userdb unix_listen .dovecot-userdb

c = ./dovecot-auth-cli .dovecot exists username

userdb -> VERSION	1	1
userdb -> SPID	12345

userdb <- VERSION	1	1
userdb <- USER	1	username	service=smtp

userdb -> USER	1	username	system_groups_user=blah uid=10  gid=10

c <- yes
c wait 0