how to restore mac air late 2010 to factory settings

If neither of these approaches work, it could be that your Ubuntu was installed in BIOS/CSM/legacy mode. This is less intimidating if you're not comfortable with text-mode command-line tools, but Boot Repair is overkill and runs a small risk of making matters worse, so I prefer to stick with efibootmgr as a first attempt. As an alternative to this, you could run Boot Repair. On a Mac, either should work but on the off chance that shim圆4.efi isn't installed, grub圆4.efi will work and is more direct. If you were using a UEFI-based PC, it would be safer to specify shim圆4.efi rather than grub圆4.efi. You can omit -d /dev/sda if that's the hard disk where GRUB is installed and -p 1 if your ESP is partition #1 and if your disk and/or partition are not those values, you must adjust the efibootmgr command appropriately. The command to do so is sudo efibootmgr -c -d /dev/sda -p 1 -l \EFI\ubuntu\grub圆4.efi -L ubuntu. If efibootmgr does not show an ubuntu entry, then you need to create a new one.refind-mkdefault -label ubuntu to set the Ubuntu entry as first. Alternatively, you could use the refind-mkdefault script described on my boot coup page, and that comes with rEFInd. If I'm right in my suspicion that you have an existing ubuntu entry, you can set it first by typing sudo efibootmgr -o #, where the first # is the number of the ubuntu entry and subsequent numbers are the remaining entries in the current boot order.At this point there are two possibilities:.Try again, but pick a different boot option for Ubuntu.) (If efibootmgr complains that it can't find EFI boot variables, then you've booted in BIOS/CSM/legacy mode. My suspicion is that one of these will be called ubuntu, but that the BootOrder will show a macOS entry as being first. This will show your current EFI boot options.

In a Terminal window, type sudo efibootmgr -v.Given your current situation, you may need to use an Ubuntu installation disk in its 'try before installing' mode or use my rEFInd boot manager on a USB flash drive or CD-R to boot into your regular Ubuntu on a one-time basis. See that page for details, but you can try this: It sounds like you're suffering from what I call a boot coup.

How to restore mac air late 2010 to factory settings