How to backup your controlfile to trace

SQL> ALTER DATABASE BACKUP CONTROLFILE TO TRACE AS '/fullpath/backup_controlfile.trc' [REUSE] [RESETLOGS | NORESETLOGS];

Note that if you do not specify either RESETLOGS or NORESETLOGS during the create command, oracle will include both versions in the resulting file, and you must pick the appropriate one for your situation.

REUSE will generate a backup controlfile statement which includes the REUSE keyword.
This in turn, indicates that when the "create controlfile" command is executed, you can reuse the existing physical control files on your server. If you don't, and the file exists from a previous database incarnation, Oracle will throw an error, so I prefer to leave it there.