The `srm` that used to ship with MacOS doesn't work with SSDs. It worked by overwriting, renaming, and truncating the file before unlinking it. On rotational

The `srm` that used to ship with MacOS doesn't work with SSDs. It worked by overwriting, renaming, and truncating the file before unlinking it. On rotational HDs, the overwrites clobber the data in the same physical location on disk. On SSDs, the overwrites will typically appear in a new location on disk due to wear-leveling and block-sparing. Your best bet is to turn on FileVault, wait for it to finish encrypting the drive, then wipe the whole disk in Recovery Mode.