NAMEnss-resolve, libnss_resolve.so.2 - Provide hostname resolution via systemd-resolved.service
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.
It is recommended to place "resolve" early in /etc/nsswitch.conf' "hosts:" line (but after the "files" or "mymachines" entries), replacing the "dns" entry if it exists, to ensure DNS queries are always routed via systemd-resolved(8).
Note that nss-resolve will chain-load nss-dns if systemd-resolved.service is not running, ensuring that basic DNS resolution continues to work if the service is down.
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
This keeps the dns module as a fallback for cases where the nss-resolve module is not installed.