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138 lines
6.6 KiB
XML
138 lines
6.6 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/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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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>Note that this NSS module only makes available names of the containers running immediately below
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the current system context. It does not provide host name resolution for containers running side-by-side
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with the invoking system context, or containers further up or down the container hierarchy. Or in other
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words, on the host system it provides host name resolution for the containers running immediately below
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the host environment. When used inside a container environment however, it will not be able to provide
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name resolution for containers running on the host (as those are siblings and not children of the current
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container environment), but instead only for nested containers running immediately below its own
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container environment.</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: files systemd
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group: files [SUCCESS=merge] systemd
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shadow: files systemd
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gshadow: files systemd
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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><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
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<member><citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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