This command will show you your jmap path. Using the path, you can use a jvm heap dump command like the following.
/home/oracle/Middleware/jdk160_24/bin/jmap -dump:file=/home/icfun/dump.bin 23968
here 23968 is the pid. To find a pid for your running java process, use the following command.
ps ax | grep java
This command will display a list of running java processes from your linux.
You may encounter errors while taking heap dump using jmap. One error can be:
23968: well-known file is not secure
This can cause if your running process and the heap dump output file belongs to different users. For example if /home/icfun/dump.bin belongs to the root user and the pid 23968 belongs to the oracle user. Better change the output dump file directory in such a way that it belongs to the oracle user(or the user that is same to your pid). Also try to run the jmap dump command using the oracle user.