Designating and starting a search head captain

The first time you bring up the search head cluster, you will need to execute a command on one of the search heads to trigger the cluster into electing a captain; the server_list in this command is a scheme:ipaddress:mgmt_port list of all your search heads, separated by commas and enclosed in quotes:

./splunk bootstrap shcluster-captain -servers_list "https://172.31.28.137:8089,https://172.31.46.250:8089,https://172.31.1.45:8089" -auth admin:Splunk1t2me