Description¶

nss-resolve is a plug-in module for the GNU Name Service Switch (NSS) functionality of the GNU C Library (glibc) enabling it to resolve host names via the systemd-resolved(8) local network name resolution service. It replaces the nss-dns plug-in module that traditionally resolves hostnames via DNS.

To activate the NSS module, add "resolve" to the line starting with "hosts:" in /etc/nsswitch.conf. Specifically, it is recommended to place "resolve" early in /etc/nsswitch.conf's "hosts:" line (but after the "files" or "mymachines" entries), right before the "dns" entry if it exists, followed by "[!UNAVAIL=return]", to ensure DNS queries are always routed via systemd-resolved(8) if it is running, but are routed to nss-dns if this service is not available.

Note that systemd-resolved will synthesize DNS resource records in a few cases, for example for "localhost" and the current hostname, see systemd-resolved(8) for the full list. This duplicates the functionality of nss-myhostname(8), but it is still recommended (see examples below) to keep nss-myhostname configured in /etc/nsswitch.conf, to keep those names resolveable if systemd-resolved is not running.

Example¶

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

passwd:         compat mymachines systemd
group:          compat mymachines systemd
shadow:         compat

hosts:          files mymachines resolve [!UNAVAIL=return] dns myhostname
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

See Also¶

systemd(1), systemd-resolved(8), nss-systemd(8), nss-myhostname(8), nss-mymachines(8), nsswitch.conf(5)