Six years on from Yosemite to Big Sur
Something has gone wrong with Preview, which doesn’t seem able to open PDFs properly any more. Thankfully, you’ve got a clone, so it’s easy to trash the app and replace it. But that doesn’t make matters any better, and now the Finder is playing up too.
You restart your Mac, but the problems remain. A quick check in Disk Utility finds a minor error in the file system, which you repair. You decide the best thing to do is to reinstall OS X, which restores normal function.
You don’t know, though, whether the disk error was to blame, or whether something else, either a wayward app or even malware, was at fault. After a scan with your anti-virus software, you presume it was just one of those things, and has been repaired anyway.
Your boot disk has two partitions, one of which contains OS X and all your data files in a fairly traditional hierarchy, with a journalled HFS+ file system which is known for its propensity to develop minor errors, and needs periodic maintenance to keep it in good shape. Every month or two, you let Disk Warrior rebuild the file system, to keep it in best form, and you may use a tool to defragment the disk as well. All that protects the system are standard Posix permissions, as System Integrity Protection has yet to come. Like all hard disks, yours occasionally develops an error, but doesn’t seem to be accumulating bad blocks.
