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mirror of https://github.com/systemd/systemd-stable.git synced 2024-12-22 13:33:56 +03:00

man: say explicitly that network.target should give the guarantee that synthetic network interfaces have been created

Prompted by: #18793
This commit is contained in:
Lennart Poettering 2021-02-25 14:35:47 +01:00
parent 26ac511a7e
commit 85f3bd23da

View File

@ -948,20 +948,29 @@
<varlistentry>
<term><filename>network.target</filename></term>
<listitem>
<para>This unit is supposed to indicate when network
functionality is available, but it is only very weakly
defined what that is supposed to mean, with one exception:
at shutdown, a unit that is ordered after
<filename>network.target</filename> will be stopped before
the network — to whatever level it might be set up then —
is shut down. It is hence useful when writing service files
that require network access on shutdown, which should order
themselves after this target, but not pull it in. Also see
<ulink url="https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running
Services After the Network is up</ulink> for more
information. Also see
<filename>network-online.target</filename> described
above.</para>
<para>This unit is supposed to indicate when network functionality is available, but it is only
very weakly defined what that is supposed to mean. However, the following should apply at
minimum:</para>
<itemizedlist>
<listitem><para>At start-up, any configured synthetic network devices (i.e. not physical ones
that require hardware to show up and be probed, but virtual ones like bridge devices and
similar which are created programmatically) that do not depend on any underlying hardware
should be allocated by the time this target is reached. It is not necessary for these
interfaces to also have completed IP level configuration by the time
<filename>network.target</filename> is reached.</para></listitem>
<listitem><para>At shutdown, a unit that is ordered after <filename>network.target</filename>
will be stopped before the network — to whatever level it might be set up by then — is shut
down. It is hence useful when writing service files that require network access on shutdown,
which should order themselves after this target, but not pull it in. Also see <ulink
url="https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget">Running Services After
the Network is up</ulink> for more information.</para></listitem>
</itemizedlist>
<para>It must emphasized that at start-up there's no guarantee that hardware-based devices have
shown up by the time this target is reached, or even acquired complete IP configuration. For that
purpose use <filename>network-online.target</filename> as described above.</para>
</listitem>
</varlistentry>
<varlistentry>