d296c20f1f
I am pretty sure /etc/hosts (i.e. an explicitly configured, local, trusted database) should be useful for overriding the automatic myhostname logic. resolved's internal logic handles it that way and hence we should suggest it in the NSS fallback line, too. Let's also bring the factory file back into sync with what the docs say. And update the prose a bit too, to actually match what we recommend.
128 lines
5.6 KiB
XML
128 lines
5.6 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
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<refentry id="nss-mymachines" conditional='ENABLE_NSS_MYMACHINES'>
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<refentryinfo>
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<title>nss-mymachines</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>nss-mymachines</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>nss-mymachines</refname>
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<refname>libnss_mymachines.so.2</refname>
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<refpurpose>Hostname resolution for local container instances</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>libnss_mymachines.so.2</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>nss-mymachines</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of
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the GNU C Library (<command>glibc</command>), providing hostname resolution for the names of containers running
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locally that are registered with
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<citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>. The
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container names are resolved to the IP addresses of the specific container, ordered by their scope. This
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functionality only applies to containers using network namespacing (see the description of
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<option>--private-network</option> in
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<citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
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Note that the name that is resolved is the one registered with <command>systemd-machined</command>, which
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may be different than the hostname configured inside of the container.</para>
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<para>To activate the NSS module, add <literal>mymachines</literal> to the line starting with
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<literal>hosts:</literal> in <filename>/etc/nsswitch.conf</filename>.</para>
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<para>It is recommended to place <literal>mymachines</literal> before the <literal>resolve</literal> or
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<literal>dns</literal> entry of the <literal>hosts:</literal> line of
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<filename>/etc/nsswitch.conf</filename> in order to make sure that its mappings are preferred over other
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resolvers such as DNS.</para>
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</refsect1>
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<refsect1>
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<title>Configuration in <filename>/etc/nsswitch.conf</filename></title>
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<para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables
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<command>nss-mymachines</command> correctly:</para>
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<!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf -->
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<programlisting>passwd: compat systemd
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group: compat [SUCCESS=merge] systemd
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shadow: compat
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hosts: <command>mymachines</command> resolve [!UNAVAIL=return] files myhostname dns
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networks: files
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protocols: db files
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services: db files
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ethers: db files
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rpc: db files
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netgroup: nis</programlisting>
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</refsect1>
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<refsect1>
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<title>Example: Mappings provided by <filename>nss-mymachines</filename></title>
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<para>The container <literal>rawhide</literal> is spawned using
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<citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>:
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</para>
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<programlisting># systemd-nspawn -M rawhide --boot --network-veth --private-users=pick
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Spawning container rawhide on /var/lib/machines/rawhide.
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Selected user namespace base 20119552 and range 65536.
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...
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$ machinectl --max-addresses=3
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MACHINE CLASS SERVICE OS VERSION ADDRESSES
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rawhide container systemd-nspawn fedora 30 169.254.40.164 fe80::94aa:3aff:fe7b:d4b9
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$ ping -c1 rawhide
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PING rawhide(fe80::94aa:3aff:fe7b:d4b9%ve-rawhide (fe80::94aa:3aff:fe7b:d4b9%ve-rawhide)) 56 data bytes
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64 bytes from fe80::94aa:3aff:fe7b:d4b9%ve-rawhide (fe80::94aa:3aff:fe7b:d4b9%ve-rawhide): icmp_seq=1 ttl=64 time=0.045 ms
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...
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$ ping -c1 -4 rawhide
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PING rawhide (169.254.40.164) 56(84) bytes of data.
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64 bytes from 169.254.40.164 (169.254.40.164): icmp_seq=1 ttl=64 time=0.064 ms
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...
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# machinectl shell rawhide /sbin/ip a
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Connected to machine rawhide. Press ^] three times within 1s to exit session.
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1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
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...
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2: host0@if21: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
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link/ether 96:aa:3a:7b:d4:b9 brd ff:ff:ff:ff:ff:ff link-netnsid 0
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inet 169.254.40.164/16 brd 169.254.255.255 scope link host0
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valid_lft forever preferred_lft forever
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inet6 fe80::94aa:3aff:fe7b:d4b9/64 scope link
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valid_lft forever preferred_lft forever
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Connection to machine rawhide terminated.
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</programlisting>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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