I am at the point where I am about to erase the HD on my old iMac 2009 running El Cap before selling it.
I recently turned on FileVault to encrypt the volume mainly to see how it worked and also as an aide to what I thought was going to be a quick and secure erasure of that HD.
I have reached this point following these instructions on MacWorld:
With a FileVault-encrypted startup disk, you can restart into OS X Recovery and launch Disk Utility to erase the volume. However, before erasing, you need to select the disk and then choose File > Unlock “volume name”. Enter the password for any FileVault-enabled user account, and the disk is unlocked and can be erased.
When I choose Erase, the next window gives me the warning: Are you sure you want to erase the partition “Macintosh HD” and create an encrypted partition? Warning: Files on this partition will be encrypted using this password. If you forget the password, your data will be lost.
It's either cancel, and then I can't erase my HD or continue.
Not sure what I am doing at this point and could use some help.
Am I setting up FileVault for the next owner of this iMac?
What does the message in this window really mean?