NAME

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

SYNOPSIS

       libnss_mymachines.so.2

DESCRIPTION

       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.

       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.

CONFIGURATION IN /ETC/NSSWITCH.CONF

       Here is an example /etc/nsswitch.conf file that enables nss-mymachines correctly:

           passwd:         files systemd
           group:          files [SUCCESS=merge] systemd
           shadow:         files 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

EXAMPLE: MAPPINGS PROVIDED BY NSS-MYMACHINES

       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.

SEE ALSO

       systemd(1), systemd-machined.service(8), machinectl(1), nss-systemd(8), nss-resolve(8),
       nss-myhostname(8), nsswitch.conf(5), getent(1)