Recently I have been performing multiple Oracle 12c RAC setups and digging deep into ASM internals. Besides query the ASM environment via the V$ASM_DISK and V$ASM_DISKGROUP dynamic tables, these lesser known command line tools provide detailed troubleshooting assistance for solving difficult ASM issues with your Oracle environments.
As a reference point for today's discussion, I found a very useful support note from Oracle that explains all three utilities to analyze Oracle ASM environments:
Kfod is a quick and dirty tool to examine the current ASM configuration for ownership, sizes and device mappings. Ensure that your kfod is in the local path for $GRID_HOME/bin/kfod to allow execution of the tool.
To get help with kfod use the help=y option: