Quick-fire questions

How can I fix the sudo bug in High Sierra?

> Apple has released security updates for Mojave, Catalina and Big Sur which fix this bug. Macs running an older version of macOS will still be vulnerable and there’s no official update on offer. Installer packages for older versions of macOS are available from Todd Miller’s site at bit.ly/mac365sudo.

Why do some image thumbnails

look rubbish?

> QuickLook builds an initial thumbnail very quickly, but that may contain Moiré noise which can deface images. A few seconds later, that first attempt should be replaced with a higher-quality version, so the noise should then vanish. There’s nothing you control which can change that.

How can I change my long and short usernames?

> Don’t try this unless it’s essential. Although there are commands intended to make this work, many features of macOS and apps depend on knowing your short username to access the Home folder. Although they shouldn’t suffer if you do, in practice you’ll waste time fixing everything that this breaks. You’ll need to log in as a different user, open the Users & Groups pane, then ≈-click on the user whose name you want to change. The contextual menu offers Advanced Options which allow you to do that, if you must.

Why is my Mac’s Gatekeeper so out of date?

> If your Mac was running at the time of the last update to Gatekeeper’s data in the autumn of 2019, then it should still show the latest version as 181. Apple stopped updating that data with the release of Catalina, and Macs which have never known any earlier release now show version 94 from August 2016. It’s no longer used, and there’s no way to update it either.