SYSTEMD-USERDBD.SERVICE(8) systemd-userdbd.service SYSTEMD-USERDBD.SERVICE(8) systemd-userdbd.service, systemd-userdbd - / JSON/ NSS systemd-userdbd.service /usr/lib/systemd/systemd-userdbd systemd-userdbd / / JSON . / JSON / UNIX/glibc NSS . / /etc/userdb/ /run/userdb/ /run/host/userdb/ /usr/lib/userdb/ ".user" ".group". nss-systemd(8). systemd-userdbd userdbctl(1). JSON User Records[1] JSON Group Record[2]. User/Group Record Lookup API via Varlink[3] . . Varlink[4] : io.systemd.Multiplexer JSON. / . . io.systemd.NameServiceSwitch UNIX/glibc NSS struct passwd struct group getpwnam(1) / JSON . io.systemd.DropIn / JSON . systemd(1), nss-systemd(8), userdbctl(1), systemd-homed.service(8) 1. JSON https://systemd.io/USER_RECORD 2. JSON https://systemd.io/GROUP_RECORD 3. / Varlink https://systemd.io/USER_GROUP_API 4. Varlink https://varlink.org/ 3 . . : . systemd 260.2 SYSTEMD-USERDBD.SERVICE(8)