1NSS-MYMACHINES(8)               nss-mymachines               NSS-MYMACHINES(8)
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NAME

6       nss-mymachines, libnss_mymachines.so.2 - Hostname resolution for local
7       container instances
8

SYNOPSIS

10       libnss_mymachines.so.2
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DESCRIPTION

13       nss-mymachines is a plug-in module for the GNU Name Service Switch
14       (NSS) functionality of the GNU C Library (glibc), providing hostname
15       resolution for the names of containers running locally that are
16       registered with systemd-machined.service(8). The container names are
17       resolved to the IP addresses of the specific container, ordered by
18       their scope. This functionality only applies to containers using
19       network namespacing (see the description of --private-network in
20       systemd-nspawn(1)). Note that the name that is resolved is the one
21       registered with systemd-machined, which may be different than the
22       hostname configured inside of the container.
23
24       Note that this NSS module only makes available names of the containers
25       running immediately below the current system context. It does not
26       provide host name resolution for containers running side-by-side with
27       the invoking system context, or containers further up or down the
28       container hierarchy. Or in other words, on the host system it provides
29       host name resolution for the containers running immediately below the
30       host environment. When used inside a container environment however, it
31       will not be able to provide name resolution for containers running on
32       the host (as those are siblings and not children of the current
33       container environment), but instead only for nested containers running
34       immediately below its own container environment.
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36       To activate the NSS module, add "mymachines" to the line starting with
37       "hosts:" in /etc/nsswitch.conf.
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39       It is recommended to place "mymachines" before the "resolve" or "dns"
40       entry of the "hosts:" line of /etc/nsswitch.conf in order to make sure
41       that its mappings are preferred over other resolvers such as DNS.
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CONFIGURATION IN /ETC/NSSWITCH.CONF

44       Here is an example /etc/nsswitch.conf file that enables nss-mymachines
45       correctly:
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47           passwd:         compat systemd
48           group:          compat [SUCCESS=merge] systemd
49           shadow:         compat systemd
50           gshadow:        files systemd
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52           hosts:          mymachines resolve [!UNAVAIL=return] files myhostname dns
53           networks:       files
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55           protocols:      db files
56           services:       db files
57           ethers:         db files
58           rpc:            db files
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60           netgroup:       nis
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EXAMPLE: MAPPINGS PROVIDED BY NSS-MYMACHINES

63       The container "rawhide" is spawned using systemd-nspawn(1):
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65           # systemd-nspawn -M rawhide --boot --network-veth --private-users=pick
66           Spawning container rawhide on /var/lib/machines/rawhide.
67           Selected user namespace base 20119552 and range 65536.
68           ...
69
70           $ machinectl --max-addresses=3
71           MACHINE CLASS     SERVICE        OS     VERSION ADDRESSES
72           rawhide container systemd-nspawn fedora 30      169.254.40.164 fe80::94aa:3aff:fe7b:d4b9
73
74           $ ping -c1 rawhide
75           PING rawhide(fe80::94aa:3aff:fe7b:d4b9%ve-rawhide (fe80::94aa:3aff:fe7b:d4b9%ve-rawhide)) 56 data bytes
76           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
77           ...
78           $ ping -c1 -4 rawhide
79           PING rawhide (169.254.40.164) 56(84) bytes of data.
80           64 bytes from 169.254.40.164 (169.254.40.164): icmp_seq=1 ttl=64 time=0.064 ms
81           ...
82
83           # machinectl shell rawhide /sbin/ip a
84           Connected to machine rawhide. Press ^] three times within 1s to exit session.
85           1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
86               ...
87           2: host0@if21: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
88               link/ether 96:aa:3a:7b:d4:b9 brd ff:ff:ff:ff:ff:ff link-netnsid 0
89               inet 169.254.40.164/16 brd 169.254.255.255 scope link host0
90                  valid_lft forever preferred_lft forever
91               inet6 fe80::94aa:3aff:fe7b:d4b9/64 scope link
92                  valid_lft forever preferred_lft forever
93           Connection to machine rawhide terminated.
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SEE ALSO

96       systemd(1), systemd-machined.service(8), machinectl(1), nss-systemd(8),
97       nss-resolve(8), nss-myhostname(8), nsswitch.conf(5), getent(1)
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101systemd 250                                                  NSS-MYMACHINES(8)
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