Macbook Air M1 issues

I recently got my mom a Macbook Air M1, upgrading from a 2010 Macbook Pro (High Sierra).

When migrating over from High Sierra to Big Sur, using Migration Assistant (my Synology TimeMachine kept on failing — but besides that, migration went smoothly) two issues came up that required calling Apple.

But first off I noticed that when migrating, for some reason FileVault was turned off (more on that later). I, obviously, turned it on.

Problem A: when rebooting the Mac, I noticed the keyboard layout changed from Belgian (Azerty) to ABC (which is US English?) and it didn’t accept the password to unlock the Mac. You can manually select another keyboard layout which accepts the password, but at every reboot that resets and requires going back through the layout picker.

Solution A: M1 no longer supports the usual SMC or NVRAM reset. But this problem could be solved by turning off the mac, closing the lid (?!) and waiting 30+ seconds before turning it back on. According to the person on the phone, that’s the M1 SMC reset.

Problem B: I disabled guest mode in System Preferences > Users & Groups — but it was still showing alongside the regular/admin user. I don’t want guest mode.

Note that the guest mode only showed at the disk unlock (i.e.: after a reboot) and not when logged out (i.e.: Apple logo > Log Out from the regular user).

Solution B: Tried several things with Apple support:

• Turning off screen sharing and print sharing (sure — didn’t care too much about these)
• Turn guest mode on/off and reboot/force quite System preferences
• Turn off Find My in iCloud settings (not acceptable)
• Turn off FileVault (not acceptable)
• Manually running:
  • sudo defaults write /Library/Preferences/com.apple.AppleFileServer guestAccess -bool NO\n
  • sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.smb.server AllowGuestAccess -bool NO\n
• and a few other things I now forgot

This is what actually did help:

• Turning off FileVault actually turns off Guest mode; so when the Mac was not encrypted, it only showered one user (instead of the user + Guest) at the login prompt.
  • Obviously, that’s not acceptable and I turned it back on
• Supposedly turning off Find My in iCloud settings is needed (according to Apple this requires Guest mode)
  • I later turned it back on and Guest mode did not reappear. So, what Apple was saying was incorrect, and it does not make the Guest user show up.
• Running sudo fdesetup list in Terminal shows the list of users. This may be helpful for debugging.
• Running dscl . list /Users shows many users and included Guest in my mom’s case. Not entirely sure what I am looking at here.
• Running sudo dscl . delete /Users/Guest solved the problem. This deletes the Guest user (?).