where is core-default.xml file?

I'm interested in value of fs.s3a.connection.ssl.enabled parameter in my mapr cluster.

I know the value is set in core-default.xml (if not overwritten by core-site.xml) but I cannot find core-default.xml file. Any suggestions where it can be?

Is there any way to check the current value of parameter?

where is core-default.xml file?

It is in resources of hadoop-common; https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/resources/core-default.xml

So in this case you will be able to find it inside jar file of hadoop-common; the jar can be found in /opt/mapr/hadoop/hadoop-<version>/share/hadoop/common/hadoop-common-<version>.jar

I have extracted the jar and list the files;

[... ~]$ jar xf ./hadoop-common-<version>.jar
[... ~]$ ll
-rw-rw-r--  1  mapr mapr   1041 Mar 15 18:36 common-version-info.properties
-rw-rw-r--  1  mapr mapr  64287 Mar 15 18:06 core-default.xml
...

Is there any way to check the current value of parameter?

Yes there is. In order to grep the property by means of hadoop utilities, please run the following command;

hadoop org.apache.hadoop.conf.Configuration | grep "fs.s3a.connection.ssl.enabled"