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srm

Towards the end of last year, I learnt that OS X provided the option to securely delete files from Trash. Normally a regular delete is fine and, indeed, it could be invaluable if I find I’ve accidentally zapped a photo or other file that I really should have kept – deleting from Trash on a Mac (or Windows) makes the file harder to recover but not automatically impossible. However, there are times where a more thorough expunging of data is called for.

One of those is when I’ve received information in an encrypted form, like a password reset for one of the users at work, and I’ve unencrypted it to print out a copy to hand to them. What to do with the file now its work has been done. Although the chance of someone running recovery tools on my system before the user has re-activated the account (and created a new password which isn’t written down) is miniscule, I should do these things properly.

It turns out that ‘Securely Empty Trash’ is no longer available in El Capitan, the latest version of OS X which I upgraded to in December. After a little research, it turns out that it didn’t securely work on all systems (and perhaps too many people complained after deleting files and not being able to pay through the nose for a data recovery company to undo their mistake?). However, there is a command line tool to do the the job and, for a dyed-in-the-wool geek like me, that is just dandy.

So that gets us to the meaning of the cryptic post title. If you are on a Mac running the current version of the system and you want to securely remove a file, use srm (secure remove, natch) on the command line. That strikes me as quite an elegant solution – it is a serious tool and the command line is a serious environment (sometimes terminal! You’ll have to be prompt to get that one); if you are going to scrub a file, then you need to learn a little more about how to go under the hood and that will stand you in good stead for many tasks.

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