To secure erase when that option isn't available in Disk Utility. For example, for SSDs. Boot from another disk or recovery mode. Erase the disk encrypted, with a complex key. Fill the disk with zeros. Erase it again, without encryption or with a different key.
Options to fill with zeros
If it is available, use mkfile, otherwise use dd...
mkfile SIZE FILE Example: mkfile 200G File1 dd if=/dev/zero of=FILE bs=BLOCKSIZE count=BLOCKS Example: dd if=/dev/zero of=File1 bs=1024 count=1000000 Warning: don't make bs too small or the process will be very slow.
I usually write a blog post about once a week. The latest post can be viewed here: Are We the Baddies?: Maybe you should ask yourself: are we the baddies? (posted 2025-11-24 at 17:01:10). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2025-11-06 Democracy v Bureaucracy: It's not left versus right which I am complaining about: it is bureaucracy versus democracy!.
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