libnss_systemd.so.2 (8) - Linux Man Pages
libnss_systemd.so.2: Provide UNIX user and group name resolution for user/group lookup via Varlink
nss-systemd, libnss_systemd.so.2 - Provide UNIX user and group name resolution for user/group lookup via Varlink
nss-systemd is a plug-in module for the GNU Name Service Switch (NSS) functionality of the GNU C Library (glibc), providing UNIX user and group name resolution for services implementing the m[blue]User/Group Record Lookup API via Varlinkm, such as the system and service manager systemd(1) (for its DynamicUser= feature, see systemd.exec(5) for details) or systemd-homed.service(8).
This module also ensures that the root and nobody users and groups (i.e. the users/groups with the UIDs/GIDs 0 and 65534) remain resolvable at all times, even if they aren't listed in /etc/passwd or /etc/group, or if these files are missing.
This module preferably utilizes systemd-userdbd.service(8) for resolving users and groups, but also works without the service running.
To activate the NSS module, add "systemd" to the lines starting with "passwd:" and "group:" in /etc/nsswitch.conf.
Here is an example /etc/nsswitch.conf file that enables nss-systemd correctly:
passwd: compat mymachines systemd group: compat [SUCCESS=merge] mymachines [SUCCESS=merge] 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
User/Group Record Lookup API via Varlink