Delete old announcement and update corefile page.

Could still do with some work.

Author: CallumWalley

docs/General/Announcements/Mahuika-Core_Dumps_generation_now_disabled_as_default.md

@@ -2,24 +2,28 @@
 created_at: '2020-06-25T01:10:40Z'
 tags:
 - corefile
-- coredump
+- troubleshooting
 title: What is a '.core' file?
-vote_count: 0
-vote_sum: 0
-zendesk_article_id: 360001584875
-zendesk_section_id: 360000039036
 ---
 
-.core files are created when a program fails in a way that can't be
-handled by the program's regular error handling. Normally these failures
-are memory-related, such as the program asking for too much memory or
-for memory it can't legally access. The creation of a core file is
-called a 'core dump'.
+`.core` files are created when a program fails in a way that can't be
+handled by the program's regular error handling.
 
-.core files are a record of the working memory at time of failure, and
+Your application may crash with an error like, `Segmentation fault (core dumped)`.
+
+These failures are memory-related, such as the program asking for more memory than allocated or
+for memory it can't legally access.
+Your first step in troubleshooting should be checking if this is the case,
+see [Finding Job_Efficiency](../../Getting_Started/Next_Steps/Finding_Job_Efficiency.md)
+
+`.core` files are a record of the working memory at time of failure, and
 can be used for
 [debugging](../../Scientific_Computing/Profiling_and_Debugging/Debugging.md).
-MPI jobs will usually create a .core file for each task.
+MPI jobs will usually create a `.core` file for each task.
+
+The creation of a `.core` file is called a 'core dump' is files is **disabled by default**,
+
+You can enable the creation of core dumps with `ulimit -c unlimited`.
 
-As .core files are usually very large, you should delete the ones you
-don't plan on using them to avoid filling up your storage quota.
+As `.core` files are large, you should delete the ones you
+don't plan on using them to avoid filling up your storage quota.