listitem>
</varlistentry>
@@ -303,7 +305,9 @@
<listitem>
<para>The name is set based on the device's physical
location, as exported by the udev property
- <literal>ID_NET_NAME_PATH</literal>.</para>
+ <literal>ID_NET_NAME_PATH</literal>.
+ See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+ </para>
</listitem>
</varlistentry>
<varlistentry>
@@ -311,7 +315,9 @@
<listitem>
<para>The name is set based on the device's persistent
MAC address, as exported by the udev property
- <literal>ID_NET_NAME_MAC</literal>.</para>
+ <literal>ID_NET_NAME_MAC</literal>.
+ See <citerefentry><refentrytitle>systemd.net-naming-scheme</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+ </para>
</listitem>
</varlistentry>
</variablelist>
diff --git a/man/systemd.net-naming-scheme.xml b/man/systemd.net-naming-scheme.xml
new file mode 100644
index 0000000000..a12cc3c460
--- /dev/null
+++ b/man/systemd.net-naming-scheme.xml
@@ -0,0 +1,385 @@
+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
+
+<refentry id="systemd.net-naming-scheme">
+ <refentryinfo>
+ <title>systemd.net-naming-scheme</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>systemd.net-naming-scheme</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>systemd.net-naming-scheme</refname>
+ <refpurpose>Network device naming schemes</refpurpose>
+ </refnamediv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>Network interfaces may be renamed to give them predictable names when there's enough information to
+ generate appropriate names and the use of certain types of names is configured. This page describes the
+ first part, i.e. what possible names may be generated. Those names are generated by the
+ <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ builtin <command>net_id</command> and exported as udev properties
+ (<varname>ID_NET_NAME_ONBOARD=</varname>, <varname>ID_NET_LABEL_ONBOARD=</varname>,
+ <varname>ID_NET_NAME_PATH=</varname>, <varname>ID_NET_NAME_SLOT=</varname>).</para>
+
+ <para>Names are derived from various device metadata attributes. Newer versions of udev take more of
+ these attributes into account, improving (and thus possibly changing) the names used for the same
+ devices. Differents version of the naming rules are called "naming schemes". The default naming scheme is
+ chosen at compilation time. Usually this will be the latest implemented version, but it is also possible
+ to set one of the older versions to preserve compatibility. This may be useful for example for
+ distributions, which may introduce new versions of systemd in stable releases without changing the naming
+ scheme. The naming scheme may also be overriden using the <varname>net.naming-scheme=</varname> kernel
+ command line switch, see
+ <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
+ Available naming schemes are described below.</para>
+
+ <para>After the udev proprties have been generated, appropriate udev rules may be used to actually rename
+ devices based on those properties. See the description of <varname>NamePolicy=</varname> in
+ <citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </para>
+ </refsect1>
+
+ <refsect1>
+ <title>Naming</title>
+
+ <para>All names start with a two-character prefix that signifies the interface type.</para>
+
+ <table>
+ <title>Two character prefixes based on the type of interface</title>
+
+ <tgroup cols='2'>
+ <thead>
+ <row>
+ <entry>Prefix</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry><constant>en</constant></entry>
+ <entry>Ethernet</entry>
+ </row>
+ <row>
+ <entry><constant>sl</constant></entry>
+ <entry>serial line IP (slip)</entry>
+ </row>
+ <row>
+ <entry><constant>wl</constant></entry>
+ <entry>Wireless local area network (WLAN)</entry>
+ </row>
+ <row>
+ <entry><constant>ww</constant></entry>
+ <entry>Wireless wide area network (WWAN)</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para>The udev <command>net_id</command> builtin exports the following udev device properties:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><varname>ID_NET_NAME_ONBOARD=<replaceable>prefix</replaceable><constant>o</constant><replaceable>number</replaceable></varname></term>
+
+ <listitem><para>This name is set based on the ordering information given by the firmware for
+ on-board devices. The name consists of the prefix, letter <constant>o</constant>, and a number
+ specified by the firmware. This is only available for PCI devices.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>ID_NET_LABEL_ONBOARD=<replaceable>prefix</replaceable> <replaceable>label</replaceable></varname></term>
+
+ <listitem><para>This property is set based on label given by the firmware for on-board devices. The
+ name consists of the prefix concatenated with the label. This is only available for PCI devices.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>ID_NET_NAME_MAC=<replaceable>prefix</replaceable><constant>x</constant><replaceable>AABBCCDDEEFF</replaceable></varname></term>
+
+ <listitem><para>This name consists of the prefix, letter <constant>x</constant>, and 12 hexadecimal
+ digits of the MAC address. It is available if the device has a fixed MAC address. Because this name
+ is based on an attribute of the card itself, it remains "stable" when the device is moved (even
+ between machines), but will change when the hardware is replaced.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>ID_NET_NAME_SLOT=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]</varname></term>
+ <term><varname>ID_NET_NAME_SLOT=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>b</constant><replaceable>number</replaceable></varname></term>
+ <term><varname>ID_NET_NAME_SLOT=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>u</constant><replaceable>port</replaceable>…[<constant>c</constant><replaceable>config</replaceable>][<constant>i</constant><replaceable>interface</replaceable>]</varname></term>
+ <term><varname>ID_NET_NAME_SLOT=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>v</constant><replaceable>slot</replaceable></varname></term>
+
+ <listitem><para>This property describes the slot position. Different schemes are used depending on
+ the bus type, as described in the table below. In all cases, PCI slot information must be known. In
+ case of USB, BCMA, and SR-VIO devices, the full name consists of the prefix, PCI slot identifier,
+ and USB or BCMA or SR-VIO slot identifier. The first two parts are denoted as "…" in the table
+ below.</para>
+
+ <table>
+ <title>Slot naming schemes</title>
+
+ <tgroup cols='2'>
+ <thead>
+ <row>
+ <entry>Format</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry><replaceable>prefix</replaceable> [<constant>P</constant><replaceable>domain</replaceable>] <constant>s</constant><replaceable>slot</replaceable> [<constant>f</constant><replaceable>function</replaceable>] [<constant>n</constant><replaceable>port_name</replaceable> | <constant>d</constant><replaceable>dev_port</replaceable>]</entry>
+ <entry>PCI slot number</entry>
+ </row>
+
+ <row>
+ <entry>… <constant>b</constant><replaceable>number</replaceable></entry>
+ <entry>Broadcom bus (BCMA) core number</entry>
+ </row>
+
+ <row>
+ <entry>… <constant>u</constant><replaceable>port</replaceable>… [<constant>c</constant><replaceable>config</replaceable>] [<constant>i</constant><replaceable>interface</replaceable>]</entry>
+ <entry>USB port number chain</entry>
+ </row>
+
+ <row>
+ <entry>… <constant>v</constant><replaceable>slot</replaceable></entry>
+ <entry>SR-VIO slot number</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para>The PCI domain is only prepended when it is not 0. All multi-function PCI devices will carry
+ the <constant>f<replaceable>function</replaceable></constant> number in the device name, including
+ the function 0 device. For non-multi-function devices, the number is suppressed if 0. The port name
+ <replaceable>port_name</replaceable> is used, or the port number
+ <constant>d</constant><replaceable>dev_port</replaceable> if the name is not known.</para>
+
+ <para>For BCMA devices, the core number is suppressed when 0.</para>
+
+ <para>For USB devices the full chain of port numbers of hubs is composed. If the name gets longer
+ than the maximum number of 15 characters, the name is not exported. The usual USB configuration
+ number 1 and interface number 0 values are suppressed.</para>
+ </listitem>
+
+ <para>SR-IOV virtual devices are named based on the name of the parent interface, with a suffix of
+ <constant>v</constant> and the virtual device number, with any leading zeros removed. The bus
+ number is ignored. This device type is found in IBM PowerVMs.</para>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable><constant>c</constant><replaceable>bus_id</replaceable></varname></term>
+ <term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable><constant>a</constant><replaceable>vendor</replaceable><replaceable>model</replaceable><constant>i</constant><replaceable>instance</replaceable></varname></term>
+ <term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable><constant>i</constant><replaceable>address</replaceable><constant>n</constant><replaceable>port_name</replaceable></varname></term>
+ <term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>p</constant><replaceable>bus</replaceable><constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>phys_port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]</varname></term>
+ <term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>p</constant><replaceable>bus</replaceable><constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>phys_port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>b</constant><replaceable>number</replaceable></varname></term>
+ <term><varname>ID_NET_NAME_PATH=<replaceable>prefix</replaceable>[<constant>P</constant><replaceable>domain</replaceable>]<constant>p</constant><replaceable>bus</replaceable><constant>s</constant><replaceable>slot</replaceable>[<constant>f</constant><replaceable>function</replaceable>][<constant>n</constant><replaceable>phys_port_name</replaceable>|<constant>d</constant><replaceable>dev_port</replaceable>]<constant>u</constant><replaceable>port</replaceable>…[<constant>c</constant><replaceable>config</replaceable>][<constant>i</constant><replaceable>interface</replaceable>]</varname></term>
+
+ <listitem><para>This property describes the device installation location. Different schemes are
+ used depending on the bus type, as described in the table below. For BCMA and USB devices, PCI path
+ information must known, and the full name consists of the prefix, PCI slot identifier, and USB or
+ BCMA location. The first two parts are denoted as "…" in the table below.</para>
+
+ <table>
+ <title>Path naming schemes</title>
+
+ <tgroup cols='2'>
+ <thead>
+ <row>
+ <entry>Format</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry><replaceable>prefix</replaceable> <constant>c</constant><replaceable>bus_id</replaceable></entry>
+ <entry>CCW or grouped CCW device identifier</entry>
+ </row>
+
+ <row>
+ <entry><replaceable>prefix</replaceable> <constant>a</constant><replaceable>vendor</replaceable> <replaceable>model</replaceable> <constant>i</constant><replaceable>instance</replaceable></entry>
+ <entry>ACPI path names for ARM64 platform devices</entry>
+ </row>
+
+ <row>
+ <entry><replaceable>prefix</replaceable> [<constant>P</constant><replaceable>domain</replaceable>] <constant>p</constant><replaceable>bus</replaceable> <constant>s</constant><replaceable>slot</replaceable> [<constant>f</constant><replaceable>function</replaceable>] [<constant>n</constant><replaceable>phys_port_name</replaceable> | <constant>d</constant><replaceable>dev_port</replaceable>]</entry>
+ <entry>PCI geographical location</entry>
+ </row>
+
+ <row>
+ <entry>… <constant>b</constant><replaceable>number</replaceable></entry>
+ <entry>Broadcom bus (BCMA) core number</entry>
+ </row>
+
+ <row>
+ <entry>… <constant>u</constant><replaceable>port</replaceable>… [<constant>c</constant><replaceable>config</replaceable>] [<constant>i</constant><replaceable>interface</replaceable>]</entry>
+ <entry>USB port number chain</entry>
+ </row>
+
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para>CCW and grouped CCW devices are found in IBM System Z mainframes. Any leading zeros and
+ dots are suppressed.</para>
+
+ <para>For PCI, BCMA, and USB devices, the same rules as described above for slot naming are
+ used.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>History</title>
+
+ <para>The following "naming schemes" have been defined:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>rhel-8.0</constant></term>
+
+ <listitem><para>Naming was changed for virtual network interfaces created with SR-IOV and NPAR and
+ for devices where the PCI network controller device does not have a slot number associated.</para>
+
+ <para>SR-IOV virtual devices are named based on the name of the parent interface, with a suffix of
+ <literal>v<replaceable>port</replaceable></literal>, where <replaceable>port</replaceable> is the
+ virtual device number. Previously those virtual devices were named as if completely independent.
+ </para>
+
+ <para>The ninth and later NPAR virtual devices are named following the scheme used for the first
+ eight NPAR partitions. Previously those devices were not renamed and the kernel default
+ ("eth<replaceable>N</replaceable>") was used.</para>
+
+ <para>Names are also generated for PCI devices where the PCI network controller device does not
+ have an associated slot number itself, but one of its parents does. Previously those devices were
+ not renamed and the kernel default was used.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>rhel-8.1</constant></term>
+
+ <para>Same as naming scheme <constant>rhel-8.0</constant>.</para>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>rhel-8.2</constant></term>
+
+ <para>Same as naming scheme <constant>rhel-8.0</constant>.</para>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>rhel-8.3</constant></term>
+
+ <para>Same as naming scheme <constant>rhel-8.0</constant>.</para>
+ </varlistentry>
+
+ <para>Note that <constant>latest</constant> may be used to denote the latest scheme known (to this
+ particular version of systemd.</para>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
+ <example>
+ <title>Using <command>udevadm test-builtin</command> to display device properties</title>
+
+ <programlisting>$ udevadm test-builtin net_id /sys/class/net/enp0s31f6
+...
+Using default interface naming scheme 'rhel-8.3'.
+ID_NET_NAMING_SCHEME=rhel-8.3
+ID_NET_NAME_MAC=enx54ee75cb1dc0
+ID_OUI_FROM_DATABASE=Wistron InfoComm(Kunshan)Co.,Ltd.
+ID_NET_NAME_PATH=enp0s31f6
+...</programlisting>
+ </example>
+
+ <example>
+ <title>PCI Ethernet card with firmware index "1"</title>
+
+ <programlisting>ID_NET_NAME_ONBOARD=eno1
+ID_NET_NAME_ONBOARD_LABEL=enEthernet Port 1
+ </programlisting>
+ <!-- FIXME: nuke the prefix! -->
+ </example>
+
+ <example>
+ <title>PCI Ethernet card in hotplug slot with firmware index number</title>
+
+ <programlisting># /sys/devices/pci0000:00/0000:00:1c.3/0000:05:00.0/net/ens1
+ID_NET_NAME_MAC=enx000000000466
+ID_NET_NAME_PATH=enp5s0
+ID_NET_NAME_SLOT=ens1</programlisting>
+ </example>
+
+ <example>
+ <title>PCI Ethernet multi-function card with 2 ports</title>
+
+ <programlisting># /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/enp2s0f0
+ID_NET_NAME_MAC=enx78e7d1ea46da
+ID_NET_NAME_PATH=enp2s0f0
+
+# /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.1/net/enp2s0f1
+ID_NET_NAME_MAC=enx78e7d1ea46dc
+ID_NET_NAME_PATH=enp2s0f1</programlisting>
+ </example>
+
+ <example>
+ <title>PCI WLAN card</title>
+
+ <programlisting># /sys/devices/pci0000:00/0000:00:1c.1/0000:03:00.0/net/wlp3s0
+ID_NET_NAME_MAC=wlx0024d7e31130
+ID_NET_NAME_PATH=wlp3s0</programlisting>
+ </example>
+
+ <example>
+ <title>USB built-in 3G modem</title>
+
+ <programlisting># /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.4/2-1.4:1.6/net/wwp0s29u1u4i6
+ID_NET_NAME_MAC=wwx028037ec0200
+ID_NET_NAME_PATH=wwp0s29u1u4i6</programlisting>
+ </example>
+
+ <example>
+ <title>USB Android phone</title>
+
+ <programlisting># /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.2/2-1.2:1.0/net/enp0s29u1u2
+ID_NET_NAME_MAC=enxd626b3450fb5
+ID_NET_NAME_PATH=enp0s29u1u2</programlisting>
+ </example>
+
+ <example>
+ <title>s390 grouped CCW interface</title>
+
+ <programlisting># /sys/devices/css0/0.0.0007/0.0.f5f0/group_device/net/encf5f0
+ID_NET_NAME_MAC=enx026d3c00000a
+ID_NET_NAME_PATH=encf5f0</programlisting>
+ </example>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>udevadm</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <ulink url="https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames">the
+ original page describing stable interface names</ulink>
+ </para>
+ </refsect1>
+
+</refentry>
diff --git a/src/udev/udev-builtin-net_id.c b/src/udev/udev-builtin-net_id.c
index d85dc2848b..aa553d5ade 100644
--- a/src/udev/udev-builtin-net_id.c
+++ b/src/udev/udev-builtin-net_id.c
@@ -78,6 +78,7 @@
* /sys/devices/css0/0.0.0007/0.0.f5f0/group_device/net/encf5f0
* ID_NET_NAME_MAC=enx026d3c00000a
* ID_NET_NAME_PATH=encf5f0
+ * When the code here is changed, man/systemd.net-naming-scheme.xml must be updated too.
*/
#include <errno.h>