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.

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:         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

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)