...
c.PAMAuthenticator.open_sessions = False
c.LocalAuthenticator.create_system_users = True
c.PAMAuthenticator.add_user_cmd = ['adduser', '-m']

# ldap
c.JupyterHub.authenticator_class = 'ldapcreateusers.LocalLDAPCreateUsers'
c.LDAPAuthenticator.server_address = 'ldap://localhost'
c.LDAPAuthenticator.use_ssl = False
c.LDAPAuthenticator.bind_dn_template = [
    "cn={username},ou=People,dc=x,dc=com",
]
c.LDAPAuthenticator.allowed_groups = [
    "cn=jupyter,ou=Group,dc=x,dc=com",
]

    ...
    def add_system_user(self, user):
        """Create a new local UNIX user on the system.

        Tested to work on FreeBSD and Linux, at least.
        """
        #self.add_user_cmd = ['adduser', '-m']
        self.log.info(f"\n\ncmd : {self.add_user_cmd}\n")  # debug

        name = user.name
        cmd = [arg.replace('USERNAME', name) for arg in self.add_user_cmd]
        ...