Note that this NSS module only makes available names of the containers running immediately below the current system context. It does not provide host name resolution for containers running side-by-side with the invoking system context, or containers further up or down the container hierarchy. Or in other words, on the host system it provides host name resolution for the containers running immediately below the host environment. When used inside a container environment however, it will not be able to provide name resolution for containers running on the host (as those are siblings and not children of the current container environment), but instead only for nested containers running immediately below its own container environment.
To activate the NSS module, add "mymachines" to the line starting with "hosts:" in /etc/nsswitch.conf.
It is recommended to place "mymachines" before the "resolve" or "dns" entry of the "hosts:" line of /etc/nsswitch.conf in order to make sure that its mappings are preferred over other resolvers such as DNS.
passwd: compat systemd group: compat [SUCCESS=merge] systemd shadow: compat systemd gshadow: files systemd hosts: mymachines resolve [!UNAVAIL=return] files myhostname dns networks: files protocols: db files services: db files ethers: db files rpc: db files netgroup: nis
# systemd-nspawn -M rawhide --boot --network-veth --private-users=pick Spawning container rawhide on /var/lib/machines/rawhide. Selected user namespace base 20119552 and range 65536. ... $ machinectl --max-addresses=3 MACHINE CLASS SERVICE OS VERSION ADDRESSES rawhide container systemd-nspawn fedora 30 169.254.40.164 fe80::94aa:3aff:fe7b:d4b9 $ ping -c1 rawhide PING rawhide(fe80::94aa:3aff:fe7b:d4b9%ve-rawhide (fe80::94aa:3aff:fe7b:d4b9%ve-rawhide)) 56 data bytes 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 ... $ ping -c1 -4 rawhide PING rawhide (169.254.40.164) 56(84) bytes of data. 64 bytes from 169.254.40.164 (169.254.40.164): icmp_seq=1 ttl=64 time=0.064 ms ... # machinectl shell rawhide /sbin/ip a Connected to machine rawhide. Press ^] three times within 1s to exit session. 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 ... 2: host0@if21: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether 96:aa:3a:7b:d4:b9 brd ff:ff:ff:ff:ff:ff link-netnsid 0 inet 169.254.40.164/16 brd 169.254.255.255 scope link host0 valid_lft forever preferred_lft forever inet6 fe80::94aa:3aff:fe7b:d4b9/64 scope link valid_lft forever preferred_lft forever Connection to machine rawhide terminated.