I heard rave reviews of Time Machine before I got a Mac. After setting it up though, I found that it only backs up user files. It doesn’t actually backup OS files. Thus, if something you install messes up your O/S files, it won’t help.
So it looks like Syncthing set to mirror the user directory is much the same.
But technically, Time Machine is supposed to be a proper backup solution, whereas Syncthing is supposed to be just for Sync.
Is there any point running both of Time Machine AND Syncthing?
Is there a way to use Syncthing to backup O/S files so that if I mess up a kext, I can fix it?
Certainly there’s a point. Time Machine lets you restore files to a previous point in time after you screwed up and made a mess of something. Syncthing just shuffles those messed up files to somewhere else.
No. Apart from probably several other problems, Syncthing doesn’t transfer ownership or extended attributes, which you’d probably need in order to back up a macOS installation properly.
I’ve never used it myself, but I’ve heard positive things about SuperDuper from those who want a full system copy / backup of their Mac.
Note: With the last couple of OS releases, the core OS itself is not backed up via Time Machine - it’s on a read-only volume has to be restored from Recovery Disk. However, all the user-installed kext files will get covered with Time Machine.
Even if it doesn’t back up all OS files, that’s a technicality. I routinely use the Migration assistant on a new Mac to recover setup from a Time Machine backup, and it works flawlessly. By that I mean not just recover a few files, but to recover the whole computer to where it was at the time of the last TM backup, apps, settings, data - the lot.
In fact, I use it to configure machines for my Workplace: I have a standard staff configuration that I’ve backed up with TM, and step 1 for every new machine that comes through the door is to recover that from the TM backup. Another half hour of customising and the machine setup is done.
The only situation I’ve had problems with is recovering a later OSX version backup to an earlier OSX version. But the solution is simple there - upgrade.
Oh, and you do need to go through and reassign app security access settings. But I’d count that as a plus.
Syncthing in itself is still not a backup tool. The remote copy (which you call backup) might very well be updated fast by Syncthing. But it is equally fast destroyed in case your computer is hit by ransomware.