I'll reply to my own message because I've finally found the command which works for me.
./keytool -export -storetype JCEKS -storepass password -keystore /opt/keystore/certificates.ks -alias http -file http.cer
I'll reply to my own message because I've finally found the command which works for me.
./keytool -export -storetype JCEKS -storepass password -keystore /opt/keystore/certificates.ks -alias http -file http.cer