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.
My latest blog post: Deontology vs Consequentialism: If we have free speech, personal freedom, equality, and truthfulness we are off to a pretty good start. (posted 2025-10-20). Warning: mysqli_connect(): MySQL server has gone away in /Library/WebServer/Documents/Owen2/Inc/Footer.m.inc.php on line 51
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