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NAME | SYNOPSIS | DESCRIPTION | CONFIGURATION IN /ETC/NSSWITCH.CONF | EXAMPLE: MAPPINGS PROVIDED BY NSS-MYMACHINES | SEE ALSO | COLOPHON |
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NSS-MYMACHINES(8) nss-mymachines NSS-MYMACHINES(8)
nss-mymachines, libnss_mymachines.so.2 - Hostname resolution for
local container instances
libnss_mymachines.so.2
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.
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
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.
systemd(1), systemd-machined.service(8), machinectl(1),
nss-systemd(8), nss-resolve(8), nss-myhostname(8),
nsswitch.conf(5), getent(1)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 258~rc2 NSS-MYMACHINES(8)
Pages that refer to this page: org.freedesktop.machine1(5), systemd.directives(7), systemd.index(7), nss-myhostname(8), nss-resolve(8), nss-systemd(8), systemd-machined.service(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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