# nss-mymachines

## 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.
    


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