In an Icinga2 master + satellite + director setup, configuration are first pushed on every master and satellites, then the configuration is checked against the current configuration on each node.
Sometimes, the satellite (or master) may yield the warning message :
critical/ApiListener: Config validation failed for staged cluster config sync in '/var/lib/icinga2/api/zones-stage/'. Aborting. Logs: '/var/lib/icinga2/api/zones-stage//startup.log'
The startup.log logfile may be empty or absent.
If so, you can test the staged (pending) configuration and get the error messages with the following command:
icinga2 --no-stack-rlimit daemon --close-stdio -e /var/log/icinga2/error.log --validate --define System.ZonesStageVarDir=/var/lib/icinga2/api/zones-stage/