[root@vml000117 features-enabled]# systemctl status icinga2.service
● icinga2.service - Icinga host/service/network monitoring system
   Loaded: loaded (/usr/lib/systemd/system/icinga2.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2017-03-06 20:36:14 CET; 1s ago
  Process: 30906 ExecStart=/usr/sbin/icinga2 daemon -d -e ${ICINGA2_ERROR_LOG} (code=exited, status=0/SUCCESS)
  Process: 30842 ExecStartPre=/usr/lib/icinga2/prepare-dirs /etc/sysconfig/icinga2 (code=exited, status=0/SUCCESS)
 Main PID: 30932 (icinga2)
   CGroup: /system.slice/icinga2.service
           ├─30927 /usr/lib64/icinga2/sbin/icinga2 --no-stack-rlimit daemon -d -e /var/log/icinga2/error.log
           └─30932 /usr/lib64/icinga2/sbin/icinga2 --no-stack-rlimit daemon -d -e /var/log/icinga2/error.log

Mar 06 20:36:14 vml000117.dmz.nausch.org systemd[1]: Starting Icinga host/service/network monitoring system...
Mar 06 20:36:14 vml000117.dmz.nausch.org systemd[1]: Started Icinga host/service/network monitoring system.
[root@vml000117 features-enabled]# icinga2 api setup
information/cli: Generating new CA.
information/base: Writing private key to '/var/lib/icinga2/ca/ca.key'.
information/base: Writing X509 certificate to '/var/lib/icinga2/ca/ca.crt'.
information/cli: Generating new CSR in '/etc/icinga2/pki/vml000117.dmz.nausch.org.csr'.
information/base: Writing private key to '/etc/icinga2/pki/vml000117.dmz.nausch.org.key'.
information/base: Writing certificate signing request to '/etc/icinga2/pki/vml000117.dmz.nausch.org.csr'.
information/cli: Signing CSR with CA and writing certificate to '/etc/icinga2/pki/vml000117.dmz.nausch.org.crt'.
information/pki: Writing certificate to file '/etc/icinga2/pki/vml000117.dmz.nausch.org.crt'.
information/cli: Copying CA certificate to '/etc/icinga2/pki/ca.crt'.
information/cli: API user config file '/etc/icinga2/conf.d/api-users.conf' already exists, not creating config file.
information/cli: Enabling the 'api' feature.
Enabling feature api. Make sure to restart Icinga 2 for these changes to take effect.
Done.

Now restart your Icinga 2 daemon to finish the installation!

[root@vml000117 features-enabled]# systemctl restart icinga2.service 
[root@vml000117 features-enabled]# systemctl status icinga2.service
● icinga2.service - Icinga host/service/network monitoring system
   Loaded: loaded (/usr/lib/systemd/system/icinga2.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2017-03-06 20:37:07 CET; 1s ago
  Process: 31131 ExecStart=/usr/sbin/icinga2 daemon -d -e ${ICINGA2_ERROR_LOG} (code=exited, status=0/SUCCESS)
  Process: 31068 ExecStartPre=/usr/lib/icinga2/prepare-dirs /etc/sysconfig/icinga2 (code=exited, status=0/SUCCESS)
 Main PID: 31157 (icinga2)
   CGroup: /system.slice/icinga2.service
           ├─31152 /usr/lib64/icinga2/sbin/icinga2 --no-stack-rlimit daemon -d -e /var/log/icinga2/error.log
           └─31157 /usr/lib64/icinga2/sbin/icinga2 --no-stack-rlimit daemon -d -e /var/log/icinga2/error.log

Mar 06 20:37:06 vml000117.dmz.nausch.org systemd[1]: Starting Icinga host/service/network monitoring system...
Mar 06 20:37:07 vml000117.dmz.nausch.org systemd[1]: Started Icinga host/service/network monitoring system.