This will fix on a standard installation, if you do manual partition, ask at the forum!

Boot up with our LiveIso.

mount System to /mnt

You need to know which device is the right one check with sudo fdisk -l

sudo su

/dev/sdXn should be replaced with the right device information, and depending on your installation you may have or have not a seperate /boot partition. If not /boot is a folder under / on the same partition as the filesystem root.

mount /dev/sdXn /mnt = / root partition

mount /dev/sdXn /mnt/boot = /boot partition –> without extra /boot partition you do not need this step!

mount /dev/sdXn /mnt/boot/efi = the EFI-boot (fat) partition

arch-chroot /mnt

BUT that grub is not in the boot list can be caused also by EFI-Boot-Settings not related to Grub and Antergos then, so re-/installing-/building grub may not solve your problem…

You can also make shure to get second (dual boot) installation rechecked and put into grub boot menu:

(as root also) If you have dualboot os-prober may takes a long long time to work, the trick here is to mount all other partitions, before using it.

grub-mkconfig -o /boot/grub/grub.cfg

Reinstall grub:

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=Antergos-grub

For legacy (bios) systems go here: https://antergos.com/wiki/miscellaneous/how-to-fix-grub-with-bios-boot/