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

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)

systemd 258						     NSS-MYMACHINES(8)