While installing DB2 pureScale, if you receive the error: DBT3542E An instance management task failed because the db2prereqcheck utility encountered an internal error. Reason code: "2", the fix is simple.
Edit your /etc/hosts file and check if you have tabs separating the entries in the file. Replace those tabs with spaces and you should be good to go. It looks that the db2prereqcheck did not do a good job of parsing the /etc/hosts properly.