On starting sssd

there. At first, it says the daemon couldn't find the /etc/sssd/sssd.conf. So, I created this and, when executing sssd "systemctl start sssd.service", it shows the following errors.

Jun 25 21:00:48 tmax1 sssd[nss]: Starting up
Jun 25 21:00:48 tmax1 sssd[nss]: Starting up
Jun 25 21:00:48 tmax1 sssd[pam]: Starting up
Jun 25 21:00:48 tmax1 sssd[pam]: Starting up
Jun 25 21:00:49 tmax1 sssd[be[DOMAIN.COM]]: Starting up
Jun 25 21:00:49 tmax1 sssd: Exiting the SSSD. Could not restart critical service [DOMAIN.COM].
Jun 25 21:00:49 tmax1 systemd: sssd.service: main process exited, code=exited, status=1/FAILURE
Jun 25 21:00:49 tmax1 systemd: Failed to start System Security Services Daemon.
Jun 25 21:00:49 tmax1 systemd: Unit sssd.service entered failed state.
Jun 25 21:00:49 tmax1 systemd: sssd.service failed.

Is there any other configuration file or something to check before running sssd? I can check the realm by "realm discover DOMAIN.COM". Ping is fine.

[test1@ ~]$ realm discover domain.com
domain.com
  type: kerberos
  realm-name: DOMAIN.COM
  domain-name: domain.com
  configured: no
  server-software: active-directory
  client-software: sssd
  required-package: oddjob
  required-package: oddjob-mkhomedir
  required-package: sssd
  required-package: adcli
  required-package: samba-common-tools

Sometimes, the "kinit" command doesn't work, but I can see the ticket by the "klist" only with the root account.

[test1@ ~]$ klist
klist: Credentials cache keyring 'persistent:1000:1000' not found

[root@ ~]# klist
Ticket cache: KEYRING:persistent:0:0
Default principal: administrator@DOMAIN.COM

Valid starting       Expires              Service principal
06/25/2018 17:08:47  06/26/2018 03:08:47  krbtgt/DOMAIN.COM@DOMAIN.COM
	renew until 07/02/2018 17:08:45

What do I do more to start sssd..? Thank you.