nss-mymachines is a plug-in module for the GNU Name Service Switch (NSS) functionality of the GNU C Library (glibc), providing hostname resolution for the names of containers running locally that are registered with systemd-machined.service(8). The container names are resolved to the IP addresses of the specific container, ordered by their scope. This functionality only applies to containers using network namespacing (see the description of --private-network in systemd-nspawn(1)). Note that the name that is resolved is the one registered with systemd-machined, which may be different than the hostname configured inside of the container.
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.
Here is an example /etc/nsswitch.conf file that enables nss-mymachines correctly:
passwd: compat systemd group: compat [SUCCESS=merge] systemd shadow: compat hosts: mymachines resolve [!UNAVAIL=return] files myhostname dns networks: files protocols: db files services: db files ethers: db files rpc: db files netgroup: nis
The container "rawhide" is spawned using systemd-nspawn(1):
# 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.