To change the number of replicas for a an index, you can use the following one liner command:
curl -s -X PUT "localhost:9200/<IndexName>/_settings" -H 'Content-Type: application/json' -d' { "index" : { "number_of_replicas" : 1 } }'
You can also use a for loop to go over a list:
curl -s localhost:9200/_cat/indices?pretty | cut -d" " -f4 > all_indices
vi all_indices <==== If you need to pull some indices out
for i in $(cat all_indices); do curl -s -X PUT "localhost:9200/$i/_settings" -H 'Content-Type: application/json' -d' { "index" : { "number_of_replicas" : 1 } }'; done