systemd/man/systemd-networkd.service.xml
Tom Gundersen 3a67e927e3 networkd-wait-online: improve interoptability and enable by default
To make sure we don't delay boot on systems where (some) network links are managed by someone else
we don't block if something else has successfully brought up a link.

We will still block until all links we are aware of that are  managed by networkd have been
configured, but if no such links exist, and someone else have configured a link sufficiently
that it has a carrier, it may be that the link is ready so we should no longer block.

Note that in all likelyhood the link is not ready (no addresses/routes configured),
so whatever network managment daemon configured it should provide a similar wait-online
service to block network-online.target until it is ready.

The aim is to block as long as we know networking is not fully configured, but no longer. This
will allow systemd-networkd-wait-online.service to be enabled on any system, even if we don't
know whether networkd is the main/only network manager.

Even in the case networking is fully configured by networkd, the default behavior may not be
sufficient: if two links need to be configured, but the first is fully configured before the
second one appears we will assume the network is up. To work around that, we allow specifying
specific devices to wait for before considering the network up.

This unit is enabled by default, just like systemd-networkd, but will only be pulled in if
anyone pulls in network-online.target.
2014-04-24 00:23:07 +02:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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<refentry id="systemd-networkd.service" conditional='ENABLE_NETWORKD'>
<refentryinfo>
<title>systemd-networkd.service</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Tom</firstname>
<surname>Gundersen</surname>
<email>teg@jklm.no</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-networkd.service</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-networkd.service</refname>
<refname>systemd-networkd</refname>
<refpurpose>Network manager</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>systemd-networkd.service</filename></para>
<para><filename>/usr/lib/systemd/systemd-networkd</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>systemd-networkd</command> is a system
service that manages networks. It detects and configures
network devices as they appear, as well as creating virtual
network devices.</para>
<para>To configure low-level link settings independently of
networks, see
<citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>
.</para>
<para>Network configurations applied before networkd is started
are not removed, and static configuration applied by networkd
is not removed when networkd exits. Dynamic configuration applied by
networkd may also optionally be left in place on shut-down. This ensures
restarting networkd does not cut the network connection, and, in particular,
that it is safe to transition between the initrd and the real root,
and back.</para>
<para>Nameservers configured in networkd, or received over DHCP
are exposed in <filename>/run/systemd/network/resolv.conf</filename>.
This file should not be used directly, but only through a symlink
from <filename>/etc/resolv.conf</filename>.</para>
</refsect1>
<refsect1><title>Configuration Files</title>
<para>The configuration files are read from the files located in the
system network directory <filename>/usr/lib/systemd/network</filename>,
the volatile runtime network directory
<filename>/run/systemd/network</filename> and the local administration
network directory <filename>/etc/systemd/network</filename>.</para>
<para>Networks are configured in <filename>.network</filename> files, see
<citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
and virtual network devices are configured in <filename>.netdev</filename> files, see
<citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.link</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.netdev</refentrytitle><manvolnum>5</manvolnum></citerefentry>
<citerefentry><refentrytitle>systemd-network-wait-online.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>